So, I had an amazing idea in the shower this morning. It's something that I don't expect to come about in my lifetime in reality, but I don't know why sci-fi writers haven't thought of it. (Okay, maybe some have, but not anything I remember reading, hearing, watching, etc.)

The gist of it is this: You know how space is big? The distance between us and anything outside of the solar system is measured in light years. A light year, of course, being the distance that light travels in one year. I imagine most people are at least passingly familiar with this idea. The fact that it would take us a massively long time to get to any other stars, even if we were able to travel at the speed of light. What I don't think most people really GET, though, is that this means the light we are seeing from these stars (and other objects) takes a long time to get to us. So, if a star we're looking at is 100 light-years away, we're seeing light that left the star 100 years ago. So we're basically seeing back in time. We're seeing the star as it was 100 years ago.

So, my amazing idea was that, if we can ever develop faster-than-light travel (FTL), it would be an absolute windfall for historical research, including natural history. For example, if you wanted to see something that happened on Earth 100 years ago, you could just jump in your FTL starship and travel 100 light-years away, then stop and look back at the Earth. You would then be seeing light that left Earth 100 years ago. And, assuming we have telescopes with good enough resolution to see enough detail at 100 light-years, you could see what was happening on Earth at that time.

Again, assuming you have good enough telescopes by then, you could look back a thousand years, a million years, a billion years, etc., if you just go far enough away.

Now, to really get a good picture of what's going on, you'd need to send out multiple ships in different directions (my guess would be, four ships, in a "d4" pattern -- i.e., one "straight up", and the other three angled down in a "triangle" -- this would probably let them each see enough of the planet that they could pool their data when they got back and put together a complete picture of the planet at that time. Considering that the Earth would still be rotating, so each ship's view of the planet would change as it rotates.

Doing this, and going out the right distance, could allow you to conclusively prove what happened at certain points in history. (Again, assuming, of course, you have telescopes with good enough resolution to see it clearly at that distance. And assuming it happened outside, so it can be seen from there. 8^)

Heck, it could conclusively prove how the planet, and solar system, formed in the first place!