Victor Hess

Victor Hess was an Austrian-American physicist who discovered cosmic rays through high-altitude balloon experiments. He shared the 1936 Nobel Prize in Physics for this discovery.

Cosmic rays: High-energy particles and atomic nuclei that travel through space and strike Earth’s atmosphere. Hess’s measurements established that penetrating radiation arrives from beyond Earth.
Atmospheric ionization: The creation of charged particles in the atmosphere when radiation removes electrons from atoms or molecules. Hess inferred radiation intensity from the ionization it produced in air.
Robert Millikan: An American experimental physicist known for measuring the electron’s charge and studying cosmic rays. Millikan developed influential early interpretations of the radiation Hess had discovered.
1912 Austrian balloon flight: Victor Hess’s 1912 balloon ascent that measured atmospheric ionization up to about 5,300 meters. This flight produced the decisive observation that ionization increased at great altitude.
Electroscope: An instrument that detects electric charge by measuring the divergence of charged leaves or a needle. Hess used electroscopes to measure air’s ionization during his flights.
Altitude: The vertical distance of a place or object above a reference level, commonly sea level. Ionization rose at high altitudes, contradicting a purely terrestrial source.
Werner Kolhörster: A German physicist who made high-altitude measurements of penetrating radiation after Hess’s balloon flights. Kolhörster extended the altitude measurements that supported Hess’s conclusion.
Nobel Prize in Physics 1936: The 1936 Nobel Prize in Physics, awarded to Victor Hess and Carl David Anderson. The award recognized Hess’s discovery of cosmic radiation and Anderson’s discovery of the positron.
Ionizing radiation: Radiation with enough energy to remove electrons from atoms or molecules. The radiation Hess tracked was identified through its ability to ionize air.
Absorption of radiation: The transfer of energy from radiation to matter as it passes through a material. The changing atmospheric thickness helped explain why radiation levels varied with height.

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Gamma-ray astronomyRelated: His discovery of cosmic rays helped establish the broader high-energy astronomy whose gamma-ray branch followed.