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Super Reflecto Vision!!

Henningjohnathan

18:22 / 16.05.06

Is this theoretically sound?

Lets say 6 billion light years away there is a celestial body covered with reflective surfaces or substances. The light reflected off that body and striking earth directly would be 6 billion years old, correct? However, if we were able to take an extremely detailed photograph of this 6 billion year old object and look into its reflective surface like a mirror, wouldn't we in fact see a starry sky that was even millions or billions of years older?

matthew.

18:26 / 16.05.06

As I understand, looking at the curvature of space allows you to see the curvature of time, seeing as how they are linked. Really when we see the sky right this second, we see the sky as it was in the past. The further you go, the farther into the past.

So, if you looked at something reflective in the distance, that the something is already in the past. What is being reflected is in the past relative to the present of the something. Therefore, I don't see why you couldn't multiply that into your theory.

But I'm no astrophysicist. I have an English degree.

Henningjohnathan

19:16 / 16.05.06

It sounds sensible, but the farther back you go the stranger it seems to me.

When did visible light appear in the universe? From the very beginning? What did it shine in/upon? If the universe is 13 billion years old and therefore has a 26 billion light year radius, then if we look back at a silver asteroid or planet 5 billion light years away, it would look like it did when the universe was 7 billion years old and had a 14 billion light year diameter.

HOWEVER, the night sky reflected in the surface of the silver world could have light from the very first few moments of space.

In fact, if we look to the farthest edges of visible space, in any direction, wouldn't we actually be looking back at the very first moment of the universe when it had a diameter of practically zero?

yami

19:50 / 16.05.06

Yes - and if we found a sufficiently bright, coherent radio reflector near Alpha Centauri, we could point our telescopes at it and recover news reports from c. 1997. Mirrorlike surfaces are hard to come by naturally (most high-albedo planetary surfaces are more like snow, very reflective, but you can't use it as a mirror) but once you assume a giant space mirror, you're set.

In fact, if we look to the farthest edges of visible space, in any direction, wouldn't we actually be looking back at the very first moment of the universe when it had a diameter of practically zero?

Not quite the first moment - there was an earlier period of time when light couldn't travel very far without being absorbed by a particle soup - but pretty close. Observations of the cosmic background radiation are the basis for theories about the universe's earliest evolution.

Henningjohnathan

21:02 / 16.05.06

What about an ocean as a reflective surface? Could the Earth have been used a few billion years ago as a mirror for a distant but very advanced race of extraterrestrial astronomers?

yami

05:41 / 17.05.06

I find reflective stargazing on a calm lake very difficult, so I don't imagine that the ocean would be a good space mirror. Clouds, waves, plankton, atmospheric distortion, scattering from interstellar dust, etc - all this might introduce unrepairable fuzziness, but then again maybe the aliens have super-duper adaptive optics, or some advanced technology sufficiently indistinguishable from magic.

The real question is, what would such a civilization gain from using Earth as a mirror? Anyone who wants to see the early universe can do so by looking directly at far-away objects; unless you have an interest in the evolution of one particular reflected system, I'm not sure reflection astronomy would be worth the trouble.

Quantum

02:12 / 13.07.06

Scattering.

Even with an optically perfect mirror through a medium which didn't scatter (i.e. a perfect vacuum, which as far as I know is impossible never mind the state of outer space) just consider for a moment how big a telescope you'd need. You're talking about discerning images that at best are a light year there and back. Weather satellite Geostationary orbit is roughly 22,222 miles, a light year is 5,878,482,084,580 miles or so. So for an accuracy of one one-thousandth of a weather satellite (so you could just about see the earth as a dot) you would need a telescope over 5,000,000,000 times as good as that*.
Theoretically speaking, there are many factors you haven't considered. Perhaps it's best to leave it at that.

Here's some info on the Hubble space telescope you might be interested in.

*6 thousand billion miles times two (there and back)=12 thousand billion, divided by 22= 545 billion.

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