Antimatter sounds like the stuff of science fiction, but it’s very real. It is, however, elusive.
Antimatter particles are subatomic particles with properties opposite those of normal matter particles. So a positron (positively charged) is the antiparticle equivalent of the electron (negatively charged). When a particle and its antiparticle meet, they annihilate (are destroyed), releasing a lot of energy.
Antimatter particles are created in ultra high-speed collisions. There was a lot of it after the Big Bang. But today antimatter is rare.1
How rare is antimatter? Lawrence Krauss puts it this way:
I like to say that while antimatter may seem strange, it is strange in the sense that Belgians are strange. They are not really strange; it is just that one rarely meets them.2
In the sentences before making that statement, Krauss tells us something interesting about antimatter:
Because antiparticles otherwise have the same properties as particles, a world made of antimatter would behave the same way as a world of matter, with antilovers sitting in anticars making love under an anti-Moon. It is merely an accident of our circumstances, due, we think, to rather more profound factors…that we live in a universe that is made up of matter and not antimatter or one with equal amounts of both.3
That’s pretty awesome! You might be wondering then, how can we know that this universe is made of matter and not antimatter? If they behave the same way, how can we tell the difference? Antimatter has an opposite charge and quantum spin4; those are the subtle differences that let us know that we live in a universe comprised of matter. Well, there’s that and the possibility that it falls up.5
Every particle in existence has an antiparticle equivalent, which is almost identical except it carries the opposite electric charge. Matter is composed of normal particles and antimatter is composed of antiparticles—for example, while a proton and an electron form an ordinary hydrogen atom, an antiproton and a positron form an antihydrogen atom. Antimatter is created all the time in high-energy collisions, like when cosmic rays impact Earth’s atmosphere, but it immediately disappears because when matter and antimatter collide, they annihilate in a flash of pure energy. This makes it difficult to study experimentally, and neither can we find any evidence of a significant concentration of antimatter in the wider universe. The universe we know is dominated by ordinary matter—it makes up every person and planet and star—and yet if matter and antimatter were created equally at the birth of the universe, where has all the antimatter gone? This asymmetry is a perplexing question in physics, and several theories have been proposed to explain it. Perhaps nature favours matter reactions over antimatter ones; or perhaps matter and antimatter particles decay differently; or perhaps there are far flung regions composed primarily of antimatter, but they’re just beyond our visible universe. Researchers are currently trying to determine if such regions exist by studying colliding superclusters for high-energy signatures of annihilation, and by studying decay patterns in quarks.
The universe is a weird place. Here’s a look at some of the strangest things in the cosmos.
Like Superman’s alter-ego, Bizzaro, the particles making up normal matter also have opposite versions of themselves. An electron has a negative charge, for example, but its antimatter equivalent, the positron, is positive. Matter and antimatter annihilate each other when they collide and their mass is converted into pure energy by Einstein’s equation E=mc2. Some futuristic spacecraft designs incorporate anti-matter engines.
2. Mini-Black Holes
If a radical new “braneworld” theory of gravity is correct, then scattered throughout our solar system are thousands of tiny black holes, each about the size of an atomic nucleus. Unlike their larger brethren, these mini-black holes are primordial leftovers from the Big Bang and affect space-time differently because of their close association with a fifth dimension.
3. Cosmic Microwave Background
Also known as the CMB, this radiation is a primordial leftover from the Big Bang that birthed the universe. It was first detected during the 1960s as a radio noise that seemed to emanate from everywhere in space. The CMB is regarded as one of the best pieces of evidence for the theoretical Big Bang. Recent precise measurements by the WMAP project place the CMB temperature at -455 degrees Fahrenheit (-270 Celsius).
4. Dark Matter
Scientists think it makes up the bulk of matter in the universe, but it can neither be seen nor detected directly using current technologies. Candidates range from light-weight neutrinos to invisible black holes. Some scientists question whether dark matter is even real, and suggest that the mysteries it was conjured to solve could be explained by a better understanding of gravity.
Until about the early 1990s, the only known planets in the universe were the familiar ones in our solar system. Astronomers have since identified more than 500 extrasolar planets (as of November 2010). They range from gargantuan gas worlds whose masses are just shy of being stars to small, rocky ones orbiting dim, red dwarfs. Searches for a second Earth, however, are still ongoing. Astronomers generally believe that better technology is likely to eventually reveal worlds similar to our own.
6. Gravity Waves
Gravity waves are distortions in the fabric of space-time predicted by Albert Einstein’s theory of general relativity. The gravitational waves travel at the speed of light, but they are so weak that scientists expect to detect only those created during colossal cosmic events, such as black hole mergers like the one shown above. LIGO and LISA are two detectors designed to spot the elusive waves.
7. Galactic Cannibalism
Like life on Earth, galaxies can “eat” each other and evolve over time. The Milky Way’s neighbor, Andromeda, is currently dining on one of its satellites. More than a dozen star clusters are scattered throughout Andromeda, the cosmic remains of past meals. The image above is from a simulation of Andromeda and our galaxy colliding, an event that will take place in about 3 billion years.
Neutrinos are electrically neutral, virtually mass-less elementary particles that can pass through miles of lead unhindered. Some are passing through your body as you read this. These “phantom” particles are produced in the inner fires of burning, healthy stars as well as in the supernova explosions of dying stars. Detectors are being embedded underground, beneath the sea, or into a large chunk of ice as part of IceCube, a neutrino-detecting project.
These bright beacons shine to us from the edges of the visible universe and are reminders to scientists of our universe’s chaotic infancy. Quasars release more energy than hundreds of galaxies combined. The general consensus is that they aremonstrous black holes in the hearts of distant galaxies. This image is of quasar 3C 273, photographed in 1979.
10. Vacuum Energy
Quantum physics tells us that contrary to appearances, empty space is a bubbling brew of “virtual” subatomic particles that are constantly being created and destroyed. The fleeting particles endow every cubic centimeter of space with a certain energy that, according to general relativity, produces an anti-gravitational force that pushes space apart. Nobody knows what’s really causing the accelerated expansion of the universe, however.
Black holes and pulsars radiate thick jets of particles, comprised of electrons and their anti-particle partner – the positron. Astronomers are able to observe the jets but are unable to directly study and analyze them due to their distant locations in the universe. The exact particle composition and energy content of the jets remains a mystery. With the help facilities such as CERN, physicists are able to smash particles together in an attempt to understand the fundamental particles seen in these cosmic jets and plasma.
For every particle in our universe, there is an equal and opposite particle called an anti-particle with positrons being the anti-particle of electrons. Until recently, the only way to mass produce and analyze such particles was by means of vast underground particles accelerators like the Large Hadron Collider (LHC); however, thanks to a team of researchers at the University of Texas, the LHC’s capabilities are now available in a more convenient desktop version. An international team of physicists from the University of Michigan have gone one step further and developed an “anti-matter gun”, approximately one meter in length and capable of generating short bursts of positrons and electrons just like the ones emanating from black holes.
To create these particle bursts, the team ionized a sample of inert helium gas by firing a petawatt (quadrillion watt) laser beam at it, generating a high-speed electron stream. The electron stream was then focused on super thin sheets of copper, tin, tantalum and lead, causing them to collide with individual metal atoms and yielding a stream of shorter, denser bursts of electrons and positrons, than typically produced by larger particle accelerators. Simply stated, the team used a quadrillion watt laser, fired it for approximately thirty quadrillionths (30 femtoseconds) of a second and produced quadrillions of positrons – statistics comparable to CERN!
The new laser-based “anti-matter gun” is one of the only methods able to produce jets and plasma bursts simultaneously, enabling the team to directly observe and analyze how the particle jets and plasma interact. Researchers are optimistic these new results will lead to better understanding of anti-matter, black holes and the jets they produce.
The image seen here is an artist impression of particle jets emanating from a black hole.
A Black Hole Doesn’t Die – It Does Something A Lot Weirder
Black holes are basically “game over, man,” for anything that gets too close to them, but they aren’t invincible. In fact, they’re always in the process of self-destructing. We’ll look at how they fizzle out, and see if we can help them do it faster.
The Event Horizon
Realistically speaking, you are dead as soon as you get anywhere near a black hole. You’ll be snapped like a rubber band by the differences in the gravitational pull on your top and bottom half, or you’ll be fried by radiation (more on that later). No one in the foreseeable future (even if we try to foresee multiple millennia into the future) will get close to a black hole. Pass the event horizon, however, and you don’t even have an unforeseeable future. Once material gets beyond the event horizon, it’s being pulled into the black hole with such force that it doesn’t escape. Not even light gets out. Once something has gone beyond the event horizon, it no longer really “counts” as part of the universe anymore.
We Captured Antimatter for 16 Minutes: What Does That Mean
One of my favorite things about the universe is that it shouldn’t exist. Not in like an existential why are we even here? way, but in a real-deal “god who?” science-says-so way. It should have blown itself up just as quickly as it Big Banged its way into existence.
That’s because of antimatter, the stuff that is opposite to “proper” matter in every way and when it comes in contact with regular old matter (ROM), will annihilate both itself and the ROM in a flash of gamma rays. Paul Dirac figured antimatter out in 1928 while working to put Einstein’s theory of relativity together with quantum mechanics. He realized that for electrons to exist, they needed to have an antielectron partner. All of them, and all of the ROM should have immediately met its antimatter mirror and annihilated before any of the great This could have happened.
Quirky Quarks: ‘Charming’ Particle Mixes with Bizarre Cousin
An experiment that offers a peek inside the behavior of subatomic particles called quarks could help answer questions about why the universe is made of matter, and might even be evidence of new, previously unseen particles.
At the Fermi National Accelerator Laboratory (Fermilab) in Illinois, an international team of scientists published the first observation of a charm quark (quarks come in several “flavors”) decaying into its antiparticle, a phenomenon called “mixing,” first predicted in 1974.
While the Large Hadron Collider is looking for the Higgs boson, we’re on the verge of two huge antimatter-related breakthroughs. One could finally solve the universe’s oldest mystery, while the other could reveal strange new particles that are perfect for quantum computers.
The first result comes from CDF, one of the two long-running experiments at the now deactivated Tevatron accelerator at Fermilab. CDF physicists had been studying the decay of subatomic particles called D-mesons - particles made up of massive charm quarks that form in the decay of even heavier bottom quarks, which in turn decay into kaons and pions.
The other big antimatter-related result hasn’t come from a big particle accelerator but instead a nanowire in a Dutch laboratory. According to a team led by Leo Kouwenhoven of the Delft University of Technology, they have spotted what could be the first experimental evidence of Majorana particles, first proposed by Ettore Majorana over 70 years ago. These theoretical particles are a unique exception to the standard relationship of matter and antimatter, in that they don’t annihilate each other when they come into contact. Majorana realized in 1937 that a fermion with no electric charge would have a completely identical antiparticle, meaning pairs of these particles would be able to exist together without destroying one another. They’re remained strictly theoretical until now, when Kouwenhoven reported the first tentative evidence of their existence.