He says the ice will cool the phototubes, making them more sensitive, and also provide an environment free of natural radioactivity.
In 1905 Thomson discovered the natural radioactivity of potassium.
In 1904, Nature published a study on the natural radioactivity of different mineral waters.
Uranium, thorium, and potassium are the main elements contributing to natural terrestrial radioactivity.
Any natural radioactivity strong enough to do that would be detectable from Xerxes.
Potassium-40 is the largest source of natural radioactivity in animals and humans.
I have only the natural radioactivity of the region to work with.
Shales and clays are responsible for most natural radioactivity, so gamma ray log often is a good indicator of such rocks.
Antineutrinos are another kind of antiparticle created by natural radioactivity (β decay).
What I am doing is to introduce a very gradual acceleration of the natural radioactivity in the Earth's crust.