As I'm sure we all know, the light we see from a lot of the stars is old...now let's say in theory I could go to a star 50 million light years away...and view light reflecting off of the earth...would I, with the best telescopes available today, be able to see in any detail happenings on earth? If not with todays telescopes, does the reflected light have enough detail to show this?

I'm answering your "bottom question" from Spurious here, where it's supposed to be answered.

Of course the detail deterioates (sp?)! Do you see things just as well from 2 miles away as you do up close? All you see is reflected light.

Well you can either fly 50 million light years away and test your theory or you just ask an astronomer how much detail a star has that�s 50 million light years away and has approximately the size of earth.

And its not very much.

[This message has been edited by Dr Know (edited 08-28-2002).]

50 million light years is quite far away. It would be difficult to see any detail at all, of course this is light degradation the further you get away, but after even a few light years you would lose detail of the small inner planets. However you must be able to see some detail, because scientists can speculate on whether stars have planets and of what size, by the bulges gravity causes on the sides of the stars, but I think they do that on other spectrums of light then viable light.

Linhir

"If the radiance of a thousand suns
Were to burst at once into the sky
That would be like the splendor of the Mighty one --
I am become Death,
The shatterer of Worlds."
-Hindu Spiritual, Bhagavad Gita

Well, the light rays bouncing off the earth aren't all flying out in straight lines. They're spreading out in every direction as they get farther out. So, you'd have to have a lens as wide as a galaxy to catch all the rays that far out. Of course, that assumes that the light wasn't obstructed by planets, cosmic dust, etc.

Astronomers aren't able to actually see planets around other stars. They are able to infer them, from wobble, cyclic blocking of the light coming from them, spectroanalysis, ect. This is only possible for large, massive planets.

You need a certian sampling of the light coming from a place in order to get a detailed image. Thus the further away you are, the larger the telescope you will need. At those kinds of distances you could concivably get an acurate veiw with a gravity lens.

For those not framiliar with the concept of a gravity lens I will explain it.

Gravity bends light.
The sun bends light more or less evenly.
At some distance from the sun there will be a focal point of where the light was bent.
If you use a special second lens that blocks out the light from the sun itself you should get an extremly detailed veiw.