How Long Does Light Live?

Most recent answer: 06/18/2013

How long does light "live"? That is, was the light that was "on"/visible on the Earth 1,000,000 million years ago still around now? Are light rays--electromagnetic energy--eternal, or do they "die" somehow?
- Mona Morstein (age 52)
Mesa, AZ, USA

If a particle of light, called a photon, doesn't bump into anything and get absorbed it just keeps on going forever.  Astronomers have observed light from stars that has been travelling for 10 billion years or so.  Mind boggling. 


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This is what the night sky looked like 13 billion years ago.  See


That light hasn't "died" since but it has reduced energy due to the stretching of the universe.  Mike W.

(published on 06/18/2013)

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