Looking back in time?

Question

When we look at the cosmos we are looking back in time becuase light takes time to travel a distance. What if we were to place a mirror 1 light year away, looking into it and seeing our reflection we would be seeing ourselves as we were 2 years earlier. Theoretically, could you do this at different distances and see different stages of the earth? Is there some object that could exist that is reflecting the light from earth that could allow us to actually view it being formed?

Large masses also cause light to bend, what if our light has bent around some distant object and we can see our Earth as it once was?

Answer 1

The amount of light reflected by the earth is too little to make it very far.
Even with stars, the unaided eye in the night sky only sees about 2,000 stars, despite there being over 200 Billion in the Milky Way alone.

Answer 2

This answer is obviously gonna be tricky, but I'll try to keep my answer as short & simple as possible...

If it were possible to travel faster than the speed of light, then yes, you could look back at the Earth and see the past. Just placing a mirror the distance of 1 light-year away doesn't mean we would see a reflection of 2 years earlier...you, the viewer, would have to travel faster than the speed of light in order to look back in time.

As for an object reflecting light, I guess it could exist. That's actually a rather deep philosophical question in its own right...the theory being that... if you look at a room full of people, you can tell who is in the room, but you can never be 100% certain that somebody isn't there - maybe you just haven't seen them yet. So, I doubt some huge mirror exists that would allow us to see back in time, but you can't ever be 100% sure that something doesn't exist - maybe it's out there and we just haven't found it yet.

Answer 3

The Earth is about 4 billion years old. To see Young Earth, you'd need a "mirror" in position over 4 billion light years away so that the reflective surface would send back those first photons that bounced off of Young Earth's surface. It would take another 4 billion years to get here. Unfortunately, by that time the Sun will have become a red giant, swelling so big that it will grow into the Earth's orbit. Humankind will be long gone from this planet by that time.

Answer 4

The theory is great if you can get around light speed. To see Ancient Egypt in action you would not only have incredibly sensitive equipment, you would have to place the mirror 2000 light years away. Then wait another 2000 years for the light to get back.

However, the idea has been used in science fiction. The good guys placed a camera 3 light years from the bad guy's planet to know what happened 3 years ago. Of course, they could teleport stuff.

Answer 5

If the mirror or object was in place already for the light from us to hit it, then yes, theoretically it would be possible. However, there is no way to catch up to that light beam sent out at the birth of our planet and theoretically still traveling today.

Answer 6

One of the problems with the idea that humans will ever travel at the speed of light is a little problem called the Loretz-FitzGerald contraction. Light travels at about one foot per nonsecond (billionth of a second). As one approaches that speed one begins to be compressed or contracted in the direction of travel. This kills the travler. Not a good thing.

Answer 7

Theoretically, yes, that's possible. However, it would have to be half the age of the earth away in light distance. Further, for it to continue being useful, it needs to be moving at .5c.

Answer 8

No, beacause the mirror wasn't there in the past! It's like the old paradox of time travel: What would would happen if you traveled to the time before the (time) machine was created?

Answer 9

I've read that Quasars could be radiating light that they receive back to the source. That is probably the direction you would want to take your search.

Answer 10

this is interesting