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Asked by to Kieren, Rowena, Roy on 19 Mar 2014. This question was also asked by .
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Rowena Fletcher-Wood answered on 19 Mar 2014:
E = mc^2
Einstein’s special relativity is a theory that links mass and energy – they are equivalent or convertable. That means that there must be a critical energy belonging to a massless but still existing thing like light. I guess the equation must therefore be a limit which mostly works like an equation, but staring at it now it doesn’t seem to make mathematical sense. I guess relativity is just like that…
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Kieren Bradley answered on 20 Mar 2014:
There are some lovely equations called the Maxwell equations. They show that light is made up of a magnetic field (the one you can usually see when you put iron filings on a piece of paper above a magnet) and an electric field (the thing that makes your hair go all static if you stand close to a van de graph generator). When the fields (think of them as arrows going between north and south poles, or positive and negative electric charges) constantly change direction they can start moving forwards (get a slinky or a rope and wiggle it side to side and it will look like the waves you create move forwards) but the only speed at which they can move forwards without the fields disappearing is at a speed of 300000000 meters per second which happens to be the speed of light.
This is only the speed of light in a vacuum, if the light goes through a material like water or just air it will be slowed down by the fact there are atoms that it bumps into. Some scientists have shone light through very cold sodium atoms have got light to go at just 38 mph.
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chocolatebuttons commented on :
Thank you both