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How Antimatter Spacecraft Will Work

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"Engineering, stand by for warp drive." With that command, the "Star Trek" crew of the U.S.S. Enterprise prepared to hurl the spaceship through the cosmos at superluminal speeds.

Warp drive is one of those science-fiction technologies, like teleportation and time travel , that have some scientific basis. We just haven't achieved it yet. However, scientists are working on developing an interstellar spacecraft engine that is similar to the antimatter engine of the Enterprise.

­No engine is likely to generate superluminal speeds; the laws of physics prevent us from doing that, but we will be able to go many times faster than our current propulsion methods allow. A matter-antimatter engine will take us far beyond our solar system and let us reach nearby stars in a fraction of the time it would take a spacecraft propelled by a liquid-hydrogen engine , like the one used in space shuttles .

It's like the difference between driving an Indy race car and a 1971 Ford Pinto: In the Pinto, you'll eventually get to the finish line, but it will take 10 times longer than in the Indy car.

Let's peer a few decades into the future of space travel to look at an antimatter spacecraft and find out what antimatter actually is and how we might use it for an advanced propulsion system.

What is Antimatter?

Antimatter particles at work, the role of particle detectors, so why no matter-antimatter reaction engine, matter-antimatter engine.

This isn't a trick question. Antimatter is exactly what you might think it is — the opposite of normal matter, of which the majority of our universe is made. At one point, scientists considered the presence of antimatter in our universe as only theoretical.

British physicist Paul Dirac helped change our understanding of antimatter.

In 1928, he revised Einstein's famous equation E = mc² . Dirac said that Einstein didn't consider that the "m" in the equation — mass — could have negative energy as well as positive energy. Dirac's equation (E = + or - mc²) allowed for the existence of anti-particles in our universe. Scientists have since proven that several anti-particles exist.

These anti-particles are, literally, mirror images of normal matter. Each anti-particle has the same mass as its corresponding particle, but the electrical charges are reversed. Here are some antimatter discoveries of the 20th century:

• Positrons : Electrons with a positive instead of a negative charge. Discovered by Carl Anderson in 1932, positrons were the first evidence that antimatter existed.
• Anti-protons : Protons that have a negative instead of the usual positive charge. In 1955, researchers at the Berkeley Bevatron produced an antiproton.
• Anti-atoms : Pairing together positrons and antiprotons, scientists at CERN , the European Organization for Nuclear Research, created the first anti-atom. Nine anti-hydrogen atoms were created, each lasting only 40 nanoseconds. As of 1998, CERN researchers were pushing the production of anti-hydrogen atoms to 2,000 per hour.

When antimatter comes into contact with normal matter, these equal but opposite particles collide to produce an explosion emitting pure radiation, which travels out of the point of the explosion at the speed of light. Both particles that created the explosion are completely annihilated, leaving behind other subatomic particles.

The explosion that occurs when matter and antimatter meet transfers the entire mass of both objects into energy. Scientists believe that this energy is more powerful than any that can be generated by other propulsion methods.

Antimatter in the Universe

Gamma rays and cosmic rays are high-energy particles and radiation that originate from various sources in the universe, such as supernovae, black holes and even the Big Bang itself. Scientists theorize that antimatter should be as abundant as ordinary matter because of the Big Bang, but it's scarcely observed in our universe.

A particle detector is an essential tool in the field of particle physics. They enable scientists to identify and study subatomic particles, including those made of antimatter, as they interact with matter. By capturing and analyzing particle interactions, detectors help scientists understand fundamental particle properties and investigate the universe's origins.

The problem with developing antimatter propulsion is that there is a lack of antimatter existing in the universe. If there were equal amounts of matter and antimatter, we would likely see these reactions around us. Since antimatter doesn't exist around us, we don't see the light that would result from it colliding with matter.

It is possible that particles outnumbered anti-particles at the time of the Big Bang. As stated above, the collision of particles and anti-particles destroys both. And because there may have been more particles in the universe to start with, those are all that's left. There may be no naturally existing anti-particles in our universe today.

However, scientists discovered a possible deposit of antimatter near the center of the galaxy in 1977. If that does exist, it would mean that antimatter exists naturally, and the need for antimatter production would no longer be necessary.

For now, we have to create all the antimatter ourselves. Luckily, there is technology available to create antimatter through the use of high-energy particle colliders, also called "atom smashers."

Atom smashers, like CERN, are large tunnels lined with powerful supermagnets that circle around to propel atoms at near-light speeds. When an atom is sent through this accelerator, it slams into a target, creating particles. Some of these particles are antiparticles that are separated out by the magnetic field.

These high-energy particle accelerators only produce one or two picograms of antiprotons each year. A picogram is a trillionth of a gram. All of the antiprotons produced at CERN in one year would be enough to light a 100-watt electric light bulb for three seconds. It will take tons of antiprotons to travel to interstellar destinations.

NASA is possibly only a few decades away from developing an antimatter spacecraft that would cut fuel costs to a fraction of what they are today. In October 2000, NASA scientists announced early designs for an antimatter engine that could generate enormous thrust with only small amounts of antimatter fueling it. The amount of antimatter needed to supply the engine for a one-year trip to Mars could be as little as a millionth of a gram, according to a report in that month's issue of Journal of Propulsion and Power.

Matter-antimatter propulsion will be the most efficient propulsion ever developed because 100 percent of the mass of the matter and antimatter are converted into energy. When matter and antimatter collide, the energy released by their annihilation releases about 10 billion times the energy that chemical energy such as hydrogen and oxygen combustion, the kind used by the space shuttle, releases.

Matter-antimatter reactions are 1,000 times more powerful than the nuclear fission produced in nuclear power plants and 300 times more powerful than nuclear fusion energy. So matter-antimatter engines have the potential to take us farther with less fuel. The problem is creating and storing the antimatter. There are three main components to a matter-antimatter engine:

• Magnetic storage rings : Antimatter must remain separate from normal matter so storage rings with magnetic fields can move the antimatter around the ring until it is needed to create energy.
• Feed system : When the spacecraft needs more power, the antimatter will be released to collide with a target of matter, which releases energy.
• Magnetic rocket nozzle thruster : Like a particle collider on Earth, a long, magnetic nozzle will move the energy created by the matter-antimatter through a thruster.

Approximately 10 grams of antiprotons would be enough fuel to send a manned spacecraft to Mars in one month. Today, it takes a little less than a year for an unmanned spacecraft to reach Mars. In 1996, the Mars Global Surveyor took 11 months to arrive at Mars.

Scientists believe that the speed of a matter-antimatter powered spacecraft would allow man to go where no man has gone before in space. It would be possible to make trips to Jupiter and even beyond the heliopause, the point at which the sun 's radiation ends. But it will still be a long time before astronauts are asking their starship's helmsman to take them to warp speed.

This article was updated in conjunction with AI technology, then fact-checked and edited by a HowStuffWorks editor.

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AIR & SPACE MAGAZINE

Breakthrough in antimatter physics has some dreaming of starships.

The cost is still a problem, though.

Elizabeth Howell

Could antimatter engines power interstellar travel? Experts are divided after antimatter research took a large step forward today. Researchers publishing in the journal Nature have measured the spectrum of antihydrogen—the antimatter equivalent of hydrogen—for the first time, which should allow physicists to investigate more precisely how this exotic material differs from hydrogen. The ultimate goal is learning why antimatter is so scarce in the universe, when models suggest that the Big Bang should have produced equal amounts of matter and antimatter.

Co-author Jeffrey Hangst, a physics professor at Aarhus University, called the research at CERN a breakthrough. Six years ago, his consortium discovered how to trap a single atom of antihydrogen in a magnetic field; now they can trap 15 atoms simultaneously. Yet the painstaking trapping process has Hangst convinced that antimatter engines are impossible. Today it takes a huge accelerator to produce just a few atoms, nowhere near the amount needed for an antimatter-powered rocket.

“These people [who want to built antimatter engines] are wasting their time,” Hangst says. “It’s about making enough of it. It takes much more energy to produce than [the energy] you get out of it, and it will take longer than the age of the universe.”

The idea of interstellar travel got a huge boost this year when Russian billionaire Yuri Milner announced the Breakthrough Starshot Initiative . It aims to send a tiny probe (1 gram) to a nearby star within a generation, but initially is focusing on beamed energy propulsion rather than more exotic concepts like antimatter drive and fusion drive, neither of which are within the realm of current technology.

Physicist Steve Howe, a former staff scientist at the Los Alamos National Laboratory, has been considering antimatter engines since the 1980s. He identifies three problems that have to be solved before an interstellar vehicle could be built: producing antimatter in sufficient quantities, storing it, and converting it to propulsion. With enough money, Howe is convinced it’s feasible.

“A lot of people have used current cost estimates and current facilities to estimate the cost of producing large quantities [of antimatter],” he says. “That’s false. The facilities now aren’t geared to making antimatter in large quantities.”

Howe, founder and senior scientist at Hbar Technologies , received funding in 2002 for early research into antimatter propulsion through NASA’s Advanced Innovative Concepts program. Earlier this month, Hbar finished a successful Kickstarter campaign that raised $2,280 . The money will be used in part to design a production complex to produce several grams of antiprotons per year.

Howe acknowledges that antimatter production will be a hurdle. The U.S. Fermilab facility was able to produce just a nanogram (billionth of a gram) of antimatter per year before the production line was shut down in 2011. But those particles were specifically for high-energy experiments. “They extract one in a million that have the right energy to reaccelerate the particles up to high speed,” Howe says.

Capturing more generic particles, he says, would have increased antimatter production to a microgram (millionth of a gram) per year, or the equivalent energy of 20 kilograms of TNT. He estimates that research to develop magnetic field antimatter storage of the kind that would be needed for a spacecraft would take a few million dollars and roughly five years of research.

As for producing antimatter in enough quantity to power a starship, that will take much more time and money, according to Howe. Increasing production to even a milligram (thousandth of a gram) of antimatter (20 tons of TNT) per year would require a national-scale investment of billions of dollars, he says. To power one interstellar mission every decade, his group estimates a production rate of two grams per year will be needed.

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Elizabeth Howell | | READ MORE

Elizabeth Howell is a freelance space journalist in Ottawa, Canada. You can see her latest work at @howellspace.

• Q: Does anti-matter really move backward through time?

Physicist : The very short answer is: yes, but not in time-traveler-kind-of-way.

There is a “symmetry” in physics implied by our most fundamental understanding of physical law , and is never violated by any known process, that’s called the “ CPT symmetry “.  It says that if you take the universe and everything in it and flip the electrical charge (C), invert everything as though through a mirror (P), and reverse the direction of time (T), then the base laws of physics all continue to work the same.

Charge Conjugation Flip all the charges in the universe.  Most important for us, protons become negatively charged and electrons become positively charged.  Charge conjugation keeps all of the laws of electromagnetism unchanged.  Basically, after reversing all of the charges, likes are still likes (and repel) and opposites are still opposites (and attract).

Time Reversal If you watch a movie in reverse a lot of nearly impossible things happen.  Meals are uneaten, robots are unexploded, words are unsaid, and hearts are unbroken.  The big difference between the before and after in each situation is entropy , which almost always increases with time.  This is a “statistical law” which means that it only describes what “tends” to happen.  On scales-big-enough-to-be-seen entropy “doesn’t tend” to decrease in the sense that fire “doesn’t tend” to change ash into paper; it is a law as absolute as any other.  But on a very small scale entropy becomes more suggestion than law .  Interactions between individual particles play forward just as well as they play backwards, including particle creation and annihilation.

Left: An electron and a positron annihilate producing two photons. Right: Two photons interact creating an electron and a positron.  We see both of these events in nature routinely and they are literally time-reverses of each other.

Parity If you watch the world through a mirror, you’ll never notice anything amiss.  If you build a car, for example, and then build another that is the exact mirror opposite, then both cars will function just as well as the other.  It wasn’t until 1956 that we finally had an example of something that behaves differently from its mirror twin.  By putting ultra-cold radioactive cobalt-60 in a strong magnetic field the nuclei, and the decaying neutrons, were more or less aligned and we found that the electrons shot out ( β – radiation ) in one direction preferentially.

Chien-Shiung Wu in 1956 demonstrating how difficult it is to build something that behaves differently than its mirror image.

The way matter interacts through the weak force has handedness in the sense that you can genuinely tell the difference between left and right.  During β – (“beta minus”) decay a neutron turns into a proton while ejecting an electron, an anti-electron neutrino , and a photon or two (usually) out of the nucleus.  Neutrons have spin , so defining a “north” and “south” in analogy to the way Earth rotates, it turns out that the electron emitted during β – decay is always shot out of the neutron’s “south pole”.  But mirror images spin in the opposite direction (try it!) so their “north-south-ness” is flipped.  The mirror image of the way neutrons decay is impossible.  Just flat out never seen in nature.  Isn’t that weird?  There doesn’t have to be a “parity violation” in the universe, but there is.

Matter’s interaction with the weak force is “handed”.  When emitting beta radiation (a weak interaction) matter and anti-matter are mirrors of each other.

Parity and charge are how anti-matter is different from matter.  All anti-matter particles have the opposite charge of their matter counterparts and their parity is flipped in the sense that when anti-particles interact using the weak force, they do so like matter’s image in a mirror.  When an anti-neutron decays into an anti-proton, a positron, and an electron-neutrino, the positron pops out of its “north pole”.

CPT is why physicists will sometimes say crazy sounding things like “an anti-particle (CP) is like the normal particle traveling back in time (T)”.  In physics, whenever you’re trying to figure out how an anti-particle will behave in a situation you can always reverse time and consider how a normal particle traveling into the past would act.

“Anti-matter acts like matter traveling backward in time”. Technically true, but not in a way that’s useful or particularly enlightening for almost anyone to know.

This isn’t as useful an insight as it might seem.  Honestly, this is useful for understanding beta decay and neutrinos and the fundamental nature of reality or whatever, but as far as your own personal understanding of anti-matter and time, this is a remarkably useless fact.  The “backward in time thing” is a useful way of describing individual particle interactions, but as you look at larger and larger scales entropy starts to play a more important role, and the usual milestones of passing time (e.g., ticking clocks, fading ink, growing trees) show up for both matter and anti-matter in exactly the same way.  It would be a logical and sociological goldmine if anti-matter people living on an anti-matter world were all Benjamin Buttons , but at the end of the day if you had a friend made of anti-matter (never mind how), you’d age and experience time in exactly the same way.  You just wouldn’t want to hang out in the same place .

The most important, defining characteristic of time is entropy and entropy treats matter and anti-matter in exactly the same way; the future is the future is the future for everything.

10 Responses to Q: Does anti-matter really move backward through time?

What you say seems to suggest experiments to test it, but my guess is it’s not going to work, as the effect would have been observed already. “The most important, defining characteristic of time is entropy”. As you say, locally entropy doesn’t always apply, though over a larger area it does. Where you get order over a small area, shouldn’t time lose its directionality? could that be tested for? we could even contrive things to make increasing order in one place for short time. so shouldn’t time run backwards there? we do that a lot in fact, and time runs forwards, or we wouldn’t be able to do it. Or are you saying that the link between entropy and time is only a vague one?

The Hilbert Book Test Model is a pure mathematical model of the lower levels of the structure of physical reality. It base consists of an infinite dimensional separable Hilbert space and its unique non-separable companion Hilbert space. Both Hilbert spaces use members of a version of the quaternionic number system to deliver the values of their inner products. Thus also the eigenvalues of the operators that map Hilbert spaces onto themselves are quaternions. A special reference operator applies the rational members of the selected quaternionic number system to enumerate an orthonormal base of the separable Hilbert space. It uses the base vectors as its eigenvectors and the enumerators as the corresponding eigenvectors. The eigenspace can be used as a parameter space of a set of quaternionic functions and these functions can be used to define a category of defined operators that reuse the eigenvectors of the reference operator and apply the corresponding target values of thev function as its eigenvalues. The same trick can be performed in the non-separable companion Hilbert space, but this time all members of the number system are used. A scanning vane can be defined as a subspace of the separable Hilbert space that is spanned by the eigenvector of the selected reference operator that share the same real part of the corresponding eigenvalues. The real value can be interpreted as progression. The vane splits the Hilbert space in a historic part, a static status quo (the vane), and a future part. The non-separable Hilbert space can be considered to embed its separable companion. And the vane can be interpreted as representing the ongoing embedding process. This simple dynamic model offers two views. One is the creator’s view. The creator has access to all dynamic geometric data that are stored in the Hilbert spaces. The other view is the observer’s view. Observers are constituted from elementary modules that travel with the vane. In the vane, rays represent them. Rays are one-dimensional subspaces. In the vane, each elementary module owns a private location that is presented by the imaginary part of a quaternion. A stochastic mechanism generates these locations. Therefore, the elementary modules appear to hop around in a stochastic hopping path. After a while, the hop landing locations have formed a coherent location swarm. The swarm and the hopping path represent the elementary module. A location density distribution describes the coherent swarm. This distribution equals the squared modulus of the wave function of the elementary module. The observers have no access to the future part of the model. They get their information via information messengers that travel in the embedding continuum. The embedding continuum is the living space of the elementary modules. Thus, it is also the living space of all observers.

In the creator’s view the elementary modules live in a tube that zigzags through the living space. The tube may just cross the vane, but it may also happen that the tube reflects against the vane. The reflection can occur at the historic side of the vane, but it can also occur at the future side. With other words, the tube may cross the vane multiple times. This means that the same elementary module can exist multiple times at the same instant in the vane. These appearances are entangled in a way that must be mysterious to the observers. The observers will interpret the reflection against the historic side of the vane as the annihilation of a pair of an elementary module and its anti-module. The observers interpret the reflection against the future side of the vane as the creation of a pair of an elementary module and its anti-module.

The way I think of the ‘direction of time’ is that while the equations are symmetric under CPT the solutions need not be. It’s kind of like a ferro-magnet which has no preferred direction, but based on initial condiitions ends up pointing in only one direction.

If you start with a bunch of particles confined to the corner of a box, they will spread out and fill the box whether you run the clock forward or backward.

-Arthur Snyder, SLAC

I think that the violation of pt shows that the antiparticles travel backward in time,and the space is twisted in two opposed orientations:left handed and right handed in spacetime curves in the fourth dimension,explaining the constancy and the limit for the speed of light

Had an intriguing idea. As it has been found that thunderstorms create “clouds” of antimatter, perhaps ball lightning is in fact such a cloud moving back towards the storm that created it and then canceling out. In order for the books to balance energy must be conserved so the mysterious gamma ray flashes might be these events. It would also account for BL being observed before a storm, as the visible effects might be short lived. Don’t forget that antimatter could well have neutral or even negative effective gravitation so would tend to rise and air currents would do the rest.

Why momentum and position can’t remain in same time?

In reality the antiparticles run forward energy to win energy and appear as ele as elétrons running back in time,Then there infinities spacetime ,was to the particles and antiparticles each one with diferents métrics of spacetime,it is violating cp.do not exist antimatter in the universe.the antiparticles are symmetrics of the matter

But we all know that time(T) is scalar, It only has magnitude but no direction…. but here you said “reverse the direction of time (T)” in the para “There is a “symmetry” in physics implied by our most fundamental understanding of physical law, and is never violated by any known process, that’s called the “CPT symmetry“. It says that if you take the universe and everything in it and flip the electrical charge (C), invert everything as though through a mirror (P), and reverse the direction of time (T), then the base laws of physics all continue to work the same.”

It seems worth while to point out that while the equations of physics are the same under CPT, the solutions need not be. Hence the direction of time.

Beyond the scientific which are beyond me mostly , I’ve had on my book shelf right from 1968 ish two small SF paperbacks by Jack Williamson ” Seetee Ship ” & ” Seetee shock ” which always stayed bright in my imagination as really interesting concepts where there’s play on the idea of forward & backward movement in time around an alien Seetee ship etc . Re – reading them again after decades , now in 2022 – time has sadly seriously not treated them at all well in so many ways, from the reality of Venus through to anti matter it’s self. but – hell – they embody the hey-day of my love of SF ….

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• Q: What is the most complicated equation?
• Q: What is quantum immortality?
• Q: If you double your bet every time you lose, won’t you eventually win and come out ahead?
• Q: Will we ever discover a completely new color?
• Q: With entangled particles, can you tell when/how the other particle is measured?
• Q: How hard would it be to keep the Moon from drifting away?
• For the first time ever, you can buy a book!
• Q: Where is all the anti-matter?
• Q: Is it possible to write a big number using a small number? Is there a limit to how much information can be compressed?
• Q: Is reactionless propulsion possible?
• Q: How can I set up a random gift exchange that’s different from year to year?
• Q: How does “1+2+3+4+5+… = -1/12” make any sense?
• There’s something new under the Sun!
• Q: Is it more efficient to keep keep a swimming pool warm or let it get cold and heat it up again?
• Q: What determines the size of the bright spot when you focus sunlight with a lens?
• Q: Why are numerical methods necessary? If we can’t get exact solutions, then how do we know when our approximate solutions are any good?
• Burning Man 2017
• Q: How can something be “proven” in science or math?
• Q: If time is relative, then how can we talk about how old the universe is?
• Q: How can carbon dating work on things that were never alive?
• Teleportation! In space!
• Q: If the world is a giant magnet, how come we can’t build a repelling magnet that can float?
• Q: How can something have different amounts of energy from different points of view?
• Q: Where is the middle of nowhere?
• Q: If light is a wave, then what’s doing the waving?
• Q: If you’ve got different amounts of debt in different accounts with different interest rates, how should you pay them down?
• Q: Should we be worried about artificial intelligence? By “we” I mean humans.
• Q: Why haven’t we been able to see the spectra of anti-hydrogen until recently? Why is it so hard to study anti-matter?
• Q: Does quantum mechanics really say there are other “mes”? Where are they?
• Q: In base ten 1=0.999…, but what about in other bases? What about in base 1?
• Q: How many samples do you need to take to know how big a set is?
• Q: How do we know that everyone has a common anecestor? How do we know that someone alive today will someday be a common ancestor to everyone?
• Q: Are some colors of light impossible? Can any color of light be made?
• Q: Is there anything unique about our solar system?
• Q: What is dark energy?
• Q: What are “actual pictures” of atoms actually pictures of?
• Q: If you were shrunk to microscopic size would you be able to see normally? Would you be able to see microscopic things?
• Q: How does one attain an understanding of everything?
• Q: Can planes (sheets) be tied in knots in higher dimensions the way lines (strings) can be tied in knots in 3 dimensions?
• Gravity Waves!
• Q: Is it possible to parachute to Earth from orbit?
• Q: Why can’t we see the lunar landers from the Apollo missions with the Hubble (or any other) telescope?
• Q: How bad would it be if we accidentally made a black hole?
• Q: What if gravity acted like magnetism?
• Q: When you write a fraction with a prime denominator in decimal form it repeats every p-1 digits. Why?
• Q: If atoms are 99.99% space, what “kind” of space is it? Is it empty vacuum?
• Q: Is geocentrism really so wrong? Is the Sun being at the “center” (i.e. the Earth orbiting the Sun) just an arbitrary reference frame decision, and no more true than the Earth being at the center?
• Q: Is there such a thing as half a derivative?
• Q: Why is our Moon drifting away while Mars’ moons are falling?
• Q: Why do we (people) wave our arms when we fall? Is it for attention?
• Q: What is the state of matter in deep space?
• Q: Is there a scientific conspiracy?
• Q: After the heat death of the universe will anything ever happen again?
• Q: Why does kinetic energy increase as velocity squared?
• Q: Quaternions and Octonions: what?
• Q: Since the Earth is spinning and orbiting and whatnot, are we experiencing time wrong because of time dilation?
• Q: How do I know my windmill is on straight?
• Q: If all matter originated from a single point, does that mean all matter is entangled?
• Q: How good is the Enigma code system compared to today’s publicly available cryptography systems?
• Q: When “drawing straws” is it better to be first or last?
• Q: What would happen if there was a giant straw connecting the Earth’s atmosphere right above the ground to space?
• Q: Can a human being survive in the fourth dimension?
• Q: Why radians?
• Q: If the Sun pulls things directly toward it, then why does everything move in circles around it?
• Q: Why is the area of a circle equal to πR 2 ?
• 0.999… revisited
• Q: Before you open the box, isn’t Schrödinger’s cat alive or dead, not alive and dead?
• Q: How many times do you need to roll dice before you know they’re loaded?
• Q: Since it involves limits, is calculus always an approximation?
• Q: How does Earth’s magnetic field protect us?
• Q: If a long hot streak is less likely than a short hot streak, then doesn’t that mean that the chance of success drops the more successes there are?
• Q: Where do the rules for “significant figures” come from?
• Q: If time slows down when you travel at high speeds, then couldn’t you travel across the galaxy within your lifetime by just accelerating continuously?
• Q: When something falls on your foot, how much force is involved?
• Q: If nothing can escape a black hole’s gravity, then how does the gravity itself escape?
• Q: Is there a formula for finding primes? Do primes follow a pattern?
• Q: If the number of ancestors you have doubles with each generation going back, you quickly get to a number bigger than the population of Earth. Does that mean we’re all a little inbred?
• Q: Why are many galaxies, our solar system, and Saturn’s rings all flat?
• Q: How do you define the derivatives of the Heaviside, Sign, Absolute Value, and Delta functions? How do they relate to one another?
• Q: What does “E=mc 2 ” mean?
• Q: Is it possible to have a completely original thought?
• Q: How can the universe expand faster than the speed of light?
• Q: How fast are we moving through space? Has anyone calculated it?
• Q: If you flip a coin forever, are you guaranteed to eventually flip an equal number of heads and tails?
• Q: What is radioactivity and why is it sometimes dangerous?
• Q: How do we know that π never repeats? If we find enough digits, isn’t it possible that it will eventually start repeating?
• Q: Why does carbon dating detect when things were alive? How are the atoms in living things any different from the atoms in dead things?
• Q: What role does Dark Matter play in the behavior of things inside the solar system?
• Q: Are some number patterns more or less likely? Are some betting schemes better than others?
• Q: Why does iron kill stars?
• Q: According to relativity, things get more massive the faster they move. If something were moving fast enough, would it become a black hole?
• Q: How do we know that atomic clocks are accurate?
• Q: “i” had to be made up to solve the square root of negative one. But doesn’t something new need to be made up for the square root of i?
• Q: Could the tidal forces of the Sun and Moon be used to generate power directly?
• Q: What would it be like if another planet just barely missed colliding with the Earth?
• Q: What are “delayed choice experiments”? Can “wave function collapse” be used to send information?
• Q: Why can some creatures walk on water yet I (a human) can’t?
• Q: What fair dice can be simulated by adding up other dice?
• Q: How do I encrypt/hide/protect my email?
• Q: Where do the weird rules for rational numbers come from? (Dealing with fractions)
• Dragon*Con 2013
• Q: Why doesn’t the air “sit still” while the Earth turns under it?
• Q: Can resonance be used to destroy anything? Is the “brown note” possible?
• Q: Are there examples of quantum mechanics that can be seen in every-day life, or do they only show up in the lab?
• Q: Why does it take thousands of years for light to escape the Sun?
• Q: What does it mean for light to be stopped or stored?
• Q: What are quasi-particles? Why do phonons and photons have such similar names?
• The nuptial effect
• Q: How do you prove that the spacetime interval is always the same?
• Q: Are numbers real?
• Q: If time were reversed would things fall up?
• Q: Why don’t “cheats” ever work on the uncertainty principle? What’s uncertain in the uncertainty principle?
• Q: Do the past and future exist? If they do, is the future determined and what does that mean for quantum randomness?
• Basic math with infinity
• Q: What is the Planck length? What is its relevance?
• Q: What causes friction? (and some other friction questions)
• Q: Is fire a plasma? What is plasma?
• Q: Why are determinants defined the weird way they are?
• Q: Are white holes real?
• Q: If a photon doesn’t experience time, then how can it travel?
• Q: What is energy? What is “pure energy” like?
• Q: Why is Schrodinger’s cat both dead and alive? Is this not a paradox?
• Q: What kind of telescope would be needed to see a person on a planet in a different solar system?
• Q: Is Murphy’s law real?
• Q: Why doesn’t life and evolution violate the second law of thermodynamics? Don’t living things reverse entropy?
• Q: Does quantum mechanics really say that there’s some probability that objects will suddenly start moving or that things can suddenly “shift” to the other side of the universe?
• Q: Using modern technology, are we any closer to turning lead into gold than alchemists were hundreds of years ago?
• Q: How do you turn/change directions in space?
• Q: If a man hangs on an un-insulated wire using both his hands what will happen and why?
• Learning intro number theory
• Q: Is the Alcubierre warp drive really possible? How close are we to actually building one and going faster than light?
• Q: Is darkness a wave the way light is a wave? What is the speed of dark?
• Q: Is it a coincidence that a circles circumference is the derivative of its area, as well as the volume of a sphere being the antiderivative of its surface area? What is the explanation for this?
• Q: If hot air rises, why is it generally colder at higher elevations?
• Q: What is quantum teleportation? Why can’t we use it to communicate faster than light?
• Q: Since all particles display wave-like characteristics, does that imply that one could use destructive wave interference to destroy or at least drastically change a particle?
• Q: How does the Oberth Effect work, and where does the extra energy come from? Why is it better for a rocket to fire at the lowest point in its orbit?
• Q: How do lenses that concentrate light not violate the second law of thermodynamics? If you use a magnifying glass to burn ants, aren’t you making a point hotter than the ambient temperature without losing energy?
• Q: What makes natural logarithms natural? What’s so special about the number e?
• Q: If the world were to stop spinning, would the people and everything on it be considered ‘lighter’ or ‘heavier’? Would any change take place? And does centrifugal force have an effect on gravity?
• Q: Two entangled particles approach a black hole, one falls in and the other escapes. Do they remain entangled? What about after the black hole evaporates?
• Q: If there are 10 dimensions, then why don’t we notice them?
• Q: Will the world end tomorrow?
• Q: In an infinite universe, does everything that’s possible have to happen somewhere?
• Q: Which of Earth’s life forms could survive on each planet of the Solar System?
• Q: What are fractional dimensions? Can space have a fractional dimension?
• Q: Are shadows 2-dimensional? Are there any real examples of 2-dimensional things in the universe?
• Q: Is it possible to experience different rates of time? If time were to speed up, slow down, or stop, what would you experience?
• Q: How many theorems are there?
• Q: How much of a direct effect do planets and stars have on us? Is astrology reasonable or plausable?
• Q: Why are scientists looking for life in space by looking for water? How can they be sure that all life uses water?
• Q: If energy is neither created nor destroyed, what happens to the energy within our bodies and brains when we die?
• Q: Could Kurt Vonnegut’s “Ice-9 catastrophe” happen?
• Q: How accurately do we need to know π? Is there a reason to know it out to billions of digits?
• My bad: If fusion in the Sun suddenly stopped, what would happen?
• Q: If fusion in the Sun suddenly stopped, what would happen?
• Q: Does opening a refrigerator cool down the room?
• Q: What is the probability of an outcome after it’s already happened?
• Q: How do you answer a question scientifically?
• Q: Why are the days still longer than nights, until a few days after the fall equinox?
• Q: What is a Fourier transform? What is it used for?
• Q: What are singularities? Do they exist in nature?
• Q: Is it likely that there are atoms in my body that have traveled from the other side of the planet, solar system, galaxy, or universe?
• Q: Is there a number set that is “above” complex numbers?
• Q: Are the brain and consciousness quantum mechanical in nature?
• Q: How are voltage and current related to battery life? What is the difference between batteries with the same voltage, but different shapes or sizes? What about capacitors?
• Q: What are virtual particles?
• Q: Would it be possible to create an antimatter weapon by “harvesting” enough antimatter, containing it in an electro-magnetic field and placing that in a projectile?
• Q: If Earth was flat, would there be a horizon? If so, what would it look like? If the Earth was flat and had infinite area, would that change the answer?
• Q: Is there an experiment which could provide conclusive evidence for either the Many Worlds or Copenhagen interpretations of quantum physics?
• Q: If you could drill a tunnel through the whole planet and then jumped down this tunnel, how would you fall?
• Q: How many people riding bicycle generators would be needed, in an 8-hour working day, to equal or surpass the energy generated by an average nuclear power plant?
• Q: Why is hitting water from a great height like hitting concrete?
• Q: How does instantaneous communication violate causality?
• Q: What is the “False Vacuum” and are we living in it?
• Q: How would the universe be different if π = 3?
• Q: Is it possible for an artificial black hole to be created, or something that has the same effects? If so, how small could it be made?
• Q: Do colors exist?
• Q: How can we see the early universe and the Big Bang? Shouldn’t the light have already passed us?
• Q: Are beautiful, elegant or simple equations more likely to be true?
• Q: If quantum mechanics says everything is random, then how can it also be the most accurate theory ever?
• Q: Why do wet stones look darker, more colorful, and polished?
• Q: What would the universe be like with additional temporal dimensions?
• The 2012 Venus transit
• Q: Why haven’t we discovered Earth-like planets yet?
• Q: Is quantum randomness ever large enough to be noticed?
• Q: How is radiometric dating reliable? Why is it that one random thing is unpredictable, but many random things together are predictable?
• Q: Is the final step in evolution an ascension into an energy-based lifeform?
• Q: What would life be like in higher dimensions?
• Q: How much does fire weigh?
• Q: Since the real-world does all kinds of crazy calculations in no time, can we use physics to calculate stuff?
• Q: Is there some way to actually play quidditch?
• Q: Can you poke something that’s far away with a stick faster than it would take light to get there?
• Q: Does how you deal cards affect how random they are?
• Q: Will CERN awaken the Elder Gods?
• Q: The information contained in a big system isn’t the same as the amount of information in its parts. Why?
• Q: Is the quantum zeno effect a real thing?
• Q: Is there an intuitive proof for the chain rule?
• Q: How do you write algorithms to enycrypt things?
• Q: Satellites experience less time because they’re moving fast, but more time because they’re so high. Is there an orbit where the effects cancel out? Is that useful?
• Q: Is it possible to objectively quantify the amount of information a sentence contains?
• Q: What would happen if a black hole passed through our solar system?
• Q: If you are talking to a distant alien, how would you tell them which way is left and which way is right?
• Q: Would it be possible in the distant future to directly convert matter into energy?
• Q: What’s the difference between anti-matter and negative-matter?
• Q: Why does gravity make some things orbit and some things fall?
• Q: Do you need faith to believe in science?
• Q: What keeps spinning tops upright?
• Q: Do time and distance exist in a completely empty universe?
• Q: Why is it that photographs of wire mesh things, like window screens and grates, have waves in them?
• Q: How does quantum physics affect electron configurations and spectral lines?
• Q: Is it possible for an atomic orbital to exist beyond the s, p, f and d orbitals they taught about in school? Like could there be a (other letter) orbital beyond that?
• Q: Will the world end in 2012?
• Q: How do you find the height of a rocket using trigonometry?
• Q: What are chaos and chaos theory? How can you talk about chaos?
• Q: What is the Riemann Hypothesis? Why is it so important?
• Q: Why does the entropy of the universe always increase, and what is the heat death of the universe?
• Q: Could God have existed forever? Is it actually feasibly possibly for some ‘being’ to have just existed, infinitely?
• Q: How can wormholes be used for time travel?
• Q: If gravity suddenly increased would airplanes fall out of the sky, or would it compress the air in such a way that airplanes could keep flying?
• Entanglement omnibus!
• Q: How are imaginary exponents defined?
• Q: Why do nuclear weapons cause EMPs (electromagnetic pulses)?
• Q: How does the expansion of space affect the things that inhabit that space? Are atoms, people, stars, and everything else getting bigger too?
• Q: What would Earth be like if it didn’t turn?
• Q: According to the Many Worlds Interpretation, every event creates new universes. Where does the energy and matter for the new universes come from?
• Q: Can wind chill make things “feel” colder than absolute zero?
• Q: What is “spin” in particle physics? Why is it different from just ordinary rotation?
• Q: What is Bayes’ rule and how do I use it to improve my life?
• Q: Are there universal truths?
• Q: What’s the difference between black holes and worm holes? Could black holes take you to other universes?
• Q: Is there an equation that determines whether a question gets answered on ask a mathematician/physicist?
• Q: If you could hear through space as though it were filled with air, what would you hear?
• Q: What is the three body problem?
• Q: How are fractals made?
• Q: CERN’s faster than light neutrino thing: WTF?
• Q: What’s the point of purely theoretical research?
• Q: Why does lightning flash, but thunder rolls?
• Q: Hyperspace, warp drives, and faster than light travel: why not?
• Burning Man 2011
• Q: If light slows down in different materials, then how can it be a universal speed?
• Q: What is mass?
• Q: How much of physics can be deduced from previous equations/axioms?
• Q: If God were all-seeing and all-knowing, the double-slit experiment wouldn’t work, would it? Wouldn’t God’s observation of the location of the photon collapse its probability wave function?
• Q: How do those “executive ball clicker” things work?
• Q: Why is cold fusion so difficult?
• Q: Why does light choose the “path of least time”?
• Q: Does light experience time?
• Q: Would it be possible for humans to terraform mars?
• Q: Can light be used to transfer energy instead of power lines?
• Particle physics, neutrinos, and chirality too!
• Q: What are integral transforms and how do they work?
• Q: How does reflection work?
• Q: What does a measurement in quantum mechanics do?
• Q: If you stood in the beam of a particle accelerator, what would happen?
• Q: What exactly is the vacuum catastrophe and what effects does this have upon our understanding of the universe?
• Q: What is a “measurement” in quantum mechanics?
• Q: How close is Jupiter to being a star? What would happen to us if it were?
• Q: Can you fix the “1/0 problem” by defining 1/0 as a new number?
• Q: How can we have any idea what a 4D hypercube or any n-D object “looks like”? What is the process of developing a picture of a higher dimensional object?
• Q: Is it possible to destroy a black hole?
• Q: Why does the Earth orbit the Sun?
• Q: If you suddenly replaced all the water drops in a rainbow with same-sized spheres of polished diamond, what would happen to the rainbow? How do you calculate the size of a rainbow?
• Q: If we meet aliens, will they have the same math and physics that we do?
• Q: Is 0.9999… repeating really equal to 1?
• Q: What would Earth be like to us if it were a cube instead of spherical? Is this even possible?
• Q: How do velocities add? If I’m riding a beam of light and I throw a ball, why doesn’t the ball go faster than light?
• Q: What is the universe expanding into? What’s outside the universe?
• Cheap experiments and demonstrations for kids.
• Q: How do I estimate the probability that God exists?
• Q: How do you calculate 6/2(1+2) or 48/2(9+3)? What’s the deal with this orders of operation business?
• Q: Is there a single equation that proves black holes are real?
• Q: Is the edge of a circle with an infinite radius curved or straight?
• Q: As a consequence of relativity, objects becomes more massive when they’re moving fast. What is it about matter that causes that to happen?
• Q: What is the evidence for the Big Bang?
• Q: Is there a formula to find the Nth term in the Fibonacci sequence?
• Q: Why is the integral/antiderivative the area under a function?
• Mathematical proof of the existence of God.
• Video: Getting Computers to Learn
• Q: What is going on in a nuclear reactor, and what happens during a meltdown?
• Q: How do I find the love of my life? (a Mathematician’s perspective)
• Q: Are all atoms radioactive?
• Q: How do you talk about the size of infinity? How can one infinity be bigger than another?
• Q: Why does E=MC 2 ?
• Q: What are the equations of electromagnetism? What all do they describe to us?
• Q: What is the entropy of nothing?
• Q: How can quantum computers break encryption?
• Q: How does quantum computing work?
• Q: What causes buoyancy?
• My bad: If atoms are mostly made up of empty space, why do things feel solid?
• Q: How many mathematicians/physicists does it take to screw in a light bulb?
• Q: Why is it that (if you exclude 2 & 3) the difference between the squares of any two prime numbers is divisible by 12?
• Q: Why does relativistic length contraction (Lorentz contraction) happen?
• Q: Why does Lorentz contraction only act in the direction of motion?
• Q: If atoms are mostly made up of empty space, why do things feel solid?
• Q: Can we build a planet?
• Q: How does a scientist turn ideas into math?
• Q: Is Santa real?
• Q: Why isn’t the shortest day of the year also the day with the earliest sunset?
• Q: Why does “curved space-time” cause gravity?: A better answer.
• Q: According to relativity, two moving observers always see the other moving through time slower. Isn’t that a contradiction? Doesn’t one have to be faster?
• Q: What does 0^0 (zero raised to the zeroth power) equal? Why do mathematicians and high school teachers disagree?
• Q: Can you do the double slit experiment with a cat cannon?
• Q: How is the “Weak nuclear force” a force? What does it do?
• Q: Does Gödel’s Incompleteness Theorem imply that it’s impossible to be logical?
• Q: If accelerating charges radiate, and everything is full of charges, then why don’t I radiate every time I move?
• Q: If you zoom in far enough, what do particles look like?
• Q: What would you experience if you were going the speed of light?
• Q: Why is pi not a definite number?
• Q: What came before the big bang?
• Q: How do “Numerology Math Tricks” work? (adding digits and tricks with nines)
• Q: What is a magnetic field?
• Q: What is the probability that two randomly chosen people will have been born on the same day?
• Q: Which is a better approach to quantum mechanics: Copenhagen or Many Worlds?
• Q: Why is our vision blurred underwater?
• Q: In the NEC “faster than light” experiment, did they really make something go faster than light?
• Q: How does a Tesla coil work?
• Q: What are Feynman diagrams, how are they used (theoretically & practically), and are there alternative/competing diagrams to Feynman’s?
• Q: Does the 2nd law of thermodynamics imply that everything must eventually die, regardless of the ultimate fate of the universe?
• Q: What is The Golden Ratio? How is it used in Mathematics?
• Q: Why can’t you have an atom made entirely out of neutrons?
• Q: What is the physical meaning of “symmetries”? Why is there one-to-one correspondence between laws of conservation and symmetries? Why is it important that there is such correspondence?
• Q: Why does energy have to be positive (and real)?
• Q: How does the Twin Paradox work?
• Q: How can photons have energy and momentum, but no mass?
• Q: If you were on the inside of the Sun falling in, the matter closer to the surface doesn’t affect your acceleration, but the matter closer to the core does. Why is that?
• Q: How do surge protectors work?
• Relativity and Quantum Mechanics: the elevator pitch
• Q: Why are orbits elliptical? Why is the Sun in one focus, and what’s in the other?
• Q: What would happen if everyone in the world jumped at the same time?
• Q: How can electrons “jump” between places without covering the intervening distance?
• Q: Why do we only see one rainbow at a time?
• Q: Why does putting spin on a ball change how it moves through the air?
• Quantum mech, choices, and time travel too!
• Q: Why is the speed of light finite?
• Q: Why is the speed of light the fastest speed? Why is light so special?
• Q: Will we ever overcome the Heisenberg uncertainty principle?
• Q: If gravity is the reaction matter has on space, in that it warps space, why do physicist’s look for a gravity particle? Wouldn’t gravity be just a bi-product of what matter does to space?
• Q: Is it possible to beat the laws of physics?
• Q: What’s the chance of getting a run of K or more successes (heads) in a row in N Bernoulli trials (coin flips)? Why use approximations when the exact answer is known?
• Q: Aren’t physicists just doing experiments to confirm their theories? Couldn’t they “prove” anything they want?
• Q: What’s up with that “bowling ball creates a dip in a sheet” analogy of spacetime? Isn’t it gravity that makes the dip in the first place?
• Q: If we find a “Theory of Everything” will we be done?
• Q: Is it possible to say if the Earth is moving or sitting still without going into space?
• Q: Will there always be things that will not or cannot be known?
• Q: If you could see through the Earth, how big would Australia look from the other side?
• Q: How is it that Bell’s Theorem proves that there are no “hidden variables” in quantum mechanics? How do we know that God really does play dice with the universe?
• Q: Does an electric field have mass? Does it take energy to move an electric field?
• Q: What would the consequenses for our universe be if the speed of light was only about one hundred miles per hour?
• Q: Do virtual particles violate the laws that energy can be created or destroyed? Have virtual particles ever been observed? In any other instance can energy ever be destroyed or created?
• Video: How do we know that 1+1=2? A journey into the foundations of math.
• Q: Would it be possible to generate power from artificial lightning?
• Q: What is the optimum spectrum to visualize things with? Theoretically, which type of vision would be the best to see things with?
• Q: What causes iron, nickel, and cobalt to be attracted to magnets, but not other metals?
• Q: Is it possible to fill a black hole? If you were to continuously throw galaxies worth of matter into a black hole, would it ever fill up? And what would theoretically happen if all the matter in the universe was thrown into a single black hole?
• Q: Can math and science make you better at gambling?
• Q: Spectroscopy?
• Q: Is it possible to breach the center of a nebula?
• Q: How does a gravitational sling shot actually speed things up?
• Q: If energy is quantized, what is the least amount of energy possible? And how did they measure it?
• Q: How did Lord Kelvin come up with the absolute temperature? I mean, how could he say surely that it was 273.15 C below zero?
• Q: What do complex numbers really mean or represent?
• Q: Is it odd that the universe’s constants are all so perfectly conducive to life?
• Q: How/when will the world end?
• Q: What would happen if an unstoppable force met with an unmovable, impenetrable object?
• My bad: Have aliens ever visited Earth?
• Q: How do Bell pairs (entangled particles) behave experimentally?
• Video: What your Spiritual Guru Never Told you about Quantum Mechanics
• Q: How big does an object have to be to gravitationally attract a Human or have a molten core?
• Video: The Scientific Investigation of Aliens – Evidence Examined
• Q: How do I count the number of ways of picking/choosing/taking k items from a list/group/set of n items when order does/doesn’t matter?
• Q: Who would win in a fight: Gödel or Feynman?
• Q: How hard would it be to make a list of products of primes that could beat public key encryption?
• Q: What are complex numbers used for?
• Q: Can one truly create something from nothing? If matter formed from energy (as in the Big Bang expansion), where did the energy come from?
• Q: Why does wind make you colder, but re-entry makes you hotter?
• Q: Are explosions more or less powerful in space?
• Q: What is infinity? (A brief introduction to infinite sets, infinite limits, and infinite numbers)
• Q: Are there physical limits in the universe other than the speed of light?
• Q: Is it of any coincidence that mathematics is able to describe physical reality – given that both are inventions of the human mind?
• Q: If you were to break down an average human body into its individual atoms, and then laid the atoms out in a single straight line, how far would it stretch?
• Q: What’s it like when you travel at the speed of light?
• Q: Is there a real life example where two negatives make a positive?
• Q: Do the “laws” of physics and math exist? If so, where? Are they discovered or invented/created by humans?
• Q: Do we have free will?
• Q: How did mathematicians calculate trig functions and numbers like pi before calculators?
• Q: How can planes fly upside-down?
• Q: A flurry of blackhole questions!
• Q: Why does going fast or being lower make time slow down?
• Q: What’s so special about the Gaussian distribution (i.e. the normal distribution / bell curve)??
• Q: Is the universe infinitely old?
• Q: Have aliens ever visited Earth?
• Q: Why is the sky blue?
• Q: Is there a formula for how much water will splash, most importantly how high, and in what direction from the toilet bowl when you *ehem* take a dump in it ?
• Q: What is the meaning of the term “random”? Can thinking affect the future?
• Q: Is it possible to choose an item from an infinite set of items such that each one has an equal chance of being selected?
• Q: Do aliens exist?
• Q: Is it true that all matter is simply condensed energy?
• Q: Which is better: Math or Physics?
• Q: Why is the number 1 not considered a prime number?
• Q: If the universe is expanding and all the galaxies are moving away from one another, how is it possible for galaxies to collide?
• Q: What happens when you fall into a blackhole?
• Q: Is the total complexity of the universe growing, shrinking or staying the same?
• Q: If two trains move towards each other at certain velocities, and a fly flies between them at a certain constant speed, how much distance will the fly cover before they crash?
• Q: Why does oxygen necessarily indicate the presence of life?
• Q: What’s the relationship between entropy in the information-theory sense and the thermodynamics sense?
• Q: Would it be possible to kill ALL of Earth’s life with nuclear bombs?
• Q: Will black holes ever release their energy and will we be able to tell what had gone into them?
• Q: What are the Intersecting Chord and Power of a Point Theorems?
• Q: How far away is the edge of the universe?
• Q: Why do superconductors have to be cold?
• Q: Why does the leading digit 1 appear more often than other digits in all sorts of numbers? What’s the deal with Benford’s Law?
• Q: How does the Monty Hall Problem work?
• Q: How/Why are Quantum Mechanics and Relativity incompatible?
• Q: What the heck are imaginary numbers, how are they useful, and do they really exist?
• Q: What’s that third hole in electrical outlets for?
• Q: Do physicists really believe in true randomness?
• Q: Could a simple cup of coffee be heated by a hand held device designed to not only mix but heat the water through friction, and is that more efficient than heating on a stove and then mixing?
• Q: What did Einstein mean by: “Do not worry about your difficulties in Mathematics. I can assure you mine are still greater.”
• Q: Why does saliva boil in the vacuum of space?
• Q: Can things really be in two places at the same time?
• Q: Why do weird things happen so much?
• Q: Will CERN create a black hole?
• Q: What’s the highest population growth rate that the Earth can support?
• Q: What is time?
• Q: What is “Dark Matter”?
• Q: Why do heavy objects bend space and what is it they are bending?
• Q: Why does math work so well at modeling the world around us?
• Q: Why is it that when you multiply a positive number with a negative number you get a negative number?
• Q: What is the best way to understand relativity theory? Why is it so counter intuitive?
• Q: Will we ever go faster than light?
• Q: If you were on a space station, would you be able to tell the difference between centrifugal force and normal gravity?
• Q: Is teleportation possible?
• Q: If black holes are “rips” in the fabric of our universe, does it mean they lead to other universes? If so, then did time begin in that universe at the inception of the black hole? Could we be in a black hole?
• Q: Since pi is infinite, do its digits contain all finite sequences of numbers?
• Q: What is the connection between quantum physics and consciousness?
• Q: What is the probability that in a group of 31 people, none of them have birthdays in February or August?
• Q: What is the meaning of life?
• Q: Why is e to the i pi equal to -1?
• Q: How does a refrigerator work?
• Q: How do I find the love of my life?
• Q: Why does “curved space-time” cause gravity?
• Q: What is monotony?
• Q: How do we know if science is right?
• Q: How plausible is it that the laws of physics may actually function differently in other parts of the universe?
• Q: Are there an infinite number of prime numbers?
• Q: How can we prove that 2+2 always equals 4?

arXiv:physics/9812021v2 [physics.gen-ph] 20 Mar 1999

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Nasa’s fermi catches thunderstorms hurling antimatter into space.

Francis Reddy

Scientists using NASA’s Fermi Gamma-ray Space Telescope have detected beams of antimatter produced above thunderstorms on Earth, a phenomenon never seen before.

Scientists think the antimatter particles were formed in a terrestrial gamma-ray flash (TGF), a brief burst produced inside thunderstorms and shown to be associated with lightning. It is estimated that about 500 TGFs occur daily worldwide, but most go undetected.

“These signals are the first direct evidence that thunderstorms make antimatter particle beams,” said Michael Briggs, a member of Fermi’s Gamma-ray Burst Monitor (GBM) team at the University of Alabama in Huntsville (UAH). He presented the findings Monday, during a news briefing at the American Astronomical Society meeting in Seattle.

Fermi is designed to monitor gamma rays, the highest energy form of light. When antimatter striking Fermi collides with a particle of normal matter, both particles immediately are annihilated and transformed into gamma rays. The GBM has detected gamma rays with energies of 511,000 electron volts, a signal indicating an electron has met its antimatter counterpart, a positron.

Although Fermi’s GBM is designed to observe high-energy events in the universe, it’s also providing valuable insights into this strange phenomenon. The GBM constantly monitors the entire celestial sky above and the Earth below. The GBM team has identified 130 TGFs since Fermi’s launch in 2008.

“In orbit for less than three years, the Fermi mission has proven to be an amazing tool to probe the universe. Now we learn that it can discover mysteries much, much closer to home,” said Ilana Harrus, Fermi program scientist at NASA Headquarters in Washington.

The spacecraft was located immediately above a thunderstorm for most of the observed TGFs, but in four cases, storms were far from Fermi. In addition, lightning-generated radio signals detected by a global monitoring network indicated the only lightning at the time was hundreds or more miles away. During one TGF, which occurred on Dec. 14, 2009, Fermi was located over Egypt. But the active storm was in Zambia, some 2,800 miles to the south. The distant storm was below Fermi’s horizon, so any gamma rays it produced could not have been detected.

“Even though Fermi couldn’t see the storm, the spacecraft nevertheless was magnetically connected to it,” said Joseph Dwyer at the Florida Institute of Technology in Melbourne, Fla. “The TGF produced high-speed electrons and positrons, which then rode up Earth’s magnetic field to strike the spacecraft.”

The beam continued past Fermi, reached a location, known as a mirror point, where its motion was reversed, and then hit the spacecraft a second time just 23 milliseconds later. Each time, positrons in the beam collided with electrons in the spacecraft. The particles annihilated each other, emitting gamma rays detected by Fermi’s GBM.

Scientists long have suspected TGFs arise from the strong electric fields near the tops of thunderstorms. Under the right conditions, they say, the field becomes strong enough that it drives an upward avalanche of electrons. Reaching speeds nearly as fast as light, the high-energy electrons give off gamma rays when they’re deflected by air molecules. Normally, these gamma rays are detected as a TGF.

But the cascading electrons produce so many gamma rays that they blast electrons and positrons clear out of the atmosphere. This happens when the gamma-ray energy transforms into a pair of particles: an electron and a positron. It’s these particles that reach Fermi’s orbit.

The detection of positrons shows many high-energy particles are being ejected from the atmosphere. In fact, scientists now think that all TGFs emit electron/positron beams. A paper on the findings has been accepted for publication in Geophysical Research Letters.

“The Fermi results put us a step closer to understanding how TGFs work,” said Steven Cummer at Duke University. “We still have to figure out what is special about these storms and the precise role lightning plays in the process.”

NASA’s Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership. It is managed by NASA’s Goddard Space Flight Center in Greenbelt, Md. It was developed in collaboration with the U.S. Department of Energy, with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.

The GBM Instrument Operations Center is located at the National Space Science Technology Center in Huntsville, Ala. The team includes a collaboration of scientists from UAH, NASA’s Marshall Space Flight Center in Huntsville, the Max Planck Institute for Extraterrestrial Physics in Germany and other institutions.

By Francis Reddy NASA’s Goddard Space Flight Center , Greenbelt, Md.

The Large Hadron Collider reveals how far antimatter can travel through the Milky Way

The antimatter counterparts of light atomic nuclei can travel vast distances through the Milky Way before being absorbed, new findings have revealed.

As these particles travel, they potentially act as "messengers" for dark matter, so the revelation could help astronomers in the hunt for dark matter , the mysterious substance that accounts for around 85% of the universe's total mass but remains invisible because it doesn't interact with light.

Scientists at the ALICE collaboration arrived at the finding using antihelium nuclei, the antimatter equivalent of helium nuclei, created by collisions of heavy atomic nuclei at the Large Hadron Collider (LHC).

"Our results show, for the first time on the basis of a direct absorption measurement, that antihelium-3 nuclei coming from as far as the center of our galaxy can reach near-Earth locations," ALICE physics coordinator Andrea Dainese, said in a statement .

Related : 10 cosmic mysteries the Large Hadron Collider could unravel

Although this form of antimatter can be created in particle accelerators like the LHC, there are no natural sources of antimatter nuclei or "antinuclei" on Earth . However, these anti-particles are produced naturally elsewhere in the Milky Way , with scientists favoring two possible origins. 

The first suggested source for antinuclei is the interaction between high-energy cosmic radiation, which originates from outside the solar system , with atoms in the so-called interstellar medium that fills space between stars.

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The other suggested source of antinuclei is the annihilation of dark matter particles that are spread throughout the galaxy . While scientists know little about dark matter, they are certain that it is not comprised of particles like protons and neutrons that make up the everyday matter that forms stars, planets and us. Scientists believe dark matter, in contrast, is comprised of a wide range of particles with colorful names like WIMPs (weakly interacting massive particles) and MACHOs (massive compact halo objects). One scenario suggests that when dark matter particles collide, they annihilate into particles that then decay into light matter and antimatter particles, like electrons and their antimatter counterpart, positrons. If dark matter annihilation is indeed a source of antimatter in the universe, antimatter could point the way to dark matter, scientists hope.

Calculating the flux 

The quest to learn more about dark matter has prompted the development of space-based missions such as the Alpha Magnetic Spectrometer (AMS) aboard the International Space Station (ISS). AMS was designed at CERN, the home of the LHC, to search the cosmos for light antimatter nuclei that could indicate the presence the mysterious dark matter. 

But in order to determine whether dark matter is the source of antinucleons, scientists operating AMS and similar experiments first need to know how much light antimatter can pass through the Milky Way to reach their near-Earth locations, also known as the antiparticles' "flux." 

This flux is dependent on several factors, including the antimatter source, the rate at which it produces antinuclei, and the rate at which the antinuclei disappear as they journey from the center of our galaxy to Earth. This disappearance occurs when antimatter particles meet particles of traditional matter; either both are annihilated or the antimatter is absorbed by the matter.

The ALICE Collaboration investigated the disappearance of antimatter by using the LHC to collide lead atoms that have been ionized, or stripped of electrons. The physicists then measured how antihelium-3 nuclei created by these collisions interact with normal matter in the form of the ALICE detector. The experiment revealed for the first time the rate at which antihelium-3 nuclei disappear as they encounter ordinary matter. 

Using a computer program, the researchers then simulated the propagation of antiparticles through the galaxy and introduced to this model the disappearance rate measured at ALICE. This model allowed the researchers to extrapolate their results to the galaxy as a whole, and to look at the two suggested mechanisms of antinuclei production: One model assumed the antimatter came from cosmic-ray collisions with the interstellar medium, and the other model attributed antimatter to a hypothetical form of dark matter called weakly interacting massive particles (WIMPs).

For each of these mechanisms, the ALICE team estimated the transparency of the Milky Way to antihelium-3 nuclei — in other words, the distance antihelium-3 nuclei are free to travel before being destroyed or absorbed. The models revealed a transparency of around 50% in the dark matter model and a transparency ranging from 25% to 90% in the cosmic ray collision model, depending on the energy of the antinuclei created.

These values show that antihelium-3 nuclei originating from either process can travel long distances — up to several kiloparsecs, with each kiloparsec equivalent to around 3,300 light-years. (The Milky Way is about 30 kiloparsecs wide, according to NASA .)

— How the antimatter-hunting Alpha Magnetic Spectrometer works (infographic) — How much of the universe is dark matter? — Stars made of antimatter could exist in the Milky Way  

The results could be important in future experiments that count how many antinuclei arrive around Earth and with what energies in hopes of determining whether the origin of these antiparticles is cosmic-ray collisions or dark matter annihilation. 

"Our findings demonstrate that searches for light antimatter nuclei from outer space remain a powerful way to hunt for dark matter," ALICE spokesperson Luciano Musa said in the same statement.

The research is described in a paper published Monday (Dec. 12) in the journal Nature Physics .

Follow us on Twitter @Spacedotcom or on Facebook .

Join our Space Forums to keep talking space on the latest missions, night sky and more! And if you have a news tip, correction or comment, let us know at: [email protected].

Robert Lea is a science journalist in the U.K. whose articles have been published in Physics World, New Scientist, Astronomy Magazine, All About Space, Newsweek and ZME Science. He also writes about science communication for Elsevier and the European Journal of Physics. Rob holds a bachelor of science degree in physics and astronomy from the U.K.’s Open University. Follow him on Twitter @sciencef1rst.

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• rod "The first suggested source for antinuclei is the interaction between high-energy cosmic radiation, which originates from outside the solar system, with atoms in the so-called interstellar medium that fills space between stars. The other suggested source of antinuclei is the annihilation of dark matter particles that are spread throughout the galaxy. While scientists know little about dark matter, they are certain that it is not comprised of particles like protons and neutrons that make up the everyday matter that forms stars, planets and us. Scientists believe dark matter, in contrast, is comprised of a wide range of particles with colorful names like WIMPs (weakly interacting massive particles) and MACHOs (massive compact halo objects). One scenario suggests that when dark matter particles collide, they annihilate into particles that then decay into light matter and antimatter particles, like electrons and their antimatter counterpart, positrons. If dark matter annihilation is indeed a source of antimatter in the universe, antimatter could point the way to dark matter, scientists hope." So, is DM confirmed in this report as to DM being a WIMP or MACHO? The paper, Measurement of anti-3He nuclei absorption in matter and impact on their propagation in the Galaxy | Nature Physics States, "Propagation modellingThe possible sources of antinuclei in our Galaxy are either cosmic-ray interactions with nuclei in the interstellar gas or more exotic sources such as DM annihilations or decays. Cosmic rays mainly consist of protons and originate from supernovae remnants, whereas DM has so far escaped direct or indirect detection but its density profile can be modelled88."...Although coalescence-based models can successfully describe antinuclei production, the model uncertainties are still relatively large, which leads to substantial changes in the magnitude of antinuclei fluxes22,30,61." Apparently, DM is not nailed down yet as to exactly what it is. Reply
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"The last level of metaphor in the Alice books [ Alice in Wonderland , Through the Looking Glass ] is this: that life, viewed rationally and without illusion, appears be be a nonsense tale told by an idiot mathematician. At the heart of things, science finds only a mad never-ending quadrille of Mock Turtle Waves and Gryphon particles. For a moment the waves and particles dance in grotesque, inconceivably complex patterns capable of reflecting their own absurdity. We all live slapstick lives ..." -- Martin Gardner, The Annotated Alice .

"The universe is a practical joke of the general at the expense of the particular." -- Aleister Crowley, The Book of Lies .

The Discovery of Antimatter

In 1932 there were three known "elementary particles:"

Then Carl Anderson discovered a new one. He was working with a cloud chamber, a forerunner to a bubble chamber.

We will illustrate Anderson's discovery by considering some bubble chamber interactions. The bubble chamber is essentially a "tub" of superheated liquid hydrogen. The hydrogen is not only the detector, but its protons form a target for an incoming beam of particles. When a charged object goes through the superheated hydrogen, it leaves behind a track of bubbles; for a cloud chamber, such as used by Anderson, the track of a charged particle similarly leaves behind a string of cloud droplets. In the bubble chamber experiments below, the proton targets of the hydrogen are being bombarded with a beam of high energy negatively charge pi mesons ; these objects were, of course, unknown to Anderson in 1932.

To the right we show a bubble chamber photograph. A number of negatively charged pi mesons enters from the bottom; these are the beam particles, and have a momentum of 1.20 Gev/c. The mesons are moving at 99.331% of the speed of light.

One of the beam particles interacts with a proton to form a neutral lambda and a neutral K ; both of these leave no track in the bubble chamber since they have no electric charge. Both of these neutral particles then decay into charged particles, which do leave tracks in the chamber. The lambda decays into a proton and a negatively charged pi meson; the K decays into the positively charged pi meson and a negatively charged pi meson.

The diagram to the right shows a reconstruction of the interaction we see in the photograph.

The reason for the curvature of the tracks is that there is a magnetic field directed into the plane of the photograph. The figure to the right shows the curvatures due to positive and negatively charged objects. Note that for positively and negatively charged particles moving from the left to right, their curvatures are in opposite directions. It will turn out to be useful later to note that the curvature of a positively charged object moving from right to left is identical to the curvature of the negative object moving from left to right. By measuring the radius of curvature of a track in a bubble chamber we can determine the momentum of the particle.

The faster the particle is moving, the less curvature there is in its trajectory. Thus, the beam particles in the above bubble chamber photograph are almost straight because they are moving at almost the speed of the light.

The new particle that Anderson discovered has the following properties:

• The mass equals the mass of the electron.
• The charge has the same magnitude as the electron's charge, but is positive instead of negative.
• The particle is always created in pairs with electrons.
• When this particle collides with an electron, both annihilate.

The figure to the right shows another bubble chamber photograph, this time in which "pair production" occurred. The beam is a 2.60 GeV/c negative K meson , again entering from the bottom.

In the reconstruction of the event, shown to the right, the electron is labelled e - and the new particle that Anderson discovered is labelled e + . We call this new particle the antimatter electron or positron . It is now known that all so-called elementary particles have antimatter counterparts.

All the bubble chamber photographs and reconstructions of the events are from Harvey E. White, Modern College Physics 6th ed. (Van Nostrand Reinhold, 1972), pg 1011 and 1014.

The figure to the right is the spacetime diagram for pair production and subsequent annihilation of the positron. Light energy comes in from the lower left. It creates a positron-electron pair; this is a conversion of the light energy into mass energy. The positron goes along until it collides with some other electron, which causes both to annihilate; the mass energy is converted into light energy.

When the positron was discovered, Heisenberg was particularly elated. It was already known that the neutron was unstable, decaying into a proton and an electron. This naturally led some people to think of a neutron as being made of a proton and electron. With the discovery of the positron, Heisenberg could just as easily think of the proton as being made of a neutron plus a positron. As he later wrote: "The symmetry between the proton and neutron was restored ... In the beginning was symmetry!" (Reference: Physics and Beyond , pg. 132.) In this view the proton and neutron are made of each other. This is an example of what we shall later be calling a bootstrap .

A simple Flash animation of pair production and annihilation may be found here . The animation will appear in a separate window. It requires Version 5 or better of the Flash player, which is available free from http://www.macromedia.com/ . The file size if 4.7k.

Dirac's Theory of Antimatter

A comment by Dirac on why the positron was not discovered until 1932:

"Why did the experimentalists not see them? Because they were prejudiced against them. The experimentalists had been doing lots of experiments where particles were moving along curved tracks in a magnetic field. .... [They] sometimes saw the opposite curvature, and interpreted the tracks as electrons which happened to be moving into the source, instead of the positively charged particles coming out. That was the general feeling. People were so prejudiced against new particles that they never examined the statistics of these particles entering the source to see that there were really too many of them." -- Dirac, in J. Mehra, ed. The Physicist's Conception of Nature , pg. 12.

Note that Dirac is referring above to the fact we noted above that a negatively charged object moving from left to right in a magnetic field has the same curvature as a positively charged object moving from right to left.

If Dirac sounds a bit grumpy in the above quotation, there is a reason. He almost predicted the existence of the positron in 1930, before Anderson's discovery. He was musing about why the energy is always a positive number. He could think of no reason why this should be so. Applying a common physicists' assumption, that what is not forbidden is required, he concluded that there must be negative energy objects like electrons.

The next question, then, is why don't we observe these negative energy electrons. Dirac concluded that it must be because there is an infinitely dense totally homogeneous sea of these electrons everywhere in the universe. And since it is homogeneous it is unobservable.

Inayat Khan tells a Hindu story that has some relevance to this unobservable sea. A fish went to the Queen fish and asked: "I have always heard about the sea, but what is the sea? Where is it?" The Queen fish replied: "You live, move, and have your being in the sea. The sea is within you and without you, and you are made of sea and you will end in sea. The sea surrounds you as your own being." Reference: P. Reps, Zen Flesh, Zen Bones pg. 211.

Another example of a homogeneous and therefore unobservable structure is the now superfluous concept of an all-pervading luminiferous ether as a medium for light. Because this ether was homogeneous we could not detect it.

Now imagine that some light energy collides with a negative energy electron in Dirac's sea, knocking it into a positive energy state. This electron is observable. The hole it leaves in the sea is also observable, since it differs from the homogeneous negative energy sea around it. In fact, the hole will appear to have the mass of an electron. Further, its charge will appear to have the magnitude of the charge of the electron but will be positive. In fact, in Dirac's theory the hole is the positron!

When Dirac got this far, the positron was unknown. Thus he tried to interpret the hole as being a proton, but the mathematics of this theory didn't quite work out. When Anderson discovered the positron, Dirac immediately realised his theory described it perfectly. This theory of the positron is still routinely used.

The puzzle to the right was invented by Sam Loyd. The object of the puzzle is to re-arrange the tiles so that they are in numerical order.

The puzzle forms a model of how the positron moves in Dirac's theory. The numbered tiles represent the negative-energy electrons. The hole is the positron. When a negative-energy electron falls into the hole, the hole appears to have moved to another position.

What appears to be the annihilation of the positron when it collides with some other electron, then, is just the electron falling into the hole, giving up its energy as light.

Feynman's Theory of Antimatter

In 1949 Richard Feynman devised another theory of antimatter.

The spacetime diagram for pair production and annihilation appears to the right. An electron is travelling along from the lower right, interacts with some light energy and starts travelling backwards in time. An electron travelling backwards in time is what we call a positron. In the diagram, the electron travelling backwards in time interacts with some other light energy and starts travelling forwards in time again. Note that throughout, there is only one electron.

A friend of mine finds the image of an electron travelling backwards in time, interpreted by us as a positron, to be scary.

Feynman in his original paper proposing this theory wrote: "It is as though a bombardier flying low over a road suddenly sees three roads and it is only when two of them come together and disappear again that he realizes that he has simply passed over a long switchback in a single road." (Physical Review 76 , (1949), 749.)

Note that Feynman's theory is yet another echo of the fact, noted above, that a negatively charged object moving from left to right in a magnetic field has the same curvature as a positive object moving from right to left.

Feynman's theory is mathematically equivalent to Dirac's, although the interpretations are quite different. Which formalism a physicist uses when dealing with antimatter is usually a matter of which form has the simplest structure for the particular problem being solved.

Note that in Feynman's theory, there is no pair production or annihilation. Instead the electron is just interacting with electromagnetic radiation, i.e. light. Thus the whole process is just another aspect of the fact that accelerating electric charges radiate electric and magnetic fields; here the radiation process is sufficiently violent to reverse the direction of the electron's travel in time.

Nambu commented on Feynman's theory in 1950: "The time itself loses sense as the indicator of the development of phenomena; there are particles which flow down as well as up the stream of time; the eventual creation and annihilation of pairs that may occur now and then is no creation or annihilation, but only a change of direction of moving particles, from past to future, or from future to past." (Progress in Theoretical Physics 5 , (1950) 82).

About Formally Equivalent Descriptions

Above we noted that Feynman's theory of antimatter is formally equivalent to Dirac's theory. This means that the mathematics of either theory can be manipulated into the other one. Here is a nearly trivial example to illustrate. We say that there are two variables that describe some physical property: y and t . Perhaps y is the position of some object being acted on by various forces, and t is the time.

We imagine that some theory gives the relation between the two variables as:

Then we "read" the mathematics of the theory as a statement that tells us what the position of the object is for various times. We say that t is the independent variable, and that y is dependent on x . Here are some values:

Some other theory relates y and t according to:

Now we "read" the mathematics as a statement that says that for a given position of the object we can calculate when it was at that position. We say that now y is the independent various and t the dependent variable.

But the two equations are mathematically and formally equivalent to each other. Thus although the way we view whatever process is being described differently depending on which equation is being used, the underlying formalism is the same.

When we return to Quantum Mechanics, we will see another example of two formally equivalent theories. These are the Heisenberg form of Quantum Mechanics and the Schrödinger one. There we shall see that despite the formal equivalence, both Heisenberg and Schrödinger felt strongly about which one is "correct."

A Representation of Both Theories of Antimatter

"Day and Night" by M.C. Escher. Note that both Dirac's and Feynman's theory of antimatter are represented. This was not Escher's intention, of course. Instead, in this and much of his work he was focusing on figure-ground studies .

Thousands of years ago Chuang Tsu wrote a commentary that seems apropos for both Escher's drawing and these two theories of antimatter:

"It comes out from no source, it goes back in through no aperture. It has reality yet no place where it resides; it has duration yet no beginning or end. Something emerges, though through no aperture - this refers to the fact that it has reality. It has reality yet there is no place where it resides - this refers to the dimension of space. It has duration but no beginning or end - this refers to the dimension of time. There is life, there is death, there is a coming out, there is a going back in - yet in the coming out and going back its form is never seen." ( 23 , Watson trans.)

The figure to the right is a classic figure-ground study. Looked at one way the figure is a vase; from another perspective it is two faces. The distinction between the figure and the ground defining the figure is reminiscent for me of Dirac's infinite homogeneous sea of negative energy electrons.

Gestalt psychology uses figures like these. Some people have difficulty in seeing one or the other of the images, and these psychologists have devised techniques to aid people in learning to see both and switch back and forth between them. Of course, their goal in this is quite a bit more than just seeing both images in a figure-ground study.

Although most people can switch back and forth between the two ways of seeing the above figure, we can not see both at once. This reminds of so-called wave-particle duality for electrons: we can think of the electron as a wave or as a particle but can't think of it as both at once. The actual figure, though, is both the vase and the faces; similarly the electron is both a wave and a particle.

Why Is This Topic In The SYMMETRY Part of the Syllabus?

Recall that in the very early days of the universe, matter was created through pair production of electrons-positrons and protons-anti-protons. Does this mean that one-half of the matter in the universe is antimatter? Almost all experts in this field know the answer to the question. The problem is that some of the experts think the answer is "Yes" and others think the answer is "No."

Recall that a simple model of a hydrogen atom is a positively charged proton with a negatively charged electron in orbit around it. We can similarly have an anti-hydrogen atom with a negatively charged antiproton with a positively charged positron in orbit around it. This anti-hydrogen atom has been experimentally produced.

Similarly, we can have anti-helium, anti-molecules, etc.

It is certainly possible that there are antimatter galaxies, with anti-solar systems and maybe anti-people. In Dirac's theory we might say that the anti-people are holes in an infinite sea of negative energy people. They, of course, would say that we are holes in an infinite sea of negative energy anti-people.

Imagine that we get in radio contact with intelligent aliens from, say, the Planet of the Apes. With painstaking effort we establish a common language and end up in a state of good communication. One of the things that we want to communicate is the difference between left and right . It turns out that the only way to do this is to use the violation of mirror symmetry by weak interactions. So, we can have the aliens construct an apparatus like Madame Wu used in her classic experiment, and with that it is possible to define right and left.

However, if they are in an antimatter part of the universe, their anti-Madame Wu apparatus will get the definition backwards. So, if we set up a face to face meeting with the aliens and, having told them about some of our customs, when we meet they want to shake hands with us and extend their left hand, we better run!

Before the 1950's the validity of mirror symmetry was considered to be a nearly self-evident truth; you may recall that this symmetry is sometimes called conservation of parity . Yet another symmetry that used to be believed to be true is called charge conjugation : if we turn all particles into their anti-particles (and all anti-particles into their particles) everything will work the same. Now we know that neither parity or charge conjugation are completely conserved. But from the anti-Madame Wu experiments we can say that together they are conserved. Turn all particles into their anti-particles and then turn the whole system into its mirror image; the result will work the same. We shall have more to say about this in the next section of the syllabus titled Time's Arrow .

Symmetry and Conservation

In the previous section we sometimes talked about a symmetry, such as mirror symmetry, and sometimes describe the same circumstance in terms of a conservation of some quantity. There turns out to be a very close connection between symmetry and conservation.

For every symmetry, there is a corresponding conservation. The converse is also true: for every conservation, there is a corresponding symmetry.

For example, symmetry under spatial translation is equivalent to conservation of momentum. Symmetry under time translation is equivalent to conservation of energy. And symmetry under rotations is equivalent to conservation of angular momentum

Charge Conjugation, Parity, and Time Reversal

Above we indicated that in weak interactions such as used in Madame Wu's experiment, if we take the apparatus and construct a mirror image of it, and then take all the particles of the apparatus and turn them into their corresponding antiparticles, this new apparatus will work exactly like the original one. Sometimes, this is called CP Invariance , where the C stands for charge conjugation and the P for parity ie. mirror reflection.

There is a meson called the K 0 , which is electrically neutral and decays via the weak interaction into either:

• an electron, a positive pi meson and an anti-neutrino; or
• a positron, a negative pi meson, and a neutrino.

It turns out that the second mode is slightly preferred over the first.

The K 0 has an antimatter pair, the K bar 0 , which also decays via these same two modes, and for the anti-K meson the second mode is also slightly preferred over the first.

If one draws pictures of these decays, including the helicity states of the decay products, it isn't too difficult to realise that these experimental facts means that CP Invariance is violated.

However, according to our best understanding, if we:

• Turn all particles into their antiparticles (C); and
• Subject the decays to a mirror reflection (P); and
• Reverse the direction of time (T)

the combination of these three operations leaves the decay invariant. This is sometimes called CPT Invariance .

We summarize the invariance and symmetries that we have been discussing:

• Space translation, time translation, rotation: believed to be absolutely true.
• Mirror reflection (P): true for gravitational, electromagnetic, and strong interactions; not true for weak interactions.
• Turning particles into antiparticles + turning antiparticles into particles (C) + P: true for all interactions except for a small subset of weak interactions.
• C + P + reversing the direction of time (T): believed to be absolutely true.

A Great Question From a Former Student

Is the existence of symmetry due to the existence of non-symmetry?

A Final Speculation

Wheeler once called Feynman in the middle of the night, saying "There is only one electron in the universe!" The figure to the right shows what he meant. We assume the universe is closed. In Feynman's theory of antimatter, all the worldlines of the electrons and positrons connect so throughout there is only the one electron. This "explains" a mysterious fact: all electrons have totally identical properties.

U.S. issues travel warning for major European country: ‘Terrorist groups keep planning attacks’

• Updated: May. 04, 2024, 12:12 p.m. |
• Published: May. 03, 2024, 12:50 p.m.

(AP Photo/Michael Probst) AP

• Dr. Gracelyn Santos | [email protected]

The U.S. State Department has issued a new advisory urging travelers to Europe to be extra vigilant when visiting Germany due to concerns about potential terrorist activity.

The advisory, a Level Two – which suggests heightened caution— was released on May 1 and highlights ongoing threats from terrorist groups in Germany, cautioning travelers to remain alert as attacks could occur with minimal warning, noting that “terrorist groups keep planning attacks in Germany.”

The advisory states: “They target tourist locations and transportation hubs. They also target markets/shopping malls and local government facilities. They target hotels, clubs, and restaurants. They also attack places of worship, parks, and major sporting and cultural events. They target schools, airports, and other public areas.”

For reference, Level Three (Reconsider Travel) and Level Four (Do Not Travel) advisories represent more critical levels. However, Germany’s Level Two advisory is noteworthy, given its significant size in central Europe, robust economy, and second-largest population after Russia.

Over the past year, the most severe travel advisories in Europe were primarily linked to the conflict in Ukraine. Do-not-travel advisories were issued for Ukraine (May 2023), Belarus (July 2023), and Russia (September 2023) due to the ongoing hostilities.

If you must travel to Germany, the State Department recommends:

• Be aware of your surroundings when traveling to tourist locations and crowded public venues.
• Follow the instructions of local authorities.
• Monitor local media for breaking events and adjust your plans based on new information.
• Enroll in the Smart Traveler Enrollment Program ( STEP ) to receive Alerts and make it easier to locate you in an emergency.
• Follow the Department of State on  Facebook  and  Twitter .
• Review the Country Security Report for Germany.
• Visit the CDC page for the latest Travel Health Information related to your travel.

OTHER TRAVEL ADVISORIES ISSUED BY U.S. IN 2024

With Jamaica and Bahamas under travel advisories, which Caribbean islands are safe to book your next vacation?

Following ‘nationwide state of emergency,’ State Dept. issues travel advisory to South American spot

Amid do-not-travel alert, major cruise line stops visits to popular Caribbean resort

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A travel planner shares the 10 biggest mistakes people make while booking all-inclusive vacations

• As a travel planner, I regularly stay at all-inclusive resorts and book luxury trips for my clients.
• The vacations can be daunting and complicated to book, and many people make mistakes along the way.
• Booking the cheapest room , requesting an ocean view, and always bringing kids isn't the way to go.

As a travel planner at Marvelous Mouse Travels , one of my areas of expertise is booking all-inclusive vacations.

The luxury trips can be complex to book, so it's easy to get tripped up if you're new to them. And if you're spending upwards of $3,000 for a weeklong getaway for two, you want to ensure you're getting your money's worth.

Here are the biggest mistakes people make while booking all-inclusive vacations .

Jumping into internet searches before thinking about what you want

When choosing an all-inclusive resort , it's important to consider your dream vacation before you even start looking online. Determining a trip bucket list will greatly help to narrow down your search.

I encourage clients to think about things like their budget, nonnegotiable amenities, ideal locations, flight accessibility, desired room features, and resort size.

Booking the cheapest room at the cheapest resort

In all-inclusive travel, you truly get what you pay for.

I recommend focusing searches on properties with at least a 4.5 rating. Value properties often struggle to provide quality food options, comfortable accommodations, and adequate service.

Although entry-level rooms are the least expensive, booking them can also come at a price.

The cheapest rooms can have views of the parking lot or construction sites. Or they're located on the ground floor, which can get musty if you're in a humid, tropical location.

You can often upgrade to a better room for a minimal extra cost, and I think it's more than worth it. If you're really on a strict budget, shorten your trip by a day or two to allow for a higher-quality experience.

Taking your kids along every time

There are many great kid-friendly, all-inclusive resorts, but taking an adults-only trip is so much fun.

Grab your friends, family, or significant others to rewind for a few days without the kids.

On a recent trip to Le Blanc Spa Resort in Cancún, my husband and I appreciated the time we spent reconnecting, unwinding, and unplugging from work and family responsibilities.

Forgetting to research the food

One of the best parts of an all-inclusive vacation is enjoying the all-you-can-eat cuisine and top-shelf drink selections.

Spending up to a week at a luxury resort with mediocre food can be an unenjoyable experience. When reading reviews, p ay close attention to comments about the food quality.

I love the food and drinks at Palace, Sandals, and Beaches resorts and often recommend them to my clients.

Completely ruling out hurricane season

Booking a trip to the Caribbean or Mexico in summer and fall ( hurricane season ) carries some risk, but prices are usually significantly lower than at other times of the year.

The weather can be gorgeous, and there's no guarantee your trip will be impacted by bad weather. If you're concerned, definitely keep an eye on the weather and add on travel insurance while you're booking.

My husband and I honeymooned in the Caribbean in the fall , and the weather was some of the best I have ever had on a vacation.

Booking an ocean-view room

One of the biggest disappointments I hear from clients is that their view didn't meet their expectations.

Some resorts are more liberal with their categorization of partial-ocean-view and ocean-view rooms — maybe you can see a sliver of blue through the trees if you crane your neck.

If you want to see the beautiful blue of the sea from your balcony, you need to book an oceanfront room.

Limiting your search to tropical destinations

Many popular all-inclusive resorts are in tropical locations , but there are also some great options in places like Canada, Europe, and Japan.

Club Med offers all-inclusive resorts worldwide. One of its newest offerings is Club Med Charlevoix, which offers an all-inclusive ski experience in the winter and an adventure experience in the summer.

Trusting your friend's recommendations implicitly

Your friend might have impeccable taste, but that doesn't mean their favorite resort meets your style or needs.

One of my clients might love a resort, but another may not enjoy the experience at all. Finding the resort that's right for you is a very personal process.

Not booking with a travel planner

Sure, I'm a little biased, but hear me out: Choosing the right destinations and resorts for your all-inclusive vacation can be daunting. In Mexico alone, there are hundreds of lodgings to choose from.

Most travel planners offer complimentary services (we get commissions from hotels and other bookings), which can greatly reduce the headache of planning your trip.

I always look for the best pricing and make sure to support my clients before, during, and after their vacations so they can relax.

As part of being an agent, I also visit resorts to vet them for my clients. Reading reviews online can be helpful, but they can also be confusing, so I like to be able to make personal recommendations.

• Main content

American Academy of Arts and Sciences Elects Three NYU Faculty as 2024 Fellows

This year's selections are drawn from journalism, neural science, and physics.

The American Academy of Arts and Sciences has elected three New York University faculty as 2024 fellows: Glennys R. Farrar, a professor in the Department of Physics; André A. Fenton, a professor and chair of the Center for Neural Science; and Rachel L. Swarns, a professor in the Arthur L. Carter Journalism Institute. 

“We honor these artists, scholars, scientists, and leaders in the public, non-profit, and private sectors for their accomplishments and for the curiosity, creativity, and courage required to reach new heights,” said David Oxtoby, president of the academy. “We invite these exceptional individuals to join in the Academy’s work to address serious challenges and advance the common good.”

Among the 250 academy members elected this year are New York Times columnist Jamelle Bouie, Apple CEO Tim Cook, actor George Clooney, novelist Kim Thúy, and artist Rachel Harrison. The complete list of individuals elected in 2024, including 25 International Honorary Members, is available on the academy’s website .

Glennys R. Farrar , a theoretical physicist whose research spans particle physics, astrophysics, and cosmology, has made multiple breakthroughs including demonstrating that quarks are real and not just mathematical constructs, and developing key techniques to search for new phenomena at the Large Hadron Collider and with other instruments. Her work has addressed the nature of Dark Matter and Dark Energy, and the origin of the asymmetry between matter and antimatter. She and her students revealed the structure of the magnetic halo of the Milky Way and discovered the first examples of stars being consumed by supermassive black holes. Her current research is predominantly devoted to detecting Dark Matter with cosmological and experimental probes, discovering the origin of ultra-high energy cosmic rays and understanding the large-scale structure of the Galactic magnetic field.

André A. Fenton , a neuroscientist who studies how the brain stores experiences as memories and how it works to separate relevant from irrelevant information, has devised cognitive training methods for mice that can enhance the brain’s information processing, enabling “learning to learn.” His laboratory has also uncovered how distinct memories of similar events are represented in the brain and pinpointed a system that allows brain circuits to switch between processing current and recollected information—akin to how railroad switches control a train’s destination. With colleagues, Fenton also identified PKMzeta as a core molecular mechanism for how neurons store the information in memory, persistently for months despite the proteins degrading in days. In addition, Fenton’s work with mutant mice investigates how the genetic defect that causes Fragile X syndrome affects the process of learning and the coordination of information in the electrical activity of neurons that is a mixture of stored memories, environmental circumstances, and current state of mind.

Rachel L. Swarns , an associate professor of journalism, is a contributing writer for the New York Times whose research focuses on slavery and its legacies . She is the author of The 272: The Families Who Were Enslaved and Sold to Build the American Catholic Church (Random House, 2023), which emerged from her Times articles about Georgetown University’s roots in slavery, a series that touched off a national conversation about American universities and their ties to this history. She also penned American Tapestry: The Story of the Black, White and Multiracial Ancestors of Michelle Obama (Amistad/HarperCollins, 2012) and co-authored Unseen: Unpublished Black History from the New York Times Photo Archives (Black Dog & Leventhal, 2017.) Her newest project, “Hidden Legacies: Slavery, Race, and the Making of 21st Century America,” aims to deepen Americans’ understanding of the connections between slavery and contemporary institutions.

Academy members have included: Benjamin Franklin (1781), Alexander Hamilton (1791), Ralph Waldo Emerson (1864), Maria Mitchell (1848), Charles Darwin (1874), Albert Einstein (1924), Robert Frost (1931), Margaret Mead (1948), Milton Friedman (1959), Martin Luther King, Jr. (1966), Antonin Scalia (2003), Judy Woodruff (2012), John Legend (2017), Viet Thanh Nguyen (2018), James Fallows (2019), Joan Baez (2020), Sanjay Gupta (2021), Wesley Morris (2022), and Xuedong Huang (2023).

Alternate media contact: Alison Franklin, [email protected]

Press Contact

Sequoia National Park’s giants are the friendly type. Hugs are welcome.

People all over the world watched with rapt attention in 2021 as wildfire threatened to engulf the world’s largest tree . Firefighters carefully wrapped the base of the General Sherman Tree in shiny, protective blanketing as flames drew closer at Sequoia National Park .

Ultimately, the roughly 275-foot-tall icon was spared, but other giant sequoias weren’t so lucky. Redwood Mountain Grove in neighboring Kings Canyon National Park “lost an estimated 974 to 1,574 large sequoias,” according to Sequoia and Kings Canyon National Parks, which are managed jointly.

“Given the amount of giant sequoias that were lost in the last few years – almost 20% of the entire giant sequoia population was lost in a short amount of time – we're not feeling as confident as we were just a few years ago about these trees really being around for generations and generations to come,” said Sintia Kawasaki-Yee, chief of Communications and Management Support for both parks in California. “We really want to bring attention to their mortality.”

That’s not the only thing Sequoia visitors should know.

What is so special about Sequoia National Park?

Sequoia protects the largest trees in the world and a wide array of habitats.

“I would say the most special feature is that you enter at about, I want to say, 1,600 feet of elevation and within about a 45-minute span, you're able to reach 6,500 feet, which is a huge elevation gain in a really small amount of miles,” said Kawasaki-Yee. “You come in in the foothills area. In the spring, we have really great wildflowers. We have the river. We have great access there year-round, but if you drive just 45 minutes into Giant Forest , you get to see the change in the terrain and wildlife.”

Visitors can feel the change too, as temperatures dip and winds whip higher up, so pack accordingly.

Is the General Sherman Tree the tallest tree in the world?

No. It’s not the tallest tree in the world. That title belongs to Hyperion, a coast redwood at Redwood National Park, according to Guinness World Records .But the General Sherman Tree is the largest by volume, with a  trunk volume of 52,508 cubic feet, according to the park.

Can you touch the General Sherman Tree?

No. “The Sherman Tree is fenced off, so you cannot touch it, but there are many other sequoias in that same area that you can definitely walk up to and touch,” said Kawasaki-Yee. 

She recommends feeling their fibrous bark, which she noted is softer to the touch than one might expect.

“Feel free to hug a tree, connect with a tree,” she added. “That connection is really important to really build that connection for people and hopefully that commitment to protect these trees in the long term.”

From Acadia to Zion: What travelers should know about each of America's national parks

Which park is better, Redwood or Sequoia?

“They're basically siblings, and so it's like comparing your kids,” Patrick Taylor, Interpretation and Education manager for the National Park Service at Redwood , told USA TODAY in April. “You love them both for slightly different reasons.”

He explained that giant sequoias tend to have more volume to them.

“So they're bigger in the sense that they usually have a wider base, and they don't taper off as fast,” he said. “The coastal redwoods are usually a little taller and a little more slender.”

Is Sequoia National Park free?

No. Most visitors will have to pay a flat $35 vehicle entrance fee that covers access to both Sequoia and Kings Canyon.

Certain groups are eligible for free entry to all national parks, namely military service members, veterans, Gold Star families , U.S. citizens and permanent residents with permanent disabilities, and fourth graders and their families .

Can you just drive through Sequoia National Park?

Yes. “You can actually do both parks in one drive,” said Kawasaki-Yee. “A lot of people that are doing road trips will drive through both parks on the same day or the same trip.”

The park is located about an-hour-and-a-half drive from Fresno. Fresno Yosemite International Airport is the nearest commercial airport.

What is the best time of year to visit Sequoia National Park?

Kawasaki-Yee recommends visiting in the spring or fall to avoid summer crowds and winter road closures.

“Maybe right before Memorial Day weekend, so you don't get the crowds but you still get access to the areas,” she suggested.

Can I stay inside Sequoia National Park?

Yes. The park offers a variety of on-site camping and lodging , though some lodges, operated by third parties, only open seasonally.

Who are the Indigenous people of the area?

“Sequoia and Kings Canyon National Parks are the homelands of the Mono (Monache), Yokuts, Tübatulabal, Paiute, and Western Shoshone,” according to the parks’ website, which lists the following affiliated federally recognized tribes:

• Big Pine Band of Owens Valley Paiute Shoshone Indians
• Big Sandy Rancheria Band of Western Mono Indians
• Bishop Paiute Tribe
• Bridgeport Indian Colony
• Cold Springs Rancheria
• Fort Independence Indian Community of Paiute Indians
• Fort Mojave Indian Tribe
• North Fork Rancheria of Mono Indians
• Paiute-Shoshone Indians of the Lone Pine Community
• Picayune Rancheria of the Chukchansi Indians
• Santa Rosa Rancheria Tachi-Yokut Tribe
• Table Mountain Rancheria
• Tejon Indian Tribe
• Tule River Tribe
• Utu Utu Gwaitu Paiute Tribe of the Benton Paiute Reservation

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