Can slowed light be used to see the past?

Question

I read something about light being significantly slowed down. If a viewer was looking at the slowed light beams, would they see a delay from a certain event happening. P.S Im quite young, and new to this, please answer as simply as possible.

Answer 1

Yes, in fact this concept was the basis of a number of science fiction stories including that described at https://en.wikipedia.org/wiki/Light_of_Other_Days

In a sense, the information carried by light to our eyes is always about an event happening in the past. It's just that since light travels so fast, the event would have to occured a very far distance away for the delay to be notable. Some of the stars we can see in the night sky may actually be of stars which have burned out or gone nova in the thousands or even millions of years it took for light to travel the distance.

If you could obtain some substance that significantly slows down the speed of light as it passes thru it (such as the 'slow glass' in the story referred to above), by holding a piece of it over one eye and looking at some event, you'd see the event in real time thru the other eye while the covered eye wouldn't see it until some time later.