Supernova explosions provide us with spectacular displays, but have they done more for us other than some stellar fireworks?
Well the answer is yes! Life on Earth, and presumably life elsewhere in the Universe, does not remain the same over time - instead it evolves new forms, and supernovae are involved. Evolution occurs because within a particular species different organisms have different rates of success in producing offspring. The struggle for reproductive success promotes the characteristics of the more successful organisms. As a result, the characteristics of the organisms successful at reproduction will eventually become those of the species as a whole, which we may call a new species if those characteristics differ significantly from the original ones.
But what makes one organism within a species different from others? The answer lies with random genetic mutations of an organism. Most mutations are far from being helpful to an organism’s success at survival and reproduction, and so are generally harmful to a species so these ‘bad’ mutants quickly vanish from the scene. However, some mutations provide characteristics that help the organism to survive and reproduce. If these are inheritable, the ‘mutant’ will have many offspring, and so will their descendants until the ‘mutant’ becomes representative of a new species.
So what causes these random mutations? Well, no one knows for certain, but the answer includes such causes as genetic predisposition, trauma or chemical reactions. But it seems likely to be ‘cosmic rays' which is actually a misnomer because they are electrons protons and other nuclei that travel through space at nearly the speed of light. These fast moving nuclei continuously bombard the Earth and the rest of the Universe. Most of them pass through an organism when they encounter it, but it appears likely that some of the cosmic ray particles may sometimes strike the genetic material and alter it slightly, and so producing a mutation. If this is so, cosmic ray particles are a driving force behind evolution on Earth and everywhere else in the Universe.
And what produces cosmic rays? The solution appears to be supernova explosions, although some particles may be accelerated to near light velocities in interstellar space. The outermost layers of a supernova, blown into space at the highest velocities, may become cosmic ray particles, travelling through interstellar space. The bulk of the supernova explosion emerges at far more modest velocities, and eventually merges with other interstellar gas, enriching it in elements heavier than helium. But the fastest moving particles speed on their random ways until they encounter something to stop them, perhaps an interstellar atom, perhaps a star, perhaps one of us. Thus the relationship of supernovae and the evolution of life on Earth appears to be straight forward - supernovae make cosmic rays ray particles; cosmic ray particle impacts produce mutations; mutations drive evolution!
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