Project F.A.B

Victor Hess and F.A.B

March 18, 2017 | 2 Minute Read

About now I expected to be home, dry and (hopefully) celebrating a successful launch. Unfortunately the weather conspired against us, so I - like my team - wait another week impatiently. In the quiet of the evening, and at the end of UK Science Week, I’d like to start a series of articles about scientists whose work had a direct influence on F.A.B.

The first of these scientists is Austrian born Nobel Laureate, Victor Francis Hess. Hess was born on June 24th 1883, and died on December 17th 1964. He died a US citizen, having fled there shortly before WWII with his wife - Marie Breisky - who was Jewish. In 1936 he was awarded the Nobel Prize for Physics in recognition of his discovery of cosmic rays. It is that work that gave the spark that grew into F.A.B.

Before we understand his work, we must first have a look at radiation and ionisation. To put it simply, radiation can mean two things, light (visible, radio, infra-red etc.) or moving sub-atomic particles (electrons, protons etc.). This is a fairly incomplete description but will fit our purposes.

To think of ionisation, consider an atom. It is made up of a positively charged nucleus, and negatively charged electrons that orbit the nucleus. If radiation strikes the atom, it will give the electron energy. If this energy is large enough, the electron can break out of the atom, overcoming the electrostatic attraction between it and the nucleus. This process of releasing the electron from the atom is ionisation.

At the time of Hess’ work (between 1911 and 1913) people assumed that the Earth was emitting radiation that was ionising atoms within the atmosphere. This would suggest then that the levels of ionisation in the atmosphere would decrease the higher above the ground one went. Hess decided to test this theory personally, by taking measurements of ionisation levels aboard nothing but a balloon.

Combining data from a series of flights during the day, night and even during a solar eclipse, Hess discovered what we now call Cosmic Rays. He reached his conclusion by noting that ionisation increased with altitude, contrary to the expected decrease. He found this to be the case both at night and during the eclipse. The sun was not the source of the radiation, it had to be coming from deep space - cosmic rays.

So he measured cosmic rays in a balloon - sound familiar to anyone?