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Author Topic: Can you use mirrors to see into the past?  (Read 1862 times)

Offline thedoc

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Can you use mirrors to see into the past?
« on: 17/06/2014 05:30:01 »
Anon asked the Naked Scientists:
   
If I take 24 mirrors an placed them in a large room in front of one another in a straight line, then starting from the first moved each mirror until I could see it's reflection in the next. Until by the 24th mirror I can see all 23 mirrors in the final one.
Then stood in front of the first one an looked from one to 24 would I then see myself in the past ?
My maths are this
The eyes see at 30 FPS thus I equate that is equal to 00:03s on a timer ?
Thus if I divide
00:03 by 24 this equals = 00:72 of a second.

So therefore by the time you get to the 24th mirror your actually looking at yourself for 00:72 of a second in the past ?

Please please help !

I often listen to your podcasts and to your show on Radio 5 Live.

I've learnt so much so thank you.



What do you think?
« Last Edit: 17/06/2014 05:30:01 by _system »


 

Offline syhprum

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Re: Can you use mirrors to see into the past?
« Reply #1 on: 17/06/2014 09:44:33 »
To see an optical image delayed by 0.72 seconds you would need a light path of about 214,000 km, the best available telescopes would have a resolution of hundreds of meters per pixel at this distance so its not on apart from considerations of attenuation if mirrors are used.
 

Offline David Cooper

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Re: Can you use mirrors to see into the past?
« Reply #2 on: 17/06/2014 17:23:35 »
Easier just to use a video camera.
 

Offline evan_au

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Re: Can you use mirrors to see into the past?
« Reply #3 on: 17/06/2014 22:24:01 »
Quote
The eyes see at 30 FPS thus I equate that is equal to 00:03s on a timer ?
This is how quickly the human eye can respond to a changing visual signal, and is the basis for TV and film.
However, mirrors do not suffer from the limitations of the human visual system.
Mirrors will reflect photons at the speed of light (in common forms of glass, this is about 2/3 of the speed of light in a vacuum).

Quote
by the time you get to the 24th mirror your actually looking at yourself for 00:72 of a second in the past ?
I am afraid not.
If the room is (say) 3 meters wide, then the total distance will be 24x3m=72m; nearly all of this path is in air, so the speed of light is very close to the speed in a vacuum.
At the speed of light: 300,000,000 meters per second, this will introduce a delay of just 0.24 microseconds in total.

 

Offline jeffreyH

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Re: Can you use mirrors to see into the past?
« Reply #4 on: 18/06/2014 02:33:09 »
You don't need mirrors. Everything you see is already at some point in the past simply because light has had to travel from an object to your eye. The information is delayed. If light moved at 1m per second everything 1 metre away would be 1 second in the past. We never actually experiance the external world at the instant it is happening.
 

Offline yor_on

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Re: Can you use mirrors to see into the past?
« Reply #5 on: 20/06/2014 22:45:54 »
The question of the 'now', isn't it?

What is a 'now'?
 

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Re: Can you use mirrors to see into the past?
« Reply #5 on: 20/06/2014 22:45:54 »

 

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