# Are neutrinos diffused or defracted by the moon?

We all know that neutrinos pass directly through things, even big things such as the earth.

However it is also known that neutrinos interact with matter as a result of the Z boson or neutral current. This results in small amounts of momentum transfer and people have looked at whether this is measurable, e.g. by making neutrinos bounce off things that they hit at a very shallow angle.

If matter deflects neutrinos in this way then does this mean that neutrinos that pass through, for example, the moon will get very slightly deflected, probably in random directions, such that the moon ends up acting as a neutrino diffuser. Alternatively if there are internal density gradients then there might be a degree of diffraction. This will mean that if you are far enough away the moon will cast a neutrino shadow. Is the earth/moon distance sufficiently far away such that we are in a solar neutrino shadow during a total eclipse?

No one seems to have considered this possibility, but it seems not unreasonable, and possibly testable if this Augusts eclipse just happens to pass over a suitable detector

• You must not forget that the time in between solar neutrino detections is of the order of days even for the biggest detectors. Therefore a solar eclipse lasting only several minutes would not provide any good statistics. It may well be that the moon has some tiny impact at neutrinos but measuring it is going to be almost impossible. – gertian Apr 20 '17 at 9:09
• I was aware that this was probably the case; I was hoping that there was some recent improvement in the detection rate which someone was aware of. I would nevertheless still be interested in thoughts on the theoretical question of whether there is likely to be an impact on neutrino flux. – Nigel Dyer Apr 20 '17 at 9:44
• Not that I know of... As for the theoretical aspect, obviously some neutrinos will interact with the moon but this will be entirely negligible. As a "proof" you should look up the pictures that Kamiokande made from the sun trough the earth. There was no distortion of the picture whatsoever apart from the usual bad resolution of a neutrino detector. – gertian Apr 20 '17 at 9:52
• @CosmasZachos, they are not about neutrinos. – Helen - down with PCorrectness Apr 20 '17 at 17:03
• @Helen Oops! thank you... In fact, neutrinos going through the earth in these experiments ("earth shadow"?) might be a better handle. Looks like a really tough one.... – Cosmas Zachos Apr 20 '17 at 19:02

Another related question was answered by @dmckee here and gives an expression for the fraction of neutrinos absorbed by the planet Venus as $3\times10^{-8}$.
Now we'd expect the moon to absorb a smaller proportion (maybe $\frac 1 {16}$th of that), but we can use that as a rough guide and we see that the "shadow" would be barely perceptible even if we could detect most neutrinos (which we can't).