Is this plausible? http://www.nanowrimo.org/en/forums/reference-desk/threads/49980 Xyex So, I've had a new idea for a new Sci-fi novel, but I need to know if one of the main underlying plot points is even plausible. I know the light we see from stars is thousands, millions, and even billions of years old, and my question is this: If we either found or created some sort of reflective surface out in space that was bouncing back the light from our system, and we had an advanced enough telescope and imaging software, would it be possible to observe the Earth of the past? Wed, 08 Feb 2012 02:11:59 +1000 http://www.nanowrimo.org/en/forums/reference-desk/threads/49980?page=1#forum_thread_comment_1122138 http://www.nanowrimo.org/en/forums/reference-desk/threads/49980?page=1#forum_thread_comment_1122138 cosmam It would absolutely be possible. The problem (which is a common problem with time machines), is that you wouldn't be able to see any earlier than when you launched the mirror, if the mirror is constrained to travel at the speed of light or less. If you get into wormholes or hyperspace, then the mirror could "outrun" the light leaving Earth and look into the past. The other problem is that, at any significant distance, it's *REALLY* hard to see planets. We mostly only "see" them by noticing their effects on nearby stars (and those are the big ones (think Jupiter size)). Seeing smaller planets is much more difficult, and even then details (continental scale or smaller) are basically impossible (with current technology). Wed, 08 Feb 2012 02:21:48 +1000 http://www.nanowrimo.org/en/forums/reference-desk/threads/49980?page=1#forum_thread_comment_1122147 http://www.nanowrimo.org/en/forums/reference-desk/threads/49980?page=1#forum_thread_comment_1122147 keolah There's really no need for a 'reflective surface' for that. What you'd need to make it work usefully would be two things: 1) Faster than light travel. 2) Extremely advanced magnification and imaging technology. With those two things, all you'd need to do is use #1 to go to a system, say, 500 lightyears away, and using #2, they'd be able to observe Earth 500 years in the past. Our current technology level is nowhere near the point of that sort of technology being possible, but I won't rule out the possibility in the future. After all, just a hundred years ago, the idea that we'd now have satellites capable of reading license plate numbers would be ludicrous. Just remember that it would be limited by the position of the Earth relative to the receiving end -- you'd need an analysis station on the other side if you wanted 24-hour coverage. And the weather might also interfere. Wed, 08 Feb 2012 04:57:21 +1000 http://www.nanowrimo.org/en/forums/reference-desk/threads/49980?page=1#forum_thread_comment_1122295 http://www.nanowrimo.org/en/forums/reference-desk/threads/49980?page=1#forum_thread_comment_1122295 Xyex Thanks for the replies. I'd thought it was possible but I've had instances where my logic has been flawed without my realizing it, so... XD Thu, 09 Feb 2012 03:11:11 +1000 http://www.nanowrimo.org/en/forums/reference-desk/threads/49980?page=1#forum_thread_comment_1124175 http://www.nanowrimo.org/en/forums/reference-desk/threads/49980?page=1#forum_thread_comment_1124175 Phoenix I think the problem with 2 is that you'd need a *huge* "receiver" to collect the (intermittent) lightwaves before you could even begin--imagine the angles of reflection from the (moving and irregular) Earth's surface and how even an hours' worth of "video" would be sprayed out into space. Thu, 09 Feb 2012 07:15:17 +1000 http://www.nanowrimo.org/en/forums/reference-desk/threads/49980?page=1#forum_thread_comment_1124529 http://www.nanowrimo.org/en/forums/reference-desk/threads/49980?page=1#forum_thread_comment_1124529 lasalle202 If I understand what you are asking. 10,000 years ago, light from earth's sun heads off at light speed into the universe. It travels for 5000 years and hits large reflective object that bounces it back towards earth. Today the light has travelled for another 5000 years and is back at earth. Yes, we could tell what sunlight from Sol was like 10000 years ago, but that is about it. Depending upon the purity of the reflective surface, we might be able to tell that there were large planets like Jupiter and Saturn circling Sol, and we are getting to the point where we might even be able to detect earth. But could we actually see any prehistoric things crawling around on the surface of the earth? Nope. Thu, 09 Feb 2012 07:59:00 +1000 http://www.nanowrimo.org/en/forums/reference-desk/threads/49980?page=1#forum_thread_comment_1124622 http://www.nanowrimo.org/en/forums/reference-desk/threads/49980?page=1#forum_thread_comment_1124622 Notkieran There are limits to the resolving power of a telescope, and what you are talking about is beyond the resolving power of any telescope we have ever built, and possibly any telescope we might ever be able to build. Thu, 09 Feb 2012 12:47:10 +1000 http://www.nanowrimo.org/en/forums/reference-desk/threads/49980?page=1#forum_thread_comment_1125263 http://www.nanowrimo.org/en/forums/reference-desk/threads/49980?page=1#forum_thread_comment_1125263 keolah My advice, however, is don't let reality get in the way of a good story. Thu, 09 Feb 2012 15:41:54 +1000 http://www.nanowrimo.org/en/forums/reference-desk/threads/49980?page=1#forum_thread_comment_1125669 http://www.nanowrimo.org/en/forums/reference-desk/threads/49980?page=1#forum_thread_comment_1125669