What is anti-matter?
To understand what anti-matter is, we must first look at what matter is. Matter is anything that has a mass, it contains atoms which themselves are made up of protons, neutrons and electrons. The centre of an atom, known as the nucleus contains positively charged protons and neutrally charged neutrons, these are held together by particles known as mesons. The electrons in the atom are negatively charged and orbit the nucleus.
Antimatter in the other hand is the opposite of matter; it consists of positrons (positively charge electrons) antiprotons and antineutrons. Both particles and antiparticles have the same mass but consist opposite charges.
Who predicted it and why should there be such a thing?
The existence of antimatter was predicted by Paul Dirac who was an English physicist (1902-1984) and was described to be the best British theorist after Sir Isaac Newton. The research he did was rather more ‘predicted’ as it was not based on scientific evidence but his methods were based on theory. Dirac constructed a theory by combining quantum mechanics (which described the subatomic world) and Einstein’s theory of special relativity (which states than nothing can exceed the speed of light). The theory and equation he made described how objects that are both miniscule and fast like electrons behave. He found out that his equation works not only for electrons that are negatively charged, but also for electrons that were positively charged, out of this he predicted the existence of antiparticles. Dirac then suggested that there may be an entire other universe consisting of antiparticles where all particles have an opposite charge to the particles in this universe.
How was it discovered?
Anti-matter was already thought to have existed thanks to the work of Paul Dirac; unfortunately it wasn’t discovered until another 6 years later after Dirac proposed his theory. Another scientist named Carl Anderson (as seen on the right) managed to gather evidence from a photograph which proved the existence of antimatter. This came about due to another scientist known as Victor Hess discovering cosmic rays. Anderson designed and built his own cloud chamber (a device used to identify particles) which he used to examine the cosmic rays. He noticed that there were positive and negative particles. What was most intriguing was that the mass of the positive particles was less than that of protons. In order to prove that these were not merely negatively charged electrons moving in a different direction he decided to insert a lead plate into the chamber and take a photograph of it. In the photograph an electron can be seen hitting the plate from the bottom. After it hits the plate it looses energy yet still carries on in the direction that a positively charged electron (positron) would go, thus the discovery of antimatter.
What happens to anti-matter in the world of “matter”?
It is believed that when matter and antimatter collide, they are both annihilated as they cancel each other out and an enormous amount of energy is created. It makes sense that when the big bang occurred, large volumes of matter and antimatter collided producing the huge ‘bang’ but it is not clear why there is an excess of matter left in the universe as it would make more sense to believe that they exist in equal amounts.
Bibliography
https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjyevyDVDmIrcjf6LXpzOd1goLC1JpH8xvKkp8-TO7m1n-U08tFrsRlQNpaSurjd5wOhFftzD0aMBNYJ38SH9RsMbqnI4jjbb1qJj-5Wqvhu7CX4_xnFLho-8fSrQBRv3EgQugyrmtSTt0/s1600/antimatter.gif (Hydrogen/Anti-Hydrogen figure) 16/02/20011
http://www.aps.org/programs/outreach/history/historicsites/anderson.cfm (Carl Anderson figure also taken from this webpage) 16/02/2011
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