If you put a giant mirror far out into space could you see into the past by observing the mirror?

Answer 1

Theoretically you could, but don't go shopping for giant mirrors any time soon. You might be thinking that if we place a large enough mirror far enough away that we could somehow see into our own past-- that is, the past relative to the people placing the mirror. In order for us to see our own past in the mirror, the mirror must already have been put in place at an enormous distance long, long ago, so that the light we see reflected in the mirror will have had its origin on earth at the distant past time that we would like to observe. Not doable. However, theoretical physicists and other scientists are already outlining not-totally-outlandish scenarios where travel through time may be possible in some circumstances. The outlining and the necessary engineering are probably going to be separated by many generations before there is any practical demonstration. Much more useful is the reality that the light we now observe from distant stars started its journey from the star as long ago as millions or even billions of years. Interestingly, from the point of view of the photons themselves, the trip is instantaneous.

Answer 2

Your eyes would explode.

I'm kidding, of course. You'd see a mirror through a telescope (or, more likely, you'd see whatever was being reflected in that mirror through the telescope). What did you expect would happen?

Answer 3

No, placing a giant mirror far out into space would not allow you to see into the past. The reflection you observe in the mirror would still be in real-time since light travels at a finite speed, so you would only see events that happened at the same time as if you were observing them directly.