A number of scientific themes run through the recently released movie Angels & Demons. The popular, but misguided, notion of a perpetual conflict between science and religion (the Roman Catholic church in this instance) provides much of the narrative. Part of this conflict centers on a plot to blow up the Vatican with an antimatter bomb. Just a quarter of a gram (less than the mass of a paper clip) of antimatter making contact with ordinary matter would unleash an explosion similar to those produced by the atomic bombs used to end World War II.
The destructive potential of an antimatter bomb arises from its interaction with normal matter. Whenever a particle contacts its antiparticle, the two annihilate and convert their mass into pure energy. Einstein's famous equation, E = mc2, tells us that the energy released is the mass of the particles times the speed of light squared. Thus, a small bit of mass converts into an enormous amount of energy. Fortunately, everywhere scientists look in the cosmos, they see only matter. Even powerful and sophisticated telescopes detect only trace amounts of antimatter. While this lack of antimatter in the universe bodes well for life (typically the energy released comes in the form of x–rays and gamma rays), it poses a problem for understanding the cosmos.
Here's why. Scientists regularly make extremely small quantities of antimatter by colliding high–energy particles at accelerators like the Large Hadron Collider (LHC). Studies based on those collisions demonstrate that almost all known physical processes produce equal amounts of matter and antimatter. These same processes govern the universe back to the earliest moments after the big bang. So, how did those processes lead to a universe containing only matter? Where did all the antimatter go?
Particle physicists recognize some processes that generate slightly more matter than antimatter. In technical terms, those processes violate a symmetry known as "CP–symmetry". In a nutshell, a process obeys CP–symmetry if its results are identical after changing all particle positions to a mirror image and changing all particles to their antiparticles. CP–symmetry–violating processes can produce an excess of matter because they treat particles and antiparticles differently.
Cosmologists can explain the lack of antimatter in the universe if enough CP–symmetry violation occurred shortly after the big bang, resulting in more matter than antimatter. After the excess was produced and the universe cooled more, all the antimatter would have been annihilated with the normal matter, leaving a residue of matter and energy. Calculations show that it would take roughly one extra matter particle for every billion matter/antimatter pairs to generate the matter density of our universe.
One aspect of this explanation that troubles physicists is that the nature of the CP–symmetry violation seems unusual. In other words, its value differs from the theoretically expected value. If the symmetry–breaking were more in line with the expected value, the universe would contain too little matter for life to arise. This indicates fine–tuning in the amount of CP–symmetry violation.
However, fine–tuning implies an Agent external to the universe (that is, a supernatural Agent) was involved in its origin and development. Recent research, which I will discuss next week, reveals that the CP–symmetry violation fine–tuning may be "solved" given the masses of the most fundamental particles known to physicists: quarks. But this solution simply moves the fine–tuning to a different part of the model, namely the quark masses.
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