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Last Post 19 Mar 2019 08:39 AM by  Kris Sigsbee
Neutrinos (TW)
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Hal
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19 Mar 2019 06:43 AM
    @SolarWeek - How do we know that neutrinos streaming from our sun ☀️ outward in all directions from observers on earth 🌎 aren’t what’s causing red-shifting of the inbound starlight of distant galaxies? (as opposed to our current Big Bang interpretion?)
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    19 Mar 2019 08:39 AM
    Hello! This is a rather odd question. I'm not quite sure where you would have heard that neutrinos cause red-shifts. Perhaps you have misunderstood what a neutrino is, and what a red-shift means?

    Neutrinos are elementary particles that interact with matter only through the weak subatomic force and gravity. Neutrinos are electrically neutral and are so very tiny that their rest mass was thought to be zero for a very long time. Neutrinos are produced by radioactive decay, or in the cores of stars like our Sun, or in supernovas, or by cosmic rays striking atoms. Neutrinos can also be produced artificially by nuclear reactors, nuclear bombs, or particle accelerators. Most of the neutrinos we find near the Earth come from nuclear reactions in the Sun. Here on Earth, about 65 billion solar neutrinos per second pass through every square centimeter.

    Red-shifting is completely unrelated to neutrinos. Red-shifting refers to the phenomenon where electromagnetic radiation (such as light) from an object undergoes an increase in wavelength, equivalent to a decrease in wave frequency and photon energy, thus shifting the spectrum of the radiation. Although the term red-shift implies the shifting of visible light from blue to red, the electromagnetic radiation does not need to be in the visible part of the spectrum. An example of red-shifting would be visible light from a source moving further away perceived by a very distant observer as radio waves. The opposite of a redshift is a blueshift, where wavelengths shorten and energy increases.

    There are three main causes of red shifts in astronomy:
    1) The Doppler effect caused by objects moving apart in space.
    2) The cosmological redshift (Hubble's Law) caused by space itself expanding, causing objects to become separated even though they have not changed their relative positions. All distant light sources more than a few million light years away show red-shift consistent with the rate of increase in their distance from Earth.
    3) Gravitational red-shift, which is a relativistic effect caused by extremely strong gravitational fields that can distort spacetime.

    So red-shifts and neutrinos come from completely different physical processes, and do not cause one another.
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