Facts About Antimatter Articles
What is antimatter? It is part of the plot in Dan Brown's book Angels and Demons--that's what. Dan Brown writes an engaging story. It is fiction, of course. But antimatter itself is real.
The first particle of antimatter ever to be discovered was the positron. In 1932 Carl Anderson found its tracks while investigating cosmic rays. A positron is the antimatter opposite of an electron. It has the same mass as an electron, generates the same amount of magnetic field, and has the same amount of charge. But its charge is positive, while the electron's is negative. The two are exact opposites. If a positron and an electron meet, they can annihilate each other, leaving only energy in the form of light (gamma rays) in their wake.
Since 1932, physicists have postulated that every normal particle of matter has an antimatter counterpart. For protons there are antiprotons; for neutrons there are antineutrons; for neutrinos there are antineutrinos; and so on. In many cases, these antiparticles have been actually observed when high energy particles smash into one another at particle accelerator facilities like CERN. (But don't worry. Significant amounts of antimatter cannot be accumulated, because no vacuum trap for antimatter could permanently protect against every stray particle from cosmic rays and other sources. It takes only a one such particle to put energy into the system and seriously disrupt its stability.)
The discovery of the positron in 1932 has a remarkable story that goes with it. 1925 and 1926 saw the appearance of fundamental advances in the field of quantum mechanics, which described the behavior of electrons and other small particles. But the quantum mechanics of 1926 did not agree with the special theory of relativity developed by Einstein in 1905. Both theories seemed to work at least fairly well in their own sphere. But they were incompatible when taken together.
So in 1928 Paul A.M. Dirac tried to tinker with quantum mechanics, searching for an alteration that would make it compatible with the special theory of relativity. Dirac came up with an equation that combined the two theories and that accurately described the behavior of electrons.
But close examination of the mathematics showed that it represented an electron with not only one state, but four states. This result was totally unexpected, and at first it puzzled Dirac himself. Two of these states correspond to electrons with up and down spin, respectively. The other two correspond to positrons with up and down spin. But no one knew that positrons existed! Anderson's discovery of the positron was to come four years later.
The mathematics had predicted a new particle beforehand. It is in fact one of the most impressive predictions in the whole history of science. Scientists were not even looking for antimatter. And mathematics seemingly of its own accord told them it was there.
How in the world could it do that? Up to a point, we can understand the reverse process, where a scientist travels from physical observations toward mathematical formulations. A carefully crafted equation in mathematics can approximate experimental data that a physicist already has in hand. But the process with Dirac went in the other direction. Make up some mathematics that melds together two incompatible theories. And in order to work, the mathematics requires the existence of antimatter.
Twentieth century physics has uncovered not one but a whole host of striking illustrations of connections between mathematics and the physical world. Nobel laureate Eugene Wigner was so struck by it that he wrote an article, "The Unreasonable Effectiveness of Mathematics in the Natural Sciences," Communications on Pure and Applied Mathematics 13 (1960) 1-14:
The first point is that the enormous usefulness of mathematics in the natural sciences is something bordering on the mysterious and that there is no rational explanation for it. (p. 2)
It is not at all natural that "laws of nature" exist, much less that man is able to discover them. (p. 5)
Eugene Wigner finds no rational explanation. But theoffers one:
In the beginning was the Word, and the Word was with God, and the Word was God. He was in the beginning with God. All things were made through him, and without him was not any thing made that was made. (John 1:1-3)
The Word of God, the second Person of the the harmony of God's mind, and the harmony between the persons of the Trinity., expresses the rationality and wisdom of God. The world that God made has deep harmonies because it was made by him and expresses him. In the Word, the wisdom of God, physical order (the positron) and mathematics hold together in harmony. Antimatter exists because it reflects within nature