Question

Fusion reactions in the Sun's core produce 2 x 10^38 neutrinos per second. If these solar neutrinos radiate isotropically away from the Sun, about how many solar neutrinos are inside your body at any given time? Is this larger or smaller than the number of neutrinos from the cosmic neutrino background that are inside your body at the same moment?

Answer 1

Using the inverse-square law, the number of solar nutrinos inside our bodies will be:

[since they are emitted over the entire solid angle of 4pi]

L = distance between Sun and Earth = 149.6 x 10⁹ m

assuming that the area covered by a human being is about 400 cm², the number of neutrinos inside our body at any given time will be:

.

This is many orders larger than the number of neutrinos from cosmic neutrino background.