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# What are Antiatoms Made Of?

Asked by Keith Cannon, student, Union Central on March 13, 1997:
What would an "antiatom," made up of the antiparticles to the constituents of normal atom, consist of? What might happen if antimatter, made of such antiatoms, came in contact with our normal world of matter?
Before explaining what antiatoms are, it would benefit some of our readers to explain what particles and antiparticles are. As most of us know, most matter that we can see is made up of atoms which are in turn composed of various combinations of three particles: electrons, protons, and neutrons. These three particles, together with a wide variety of other more obscure particles, are the basis for all matter.

It has been found that for each of these particles, there is a dual "antiparticle." The dual of the electron is called the positron, while the duals of the proton and the neutron are simply called antiprotons and antineutrons. Antiparticles behave very much the same as ordinary particles. They have the same mass as their particle counterparts, but the charge of an antiparticle is opposite the charge of the corresponding particle.

Just as protons, electrons, and neutrons often cluster together to form atoms, antiprotons, positrons, and antineutrons can combine to form antiatoms. The properties of antimatter are very similar to that of normal matter. While only very basic antiatoms like antihydrogen have been made in laboratories, some scientists believe that there may be entire galaxies composed almost entirely of antimatter.

Perhaps the most interesting thing about antimatter is what it does when it comes in contact with normal matter. When a particle collides with its antiparticle counterpart, the two annihilate each other and give off a burst of energy. The amount of energy given off is given by Einstein's famous formula E = mc^2 where E is energy in Joules, m is the mass in kilograms and c = 3 x 10^8 m/sec is the speed of light. Similarly, when atoms and antiatoms collide, they also destroy one another and release energy. To give an idea of just how much energy is produced, consider a paper clip (about 1 g in mass) combining with an antipaperclip. The energy produced would be E = (2 x 10^(-3))(9 x 10^(16))=1.8 x 10^(14) Joules. For the sake of comparison, it takes about 3 x 10^9 Joules to power a 100 Watt light bulb for a year.

Followup Question by Brent Potteiger on March 30, 1997:
I understand the concept of E=mc^2, and after reading your article about antiatoms (and figuring out that two grams of matter could create enough energy to power approximately 60,000 100 kilowatt light bulbs for a year) I don't understand why we don't harness the power to convert matter completely into energy. Wouldn't that save all of our energy needs?
At the present we do not have an efficient way of making antimatter. To harness the energy in matter we would need to take one of two approaches.

One would be to generate antimatter. The only known methods of accomplishing this involve starting with energy and then converting it into antimatter. The methods for doing so are very inefficient and are only of use (so far) in that they allow us to study the behavior of antimatter. The energy resulting from the antimatter created would be far to little to make up for the massive amounts of energy it took to generate the antimatter. Also, at the present, the amount of antimatter that can be generated by even a very large collider is on the atomic level. Even if we could efficiently generate antimatter, we would need to be able to do it on a much larger scale.

Another approach would be to discover a source of naturally occurring antimatter. While natural antimatter likely does exist, it is likely (and hopefully) far away. Because it reacts so readily with matter, it is typically not found anywhere near matter.

Another problem is the means by which one might contain the antimatter and then capture the energy once it reacts with matter. Containing antimatter is no small feat since it must be stored in something which is not made of matter. Currently electric and magnetic fields are used, though it is not clear how one would use this sort of containment device on any more than a few atoms or particles.

The energy produced in antimatter/matter reactions is in the form of gamma rays. This is similar to the case of fission reactor, where water is heater and used to drive a turbine. The problem is that, even though there is no inherent radioactivity in the matter or antimatter, anything which comes into contact with the reaction will eventually become radioactive. There is no waste, though there is still the problem of what to do with an old power plant which has itself become radioactive over the years.

As a closing remark, all the basic theory is in place for extracting energy from nuclear fusion. A fusion reaction is much easier to implement than a matter-antimatter reaction but is still a long way from perfection. Some experimental fusion reactors have been built, but currently they are, at best, breaking even (they require as much energy to run as they produce). The problem is not with fusion as an energy source, but rather with the practical aspects of how to get the reaction going and then efficiently harness energy from it.

Followup question by an anonymous student on September 28, 1997:
So, why do matter and antimatter release energy when combined?
One of the great breakthroughs of this century was the discovery that mass was itself a type of energy. This energy can be converted into other, more conventional sorts of energy only in special cases though. One of these instances is a matter/antimatter reaction (other examples are nuclear fusion and fission). When matter and antimatter destroy one another, they must release the energy that was stored in their mass (energy is always conserved). This energy is typically in the form of a very high energy light particle called a gamma ray. The amount of energy which is stored in the mass of a particle is given by Einstein's famous formula E = mc^2 (E is energy in Joules, m is mass in kilograms, and c is the speed of light in a vacuum in meters per second).

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