About light in the universe?
2017-07-17 8:53 am
As a light source in the universe (e.g. sun) emit light to different directions, some of the light emitted reach places like earth, and some don't. So do the light that reach the earth disappear or it is reflected to other different directions? And for the light that didn't reach any place, do they keep on going forever? If they do keep on going forever, will the universe become brighter and brighter? Thanks!
回答 (2)
2017-07-17 9:18 am
Basically, a photon travels forever unless it's absorbed or reflected; in some cases, it's path is 'bent' around gravitational sources...
It's important to know you can't *see* the light unless it goes to your eye; but if there's no other objects to reflect that light to your eye - the universe will get no brighter than it already is...
It's important to know you can't *see* the light unless it goes to your eye; but if there's no other objects to reflect that light to your eye - the universe will get no brighter than it already is...
2017-07-17 11:38 am
Some light is reflected, some is absorbed, some is absorbed and re-emitted at a different wavelength, and if it strikes nothing it goes on for ever.
The Universe can only become brighter if the light is reflected by something back to your eyes. Unless it enters your eyes you cannot detect it. Otherwise your eyes would be useless, since everything would be just a glare.
See also "Olber's Paradox".
The Universe can only become brighter if the light is reflected by something back to your eyes. Unless it enters your eyes you cannot detect it. Otherwise your eyes would be useless, since everything would be just a glare.
See also "Olber's Paradox".
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