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Do cosmic rays and the cosmic microwave background carry with them enough energy to have a macroscopic effect on events on Earth?

The most obvious example I can think of is by giving animals cancer. Maybe you can think of others. If they don't have a direct effect, maybe they can affect events indirectly via our Sun or upper atmosphere (butterfly effect)?

Therefore, if the stars were in different places or supernovae occurred at different times, would the history of life on Earth be completely different?

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    $\begingroup$ CMB ? unlikely ... cosmic rays ? why not ? Comets are better candidates $\endgroup$
    – user46925
    Commented Jan 19, 2016 at 2:55
  • $\begingroup$ I liked my original title, it was more poetic :P Also "causality" did seem like an appropriate tag. $\endgroup$
    – Varrick
    Commented Jan 19, 2016 at 3:09
  • $\begingroup$ what is the relation to causality ? you may edit it again $\endgroup$
    – user46925
    Commented Jan 19, 2016 at 3:13
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    $\begingroup$ Cancer: is that all that comes to mind when you think of mutations? Remember, evolution itself is seeded by genetic diversity. (A good biology question is how much comes from cosmic rays vs. copying errors.) Also, "causality" has a very particular meaning in physics. It is about the absolute limits for how abstract events can affect one another (often in the context of relativity). Something merely causing something else is... all of physics, really. $\endgroup$
    – user10851
    Commented Jan 19, 2016 at 3:21
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    $\begingroup$ arxiv.org/abs/astro-ph/0309415 $\endgroup$ Commented Jan 19, 2016 at 3:59

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There is an intriguing possibility that the answer is yes, in a very fundamental way!

All amino acids (except glycine) come in two chiralities, left-handed and right-handed, related by parity. However, all amino acids used in living beings are left-handed. Evidently, by chance, early in Earth's history, left-handed compounds gained an advantage somehow. Then this imbalance just grew, until they completely dominated right-handed compounds.

There are several competing theories on the origin of this imbalance. One proposed explanation was the weak force, which breaks parity symmetry, but its effect is tiny. A more recent hypothesis is that circularly polarized light from nearby nebula, which hit the early solar system, preferentially destroyed right-handed compounds and created the original imbalance. Thus, radiation from space may be responsible for the chirality of life on Earth.

This is a research topic, so nobody knows for sure if the hypothesis is true. If you want to read papers on it, the keyword is 'homochirality problem'.

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    $\begingroup$ There are many chiral-selective chemical reactions. Only physicists without knowledge of stereochemistry (a standard class if you want to be an organic chemist these days) will start looking for tiny effects when, in reality, there was probably an identifiable reaction step in some of the early biochemistry on earth which would have enforced that asymmetry. In general, before you trust physicists with chemistry, take a walk to the chemistry department and ask the chemists what they are thinking. Unlike us they actually know this stuff. $\endgroup$
    – CuriousOne
    Commented Jan 19, 2016 at 4:04
  • $\begingroup$ Strangely enough, most of the papers I found on this topic were in chemistry journals. I'll qualify the answer, though; in retrospect, the one paper that claimed that an initial, high imbalance was necessary probably was bunk. $\endgroup$
    – knzhou
    Commented Jan 19, 2016 at 4:12
  • $\begingroup$ Let me put it this way... if you had sent such a paper to me as the editor of a physics journal, I would have sent it back to you with exactly this comment without wasting even a minute on its content. If the chemists are willing to publish shoddy physics in their journals... that's their problem. Now, if you were given the physics task of finding a chirality breaking mechanism in your local environment, what would you be thinking of first... starlight or local magnetic field? When you ask this question from a chemist, would you expect them to have the right intuition? Me neither. $\endgroup$
    – CuriousOne
    Commented Jan 19, 2016 at 4:17
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    $\begingroup$ The big paper that founded this field, which inspired this answer, was published in Science and has a few hundred citations. And I looked at a lot more papers on this, also well-cited and in good journals, so I thought I was safe! $\endgroup$
    – knzhou
    Commented Jan 19, 2016 at 4:22
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    $\begingroup$ Are these papers wrong? Depends on your definition of wrong. For me this falls into the category of "intellectual nonsense" and "it's not even false". Yes, one can put out all kinds of hypotheses about what may have happened out there, but that's not science proper, unless someone has actually done a measurement of what really happened. Get me some measurements of exoplanet biospheres and we talk... until then I will tell the physicists to go to the chemistry department and take a class on stereochemistry (that includes the science peer reviewer who let it in). $\endgroup$
    – CuriousOne
    Commented Jan 19, 2016 at 4:34

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