Aims of this episode:

  • Identify sources of background radiation;
  • Describe the three main types of radiation;
  • Explain how your location can affect the level of background radiation;
  • Explain how avalanches are formed.


Firstly, you need to understand that radiation is all around us. Right now, as you sit wherever reading this, tiny particles or waves of radiation are hitting you, some stop inside your body and damage the DNA in a cell whilst some pass straight through you and keep going. This ‘background radiation‘ does not cause you any lasting harm – we receive it in such small doses that it can’t do any lasting harm.

The background radiation comes from a variety of sources, these include the rocks around you and under your feet (Radon Gas), space (Cosmic Radiation), food, other humans, medical sources and finally (making up less than 1% of your background dose of radiation) nuclear experimentation (bombs and the like).

There are three main types of radiation:


This is made of 2 protons and 2 neutrons (the more observant among you will recognise this as the nucleus of a Helium atom). This is a pretty big particle and moves relatively slowly, meaning it is easily stopped. When a particle of radiation is stopped it ionises another atom, so Alpha is highly ionising.

Alpha is weakly penetrating – it won’t pass through much: 2 cm of air, some card or the first layer of your skin are enough to stop it. This means that from outside your body Alpha is the least dangerous, but if the material giving off Alpha Radiation gets inside your body… well let’s just say it never ends well. Click here for more.


This is just 1 lonely electron. Being much smaller and faster, Beta has an average ionising power and will require 50 cm of air or 5 mm of Aluminium to stop it. This is the most dangerous form of radiation if directed at you from outside your body since the thickness of the human body is usually enough to stop it.


Gamma Radiation is a wave, so has no mass and moves at the speed of light since it is light (part of the EM Spectrum). Therefore, Gamma is weakly ionising and will pass through a lot of material (up to 30 cm of Lead) before coming to a stop, meaning it is highly penetrating. This is a good thing for us as most of it will pass straight through your body without damaging it.

If you want to learn more about background radiation and the danger to humans, here’s our favourite radiation video.


Well, who knew you should be afraid of snow?

Check this out.

S@S 012: Radiation and Avalanches
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