Neutrinos have no mass and no charge. Therefore, they are not deflected by the other particles in our body and pass through us. Photons too have no mass and no charge, but why are they being deflected then?
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4$\begingroup$ But the photon mediates the electromagnetic force, it's a force carrier. $\endgroup$– snultyCommented Dec 15, 2016 at 16:47
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21$\begingroup$ Neutrinos do have mass. $\endgroup$– Jon CusterCommented Dec 15, 2016 at 16:50
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15$\begingroup$ Also interesting to note that neutrinos do interact with us, just rarely. Avoid being close to supernovae and you should be fine. $\endgroup$– Dan BryantCommented Dec 15, 2016 at 22:50
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$\begingroup$ Neutrinos are not gauge quanta (they're fermions) while photons are, i.e., photons mediate the electromagnetic interaction and as such, are spin 1 gauge quanta that interact with electrically charged particles. $\endgroup$– Alfred CentauriCommented Dec 17, 2016 at 4:43
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3 Answers
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Light rays are a combination of oscillating electric and magnetic fields, and both fields interact strongly with charged particles. That's why light rays are strongly scattered by matter. The relationship between light rays and photons is more complicated than you might think, but this also explains why photons scatter off charged matter even though the photon has no charge.
By contrast a neutrino only interacts via the weak force. It's a little misleading to say this is a weak force - we should rather say it's a very short range force. Either way, for a neutrino to interact with electrons or nuclei is many orders of magnitude less probable than for a photon to interact.
answered Dec 15, 2016 at 16:54
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16$\begingroup$ You might also point out that lots of photons don't interact with the human body. Radio waves and X-Rays mostly pass right through us. $\endgroup$ Commented Dec 15, 2016 at 19:42
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3$\begingroup$ @Shufflepants If we are super nit-picky, it's worth of mentioning that "lots" is misleading, as this has very little to do with the amount. You can easily have lots of photons interacting, just need to pick the correct wavelength. I'd even say that lots of xray do interact with human body, enough to produce useful pictures. Sorry if I come by as snarky, but I don't like mixing up effects related to frequency of photons with the ones related to actual amount of them. Too many people cannot actually differentiate the two. $\endgroup$– luk32Commented Dec 16, 2016 at 0:38
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$\begingroup$ Still it depends entirely on the wave length if a photon will interact with a given matter or not. $\endgroup$ Commented Dec 16, 2016 at 9:14
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$\begingroup$ @luk32 He was talking about the wavelength. And since the typical absorption (and more importantly for imaging, scattering) rate of X-Rays in human body is much lower than 50%, I'd say that "mostly pass right through us" is entirely appropriate. $\endgroup$– LuaanCommented Dec 16, 2016 at 10:21
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$\begingroup$ I was talking about wavelength and quantity. Below a certain wavelength and above another certain wavelength more than 50% of photons incident to your body will pass completely through it. As the wavelength decreases in the first case and increases in the second case, the proportion of photons that go through your body without interacting goes up (on the average, there may be slight dips at specific frequencies but the overall trend is up). $\endgroup$ Commented Dec 16, 2016 at 14:59
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Photons are electromagnetic radiation which means they interact with charged particles in our bodies. More energetic ones like x-ray and gamma rays do pass through while visible light mostly doesn't.
answered Dec 15, 2016 at 16:51
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wishing all a happy holiday ! Neutrinos belong to the Leptons, where as photons are a boson, as stated above they are a force carrier...! Due to their extremely small size, or perhaps some other "hidden variable", neutrinos interact weakly.... https://www.mpi-hd.mpg.de/manitop/StandardModel/pics/standard_model_elementary_particles.png
