= Domenico Pacini
{c}
{tag=Physicist}
{title2=1878–1934}
{wiki}
= D. Pacini
{c}
{synonym}
<Domenico Pacini> tested the origin of atmospheric ionizing radiation by placing a sealed measuring instrument below the surface of <water>. His experiments compared the rate of discharge near the surface with that measured underwater.
A lower discharge rate underwater showed that part of the ionization came from radiation attenuated by the overlying <water>. Instrumental leakage and radiation from surrounding material also had to be considered. The result challenged explanations assigning all the penetrating radiation to local terrestrial sources, using shielding rather than altitude as the controlled comparison.<La radiazione penetrante alla superficie ed in seno alle acque by Domenico Pacini>[Original 1912 report in translation: surface and underwater measurements, residual ionization and interpretation]{ref}
\Image[https://commons.wikimedia.org/wiki/Special:Redirect/file/NCPaciniPicture2.png?width=260]
{title=Portrait of <Domenico Pacini>}
{description=Pacini family, 25 April 1920. Public domain (PD-anon-70-EU). https://commons.wikimedia.org/wiki/File:NCPaciniPicture2.png#Licensing[Source usage terms], via Wikimedia Commons.}
{source=https://commons.wikimedia.org/wiki/File:NCPaciniPicture2.png}
{width=260}
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