Can you see the back of your head

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In summary, the conversation discusses the possibility of seeing the back of one's head with a powerful telescope while standing on a mountain. It is determined that this is not possible due to the curvature of light around the Earth and the concept of a photon sphere near a black hole. It is also mentioned that the shape of the universe may not be round.
  • #1
jamesabc
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if you stood on a mountain would you be able to look straight ahead with a powerful telescope and see the back of your head? or would you just look out into space?
 
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  • #2
I just use a mirror.
 
  • #3
You would just look out into space - light doesn't curve around the Earth like that.
 
  • #4
Division said:
I just use a mirror.

Or two?
 
  • #5
Depends on where the mountain is. Assuming your eyes lie on the events horizon you should be able to see your back.
 
  • #6
Borek said:
Depends on where the mountain is. Assuming your eyes lie on the events horizon you should be able to see your back.

Quite so... except that you don't need to be quite that close.

Orbits around a black hole are ... different. The "photon sphere" is the distance from a point mass at which light moving tangentially will follow a perfect circle around the mass. For a non-rotating black hole, this is 1.5 times the Schwartzchild radius (event horizon).

Cheers -- sylas
 
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  • #7
Borek said:
Depends on where the mountain is. Assuming your eyes lie on the events horizon you should be able to see your back.

This doesn't work, as the light will just fall into the black hole. You have to be at the photon sphere, which is a bit farther from the black hole. See

https://www.physicsforums.com/showthread.php?t=246751.

Maybe the original poster is thinking about closed universes.

[edit]Didn't notice that sylas posted while I was searching.[/edit]
 
  • #9
Photon sphere... one learns all his life and dies stupid :wink:
 
  • #10
Borek said:
Photon sphere... one learns all his life and dies stupid :wink:

Especially if you see your back :smile:
 

FAQ: Can you see the back of your head

Can you physically see the back of your head?

No, it is physically impossible for a person to see the back of their own head without the use of mirrors or other devices.

Why can't humans see the back of their own head?

Humans have a limited field of vision and our eyes are positioned in the front of our heads, making it impossible for us to see behind ourselves without aid.

Can some people see the back of their head?

No, regardless of any special abilities or conditions, it is not possible for any human to see the back of their own head.

Is there any way to see the back of your head without using mirrors?

Technically, no. However, some people have been able to use certain techniques, such as projecting mental images or using out-of-body experiences, to see an image of the back of their head.

Can animals see the back of their heads?

Most animals have a wider field of vision than humans and their eyes are positioned differently on their heads, allowing them to see more behind themselves. However, they still cannot see the direct back of their head without using mirrors or other devices.

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