I’ve seen many videos on the topic, but none seem to answer the question, How do we know there are trillions of neutrinos passing through our body when we have a really hard time detecting them. Why do we say there are so many of them when we cannot prove it?
In: Physics
Usually when we look for subatomic particles, we already know what we’re looking for before we check. No one built a particle detector, switched it on, and suddenly found neutrinos. We predicted the existence of neutrinos based on our other physics models, and then we built detectors after the fact to see if we were right.
We looked at the sun, and noted that some particular reactions that are going on inside should be making neutrinos. Given the size of the sun, we can estimate how many are made. Given how far Earth is away, and how big Earth is, we can estimate how many reach us. And if we design a detector that can spot them, we can estimate how many the detector *should* spot. We then build that detector, switch it on, collect data, and see what we find. If we get the number we expected, it means our original hypotheses were likely correct. If not, it means we have to revise our hypotheses until they can explain what we’re actually seeing.
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