Looking Back Through Time

[Sfoster15]

Looking back through time

 

So we all know that some the stars we can see on earth, as we see them, are as they were hundreds of millions of years ago due to the fact that light only travels so fast. So, hypothetically, if someone were to make a mirror and Send it out into space a hundred light years from earth. In two hundred years, would someone be able to see through that mirror and look at the earth as it is right now? could they see individual people and watch them?

[Staysys]

If you want to see the entire Earth then it would have to be a mirror at least as big as Earth itself.

 

It's one big misunderstanding about mirrors that if you get farther away you will have a wider field of vision, but that's not true. You will see the same amount of stuff inside the mirror no matter how far away it is, so if you are just using a handmirror you'll only be able to see your own face (if it's perfectly perpendicular to your vision).

 

But assuming you could make a mirror larger than the diameter of the Earth and you could launch it out into space so that after it is 100 lightyears from Earth its orientation will be perfectly pointing back at Earth, then 100 years after THAT event you will be able to see an image of Earth in the past.

NOTE: It won't be 200 years because the mirror probably took longer than 100 years to get 100 lightyears away. But you could do calculations to make it so that you could see 200 years into the past if that is what you want.

 

The problem is the Earth will be moving in a complex orbit relative to the mirror, so the mirror won't always be facing the Earth, maybe if it was rotating about all its axis you would be able to get images every period of its rotation.

Edited May 16, 2013 by Staysys

[Sfoster15]

Thanks

[swansont]

Short answer: from a timing aspect, yes. From an optical aspect, no way you can resolve that well at that distance.

[michel123456]

If you want to see the entire Earth then it would have to be a mirror at least as big as Earth itself.

 

It's one big misunderstanding about mirrors that if you get farther away you will have a wider field of vision, but that's not true. You will see the same amount of stuff inside the mirror no matter how far away it is, so if you are just using a handmirror you'll only be able to see your own face (if it's perfectly perpendicular to your vision).

 

But assuming you could make a mirror larger than the diameter of the Earth and you could launch it out into space so that after it is 100 lightyears from Earth its orientation will be perfectly pointing back at Earth, then 100 years after THAT event you will be able to see an image of Earth in the past.

NOTE: It won't be 200 years because the mirror probably took longer than 100 years to get 100 lightyears away. But you could do calculations to make it so that you could see 200 years into the past if that is what you want.

 

The problem is the Earth will be moving in a complex orbit relative to the mirror, so the mirror won't always be facing the Earth, maybe if it was rotating about all its axis you would be able to get images every period of its rotation.

(emphasis mine)

the bold part is not correct.

 

You can look at yourself entirely, from head to feet, in a mirror half your width and about 3/4 your height.(25 cm width, 140 cm height)

 

Make this little experience: stand in front of a mirror at about 60 cm of distance and mark upon the mirror the height and width of your reflected face (using a permanent marker).

My face on the mirror enters a rectangle 7cm width over 12 cm height, about half the real dimensions, at 60 cm distance.

 

The rest of the post looks correct to me.

[swansont]

(emphasis mine)

the bold part is not correct.

 

You can look at yourself entirely, from head to feet, in a mirror half your width and about 3/4 your height.(25 cm width, 140 cm height)

 

You can look at yourself entirely, from head to feet, in a mirror half your width and half your height, if it is placed properly.

[Staysys]

(emphasis mine)

the bold part is not correct.

 

You can look at yourself entirely, from head to feet, in a mirror half your width and about 3/4 your height.(25 cm width, 140 cm height)

 

Make this little experience: stand in front of a mirror at about 60 cm of distance and mark upon the mirror the height and width of your reflected face (using a permanent marker).

My face on the mirror enters a rectangle 7cm width over 12 cm height, about half the real dimensions, at 60 cm distance.

 

The rest of the post looks correct to me.

 

Ahh, yes you are correct sorry about that.

 

So it should be changed to say that the mirror would have to be at least as big as the radius of the Earth.

[Sfoster15]

But essentially it is possible with all the right equipment yes?