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They do it with mirrors (Posted on 2006-04-26) Difficulty: 3 of 5
If I stand in front of a mirror, the light takes a finite, albeit small, amount of time to reach my eye.

So I am seeing myself as I looked some small fraction of time in the past.

Now if I stand with a second mirror behind me, I can see an infinite number of images of myself, each slightly older.

If I had my arm raised, and then I lowered it, can I still see an image of myself with raised arm?

No Solution Yet Submitted by goFish    
Rating: 3.7500 (4 votes)

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Solution re: Not without help | Comment 2 of 8 |
(In reply to Not without help by Rollercoaster)

Not ony that, but with mirrors 10 feet apart, there would be about 10million reflections.

No mirror is perfectly reflective.  Even with mirrors that reflect 99.9999% of the incoming light less than one ten-thousandth of the light would make it all the way to your eye.

Any deviations of the mirrors from being perfectly flat would also also be magnified 10,000,000 fold. 

Then there's the angle between the mirrors.  If they deviate from being parallel by 1/100,000 of a degree your image would be off by 200 degrees - anything over 180 is beyond what any size mirror could show.

So as posed, I think it's physically impossible.

One way it could be accomplished (pardon the cliche):  Take a picture, it'll last longer.

  Posted by Jer on 2006-04-26 13:19:19
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