Outer space is not exactly a friendly environment, which is why we go through great lengths before we boost people up there. Once you get a few hundred kilometers away from our beloved rocky planet things get uncomfortable due to the lack of oxygen, extreme cold, and high doses of radiation.
Especially the latter poses a great challenge for long-term space travel, and so people are working on various concepts to protect astronauts’ DNA from being smashed by cosmic rays. This has become ever more salient as NASA contemplates future manned missions to the Moon and Mars. So let’s learn more about the dangers posed by galactic cosmic rays and solar flares.
Radiation from Space
When German Jesuit priest and physicist Theodor Wulf climbed the Eiffel Tower in 1910 with an electrometer he wanted to show that natural sources of ionizing radiation are originating from the ground. And while readings on top of the tower were lower than the ground level, they were still much higher than would be expected if the ground were the only source. A few years later, Victor Hess undertook several risky balloon flights up to altitudes of 5.3 km to systematically measure the radiation level by observing the discharge rate of an electroscope. His experiments showed that radiation levels increase above ~1 km, and he correctly concluded that there must be some source of radiation penetrating the atmosphere from outer space.
The cosmic rays that rain down on Earth are predominantly protons (~90%), helium nuclei (~9%), and electrons (~1%). In addition, there is a small fraction of heavier nuclei and a tiny whiff of antimatter. These particles are blasted to us from the Sun and other galactic and extragalactic natural particle accelerators like supernovae or black holes.
