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I wonder if there is research into gravitational lenses or other possible sources of naturally occuring space mirrors or lenses that we could use to collect lig
by ignifero 15y ago
I wonder if there is research into gravitational lenses or other possible sources of naturally occuring space mirrors or lenses that we could use to collect light rays from the earth's past, maybe to detect its spectral content.
- hugh3 15y agoThere isn't any research, but only cuz it's damn impossible. The number of photons ever emitted by Earth in the distant past which are gonna ever come back to Earth is... very very small.
- ignifero 15y agoYet, since there are not many similar atmospheres in the region, if there were any backscattered radiation it wouldn't be impossible to detect.
- nikcub 15y agothis idea reminds me of how during the cold war the US military used the moon as a reflector to measure USSR air-defense radio signatures. they were able to determine the capabilities (range, frequencies etc.) of USSR air defense without ever entering the air space. you would assume that light from earth is reflected back from objects in deep space. the problem would be sorting out all of the weak signals and finding what you are looking for by calculating where the reflection would end up and going out and finding it. the signal would likely be too weak to interpret with today's technology, but in theory it would be possible. (another theory is with light being bent by gravity it is possible that light from earth has been bent back around to pointing back to us (ie. around a black hole). we just don't know how to find it or where to look)