Seeing Earth's past?

Question

I know there have been some questions from uneducated users who want to know whether or not, being on a distant planet, one could see Earth as it was in the past. Of course, light traveling to a distant body from Earth would have to take time to reach that body...

But my question is: with much advancement in telescoping, would it be possible to find a surface out in space somewhere, a perfect mirror as it were (created perhaps by an icy planet or a similar object) that reflects light perfectly enough to see our own light reflected back as it was however long ago?

I know that in order to reflect something as TINY as the Earth from the distances I'm speaking of, the object or planet surface may have to be impossibly smooth (perhaps even down to the level of its atomic arrangement?), and for all I know the resolution of a telescope could never be able to achieve something like this... just want to know if there's any possibility of it?

Answer 1

Resolution, (the ability to 'see' tiny images), is limited

by the wavelength of the light used.

Beyond a certain point, all you get is fuzz.

our astromnomical telescopes are already good enough to have come up against this limit.

Answer 2

Imagine that your mirror is already in place on a planet around a star which is 4 light years away.

The light hitting that mirror now left earth in 2004, and will bounce back to arrive in 2012. So yes, you would be looking at the past.

However, even if you could travel at the speed of light, and even if you had the mirror already ready to transport, you are not going to be able to see any light that left the earth before the time that you began your journey to deposit the mirror.

Whenever you look at yourself in your bathroom mirror, you see yourself not as you are, but as you used to be some small fraction of a second ago.

Answer 3

As a matter of fact your question makes sense since FTL (Faster-Than-Light) doesn't exist yet. A icy body that is reasonably smooth could reflect Earth's light rays. Unfortunately, there are also a few problems:

1. Perfectly reflective ice is impossible to create artificially,  much less naturally.

2. To look effectively at the past, the object would have to be many light years away.

3: The said object would have to have a large mass but a low density and no atmosphere.

4. Also, the said object would have to be stationary. In other words, it will have to not be in orbit around a star, but just floating out in isolated space. Besides, if it follows #3, then it might break up due to gravitational tidal forces if it comes close to another large body.

5. If an asteroid or comet was to collide with said object, then said object would shatter like a mirror, no pun intended.

6. Despite advances in telescope technology, at best one might be able to observe worldwide ice ages, volcanic eruptions, giant asteroid collisions, etc. Small, localized events, such as the Civil War, Super Bowl XXI, Blair Witch Trials, etc, would not be able to be seen.

7. Furthermore, this "galactic mirror" would have to be flat and non-rotating. This alone is impossible, because the 'mirror' would have small, stellar winds acting on it. These would cause it to rotate. At such a great distance, this would radically change the view. Also, gravity causes weightless objects to form into spheres. A spherical mirror would be fine if it weren't for the light distortion caused by convex (outward-pointing) mirrors.

8. Finally, light would get distorted by gravity, dark matter, and light pollution from stars near the reflected light.

All in all, while your theory is better than others, it is simply is impractical. Sorry.

Hope this helps.

Answer 4

possibilty, yes.

probability, probably about 1 in 10^100000000000000000000 against

Answer 5

In theory, if light could be reflected back to the Earth we would be able to see into the past; however, there is no device that could reflect it back so precisely for us to see it nor a telescope of sufficient resolution to image it.

Answer 6

You will never find any type of natural orbiting body in space that has that level of perfection for reflection....the odds say it is so.

I seriously doubt that you would find reflected light that will project the Earth's past so we could see it.

I will say that...it's a nice concept though...I wish it were so.

(no rhyming puns intended)....;))

Answer 7

Congratulations, Mandy! Great to see a truly innovative and provocative idea.

As others have pointed out, the technicalities of what you propose are enormous, but in theory your concept is valid and would be a way to look back and actually see history being made. I'm not an optics / telescope expert, but I'm wondering if some kind of interferometry might solve the resolution problems.

Answer 8

Only in the most hypothetical sort of way.

There is nothing in our solar system like that, of course.  So we would be talking about interstellar distances.  It takes an awful lot of technological supposing to meet the telescopic requirements.

But IF something like that existed, why would it be aimed toward us?  Everything moves and rotates.  In addition, the reflection would be dominated by the sun.  If you are asking for purely hypothetical reasons, then yes, if we could see such a reflection from a mirror 100 light years away, we would see earth as it was 200 years ago.