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Universal time-delay surveilance

Look into the past using a big mirror in space
  [vote for,

The basic system would consist of a big mirror in a distant orbit around the sun pointing towards earth. The orbit would be chosen so light travels from the earth to the mirror and back in a couple hours up to maybe a day or more. That distance will of course vary. When there is a crime, disaster, or other event on earth that is discovered shortly after it occurred, high powered telescopes could be used to watch the event in the reflection of the mirror several hours after the fact. Of course more than one mirror could be used to provide different time delays, different angles and fuller coverage of the earth.

- Our telescopes aren't powerful enough. This could be improved somewhat (but not fixed) by making the mirror somewhat curved. In the extreme, the mirror could be curved so that it focused on the earth, but then it only focuses on a single location on earth, and only works for a certain distance, so make it somewhat less curved.
- Constructing a mirror large enough and perfect enough is beyond current technology.
- It would probably be more cost effective to just have security cameras installed everywhere.

If this could work, Police investigators would request surveillance of a certain location over a certain time period in the past. Depending on the importance of the crime and the availability of telescopes, a low priority crime might be assigned a low quality telescope, resulting in a poor image. Major events (say an assassination terrorist attack or natural disaster might get all of the telescopes assigned to them to capture as much data as possible. For example, a lost airliner could be tracked from takeoff to crash by a single telescope, but because of its importance would probably be assigned multiple scopes to make sure it didn't get lost again.

scad mientist, Feb 25 2015

CSI zoom enhance http://youtu.be/3uoM5kfZIQ0
The zoom enhance scene I mentioned [xaviergisz, Feb 26 2015]


       OK, so if we want a 1hr delay, the mirror has to be 0.5 light-hours away, or 335 million miles away. That's mid-way between Mars and Jupiter.   

       Also, I'm pretty sure that you'd have to remove Earth's atmosphere for this to work. Not just because it's often cloudy, but because any variation in atmospheric refraction is going to completely screw things. Consider that stars twinkle, even though their light is being wiggled (by the atmosphere) only over a distance of a few 10s of kilometres. Now multiply that distortion by about 10 million-fold.
MaxwellBuchanan, Feb 25 2015

       Satellites can currently photograph the earth surface through the atmosphere. The telescopes looking into the mirror need to be space based. (definitely would need to be to look at the mirror during the day).   

       I guess the distortion would still be much worse for a telescope effectively much farther from the atmosphere, than a telescope looking at earth from just past outside the atmosphere...
scad mientist, Feb 25 2015

       There's no atmosphere beyond the atmosphere, [mb]
pocmloc, Feb 25 2015

       Yes, [poc], I am aware of that. That's not the point I was making.   

       Suppose that the atmospheric turbulence is enough to deflect light by 0.01 degrees. This means that a light ray, travelling through the atmosphere to the surface of the earth, will be shifted by quite a small amount (ie, an angle of 0.01 degrees, over a distance of say 30km).   

       Now imagine a light ray going out through the atmosphere, towards our mirror. It is still deflected by the same 0.01 degrees, but it now travels (on this deflected path) over a 300-million mile journey.   

       Hence, the distance by which it has been deflected, by the time it reaches the mirror, will be huge.
MaxwellBuchanan, Feb 25 2015

       So people would just do their crimes at night or under cloud cover or indoors as they already do. And planes would continue to crash at night or during inclement weather.   

       Using space as a recording medium is kind of clever. But I'm not sure how useful this would be.
the porpoise, Feb 25 2015

       Night: There's no reason this couldn't use infrared. Of course it can't see indoors or in some weather, but it would (if it was possible) help in many situations.
scad mientist, Feb 25 2015

       This is significantly less realistic than the magical CSI zoom and enhance. I vaguely remember one episode where there was security footage of a victim being killed, but the killer was out of frame. Not to worry, the clever CSI team simply zoomed and enhanced into the reflection of the victim's eye ball to reveal the identity of the killer.
xaviergisz, Feb 25 2015

       atmosphere: Place the mirrors of both ends outside atmosphere. Thus only the first and last lap travel through atmosphere. Remaining intermediate bouncings will occur only in clear space. This should keep distortions/absorption at minimum.
VJW, Feb 26 2015

       Hmm, looks like you may be right. Perhaps the atmosphere should be removed during crimes?
pocmloc, Feb 26 2015

       // less realistic than the magical CSI zoom and enhance // Well, other than the atmospheric distortion issue which may limit this to investigations of crimes in space, there's nothing other than current technological limits preventing us from creating a huge moon-sized telescope that can see that far and a reflector twice the size of Jupiter to go with it. On the other hand there is no technological advance that would enable extrapolating a detailed image from a small handful of pixels.   

       However since CSI does have that technology, the script writer ought to have someone snap a photo of the moon a short time after a crime occurred. CSI investigators could then use their zoom and enhance to catch the killer using the mirror off the lunar rover.
scad mientist, Feb 26 2015

       The CSI zoom and enhance is possible if you have a 100 gigapixel security camera. I suppose your idea could work too, it is just a few orders of magnitude more difficult.
xaviergisz, Feb 26 2015


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