Where does the light go when I turn all the lights off and close the curtains?

10 Mar

You’re in a bright, well-lit room. But when the power goes out, where does all that lovely light that the room was so full of, go? It was wall-to-wall, floor-to-ceiling, a room packed with light. Sure, you’ve ceased production of new light, but the existing stuff can’t just disappear into thin air – after all, the first thing they teach you in physics is that energy can’t be destroyed. So what happens?

I’m going to try and explain this without getting too deep into particle physics – for the readers out there who think that Higgs-Boson is a firm of accountants and Brian Cox is still That Guy From D:Ream.

The simple answer is that light does not exist.

You will be aware that sound comes in waves.  These waves, like waves in your bathtub, react to each other.  Matching ones will merge and grow and splash over the edges, and opposite ones cancel each other out.  This is how noise-cancelling headphones work – they match the outside sound waves to cancel them out so your music is perfectly clear.  ‘Light’ is also made up of waves (and particles as well, but we’ll get to that later).

Current estimates suggest that around 70% of the universe consists of dark energy.  A further 25% is dark matter, and we are a tiny tiny proportion of the remainder.  Dark energy is all around us.

This is the technical bit:  What we perceive to be ‘light’ is actually dark energy waves cancelling each other out. If you look at the picture above and imagine an identical one, flipped and put on top, it creates a rounded bubble shape with no gaps.  This is the particle they refer to when describing light as both a particle and a wave. The Sun, light bulbs, glowsticks and fire are all sources that generate waves the same as those of dark energy, cancelling the dark out.  When they stop, so does our perception of light.

1 Comment

Posted by on March 10, 2012 in Silly, What?, Where?


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One response to “Where does the light go when I turn all the lights off and close the curtains?

  1. KK

    October 16, 2012 at 2:42 pm

    The light goes out on a date with dark and you will never see it again. sorry


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