Physics

# Antimatter the Basics

Tweet
William Logan's image for:
"Antimatter the Basics"
Caption:
Location:
Image by:

Perhaps nothing in the entire lexicon of actual science invokes more vivid futuristic images than the term antimatter. After all, antimatter was the fuel of choice for all of Starfleet Command and the Starship Enterprise in particular. In the new novel "Angels and Demons" a bomb is created from antimatter stolen from CERN, and stories of an endless supply of clean energy are common. Unfortunately, the truth throws a big wet blanket on our imaginations.

Matter and antimatter are mirror images of each other. An electron and positron are identical in every measurable way but have opposite electric charge. When the two come into contact they annihilate each other, converting all their mass into energy in a flash. Mass and energy are different manifestations of the same thing and are related by Albert Einstein's famous equation E=MC2. So, since "c" is the speed of light and is 2.9x108 m/s and "c2" is 8.4x1016, when matter and antimatter collide the amount of energy released is enormous. One single gram of matter could supply all the energy needs of an average town for a day.

In 1929, as Paul Dirac completed his set of equations describing the electron, he was puzzled by the quadratic (containing a squared variable) component of his creation. This gave the equations two sets of equally valid solutions, one positive and one negative. For Dirac, this meant that either he had committed an error in constructing his equations, the quadratic was an anomalous mathematical fluke, or that some component of the properties of an electron was reversible. He considered the possibility of an electron with a negative energy and initially dismissed the idea as it made no sense in classical physics, but the hunt for antimatter was underway.

Two years after the discovery of high energy cosmic rays in 1930 physicist Carl Anderson was observing their behavior in a cloud chamber when he noticed a particle that behaved like "something positively charged with the same mass as an electron". He ultimately realized that he was watching an antimatter electron, which he named the positron. With the construction of increasingly powerful cyclotrons and the birth of "high energy physics" in the 1950's the discovery of the antielectron was followed by the antiproton and antineutron. Recently, as scientists have developed ways to trap and control antiparticles, the antideuteron nucleus was formed by combining an antiproton and antineutron and antiatoms were finally made when antielectrons were combined with an antiproton to make antihydrogen in 1995.

Scientists speculate that when the universe was about one ten billionth of a second old and about the size of a school bus there was essentially an equal amount of matter and antimatter. The temperature was so hot that matter and antimatter pairs were being constantly created and destroyed in the dense, primordial plasma. For a reason that is not clear the symmetry in the quantities of matter and antimatter was broken, and matter gained a slight advantage, approximately 1,000,000,001 particles of matter for every 1,000,000,000 particles of antimatter. Had that symmetry not been broken, all the matter in the universe would have been converted into energy as the universe became too cool for the creation of new matter-antimatter pairs and the existing pairs annihilated each other. That one extra particle of matter as we know it became all the matter left in the universe.

So why not gather up a bunch of antimatter and combine it with regular matter and harness the phenomenal volume of energy released. Well, antimatter is just too hard to come by. It is produced in colliders that accelerate particles up to speeds approaching the speed of light and then slam them into a metal target, producing energies approaching those moments after the big bang. Despite the energy released when antimatter and matter collide, it is a fraction of the energy necessary to create the antimatter in the first place. Something on the order of one ten billionth of the energy invested in the creation of antimatter is released upon annihilation. There is no conceivable way, even theoretically, to produce antimatter in a way that yields more energy when it reacts with matter than was required for production, so it will not be a fuel or a weapon unless we stumble upon a secret cache somewhere out in the universe, a perfect undertaking for the Starfleet.

Tweet