Thought of the Day... Speed of Light

The speed of light actually varies depending on the medium that it is travelling through. The accepted (and well known) speed of 186 000 miles per second - is actually the speed registered when travelling through a vacuum!

During tests it has been demonstrated that it can actually travel a lot slower. In one test in which it was directed through Sodium which had been frozen to almost 'absolute zero' - it was recorded as travelling at 38 miles per hour.