10. Dirac: The Anti-Einstein

One of Albert Einstein's key scientific contributions was the E = mc2 equation (energy = mass x the speed of light squared), which basically states that matter can be turned into energy and vice-versa.

Yet in 1928, British physicist Paul A.M. Dirac revised Einstein's equation to suggest that mass could theoretically have negative properties, not just positive ones.
Enter Dirac's equation: E = +/-mc2.

Dirac theorized the existence of positrons, or particles with the same mass as normal electrons yet with a positive charge. If true, this would mean that every particle possesses an opposite.

As it turns out, the particles occur naturally thanks to the radioactive decay of some atoms. U.S. physicist Carl Anderson confirmed the existence of antimatter in 1932 when he discovered positrons while studying cosmic rays.  The following year, British physicist Patrick M.S. Blackett and Italian Giuseppe Occhialini backed up the controversial claim.

9. Missing Antimatter Mystery

Each type of particle has its antiparticle, leading to some inevitable cosmic quandaries. First, we're surrounded by matter; where did all the antimatter go?

We can even ask this question because when antimatter meets matter, they destroy each other. This leads to the second question: Why didn't all the antimatter destroy all the matter early in the universe? Physicists think the big bang should have produced equal amounts of both matter and antimatter. In other words, the universe should have poofed all matter and antimatter out of existence.

While we're still not sure why the cosmos turned out this way, scientists predict matter won out by a very small margin via some yet-to-be-discovered physics. Any way you dice it, though, it seems we're the mere remnants of an epic clash that occurred at the beginning of time.

8. Antimatter Spied from Balloons

Matter and antimatter simply don't mix. Bring the two together, and you get a massive burst of energy in the form of gamma rays. Thankfully antimatter is so rare that you don't have to worry about, say, shaking hands with your anti-self and flashing out of existence.

So you can imagine how surprised scientists were in 1978 when their balloon-mounted gamma ray detectors indicated positron-electron reaction gamma rays originating from space.

The high-energy beams seemed to indicate that a 10,000 light-year-wide cloud of antimatter surrounds the galaxy's core. That's a lot of antimatter, and scientists disputed possible causes for years. Then, in January 2008, the European Space Agency's International Gamma-Ray Astrophysics Laboratory (INTEGRAL) placed the blame squarely on black holes and neutron stars.

When such dead stars consume anything unlucky enough to wander nearby, the matter falling onto the dead stars creates an intense field of radiation. INTEGRAL scientists think that the field randomly combines to form both electrons and positrons -- and the cloud.

7. Let's Smash Some Atoms

Carl Anderson may have identified a positron in 1932, but it would be 1955 before anyone found that theoretical negative proton, or antiproton. This elusive particle didn't form during radioactive decay -- the only way physicists could hope to observe an antiproton was to make one in the lab.

To verify an antiproton, you need a particle accelerator capable of producing 6 billion electron volts, not to mention some way to "see" it. It wasn't until 1954 that a rag-tag group of physicists got their hands on an accelerator up to the task: the Bevatron at Lawrence Berkeley National Laboratory in California.

To create antiprotons at the Bevatron, approximately 40,000 different particles need to spring into existence at that same moment. Even then, positrons last just one ten-millionth of a second before they meet a proton and vanish. The researchers eventually spotted the particles by pinpointing their death signatures -- called annihilation stars -- amid the photographic documentation.

6. Anti Atoms

It's one thing to smash atoms and create a few brief antiprotons. It's another task entirely to combine a positron (electron antimatter) and an antiproton (proton antimatter) to create an antimatter hydrogen atom.

Four decades would pass after the formation of the first man-made antiproton before technology permitted anti-atom creation.

CERN researchers in Europe successfully created antihydrogen in 1995 by speeding antiprotons past normal atoms at close to the speed of light. Occasionally, an antiproton came close enough to a nucleus of normal matter to create an electron-positron pair. By an equally slim chance, the resulting positrons occasionally paired up with a passing antiproton -- resulting in antihydrogen.

5. Antimatter from the Sun

We spent decades researching and developing miles-long particle accelerators to make some antimatter. For the sun, however, antimatter creation is a day-in, day-out business.

Solar flares release vast quantities of energy and the largest, according to NASA, are equivalent to a billion one-megaton nuclear bombs detonating all at once -- an explosion large enough to smash atoms.

In 2002, scientists observed a solar flare do this with NASA's Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) spacecraft. While spying on the flare's emitted radiation, they spotted the sudden creation (and subsequent destruction) of roughly a pound of antimatter. This small quantity of antimatter harnessed a ridiculous amount of energy -- enough to power whole countries for years.

4. Dreams of an Antimatter Engine

If you think antimatter sounds like a dream fuel, you're not alone. Scientists and futurists have put a lot of thought into the promise of an antimatter engine. Even NASA put forth early designs for antimatter spacecraft, complete with special magnetic storage rings to safely house the vital antimatter.

Combine a small quantity of antimatter with good old "classic" matter and -- bam! -- you have all the power you could possibly need. According to NASA, the energy produced by a gram of antimatter meeting a gram of normal matter would equal that of the thrust behind 1,000 external space shuttle fuel tanks.

The concept isn't that fundamentally different from a rocket engine, where a combination of fuel and an igniting agent produce the explosive trust. Problem is, antimatter happens to be one of the most expensive-to-produce materials in the universe.

3. Antimatter Factories

Could we ever get all the antimatter we need to generate power? One popular idea is to develop it in factories.

The downside is that we currently produce little precious antimatter. All the antiprotons CERN cranks out in a year would barely be enough to provide three seconds of electric lighting. Yet, according to the Journal of Propulsion and Power, a mere millionth of a gram would be enough to power a one-year flight to Mars.

There's no way of reaching vast antimatter deposits near the center of the galaxy, so we can't mine antimatter -- or can we? Antimatter-creating solar flares just might do the trick. One NASA-funded plan called for the use of giant wire spheres to harvest these particles as they reach Earth's orbit; a positively charged wire would attract negatively charged antiprotons, while repelling any pesky protons that would annihilate the antimatter stash.

2. Cosmic Home Remedy: Antimatter

It's not a stretch to envision a future where antimatter starships speed through the galaxy or antimatter weapons reduce whole nations to dust. But you might be surprised to learn that -- just as atomic energy is used to produce X-rays and fight cancer -- antimatter is also chock full of medical benefits.

For instance, we regularly use low-level electron-positron annihilations to perform positron emission tomography (PET) scans. Doctors inject a patent with a radioactive fluid which, as atoms in it, gives off positrons.

This antimatter then collides with electrons to produce gamma rays, which are then converted into photons. Special digital camera sensors pick up the photons and amplify the signal to produce a digital image of what's going on inside living tissue. Nifty.

1. Antimatter Stars and Galaxies

We may not fully understand the reasons for a universe lopsided in favor of regular ol' matter, but it's the reason matter won out at the dawn of time -- and antimatter was reduced to its current, meager role in the observable universe.

But this mystery begs the question: Could there be whole stars out there somewhere composed of antimatter? Or even a galaxy in which anti-atoms are the status quo?

An antimatter star may not differ that much from a typical star. Its light would be indistinguishable as the same physical properties apply -- it's merely the material involved that is different. Of course, a theoretical anti-sun would have to exist beyond the reach of matter -- as in, it would have had to have survived all the collisions and mingling of dusts and bodies that birthed the observable universe. Likewise, an antimatter galaxy would have to exist far from those composed of regular matter.

When you get right down to it, the Milky Way is the only galaxy we're 100 percent certain is made of matter! The chance is extraordinarily slim, but any of the 2 million galactic superclusters out there could be pure antimatter. The light that reaches our little world would be indistinguishable, either way.