Possible to look into the past?

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poochyena
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Possible to look into the past?

Postby poochyena » Fri Jan 18, 2013 12:21 am UTC

So, i watch the science channel alot, and what i've gathered, its possible to look into the past, in theory, here we go

if somehow we were able to travel faster than light and/or be able to teleport to any location in the universe instantly, and we had with us a very very high powered telescope, and we teleported to a planet 500(or even 500million) light years away, would we be able to point that telescope to earth and see what it looked like 500(or 500million) years ago and be able to observe the activity on earth?

i say this because, when we look at stars, we are seeing what they looked like in the past, right? do we see the star in the past the same with the naked eye vs a telescope?

just wondering if its possible assuming we would be able to go faster than the speed of light and there are no planets in then way when looking at earth.

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Re: Possible to look into the past?

Postby yurell » Fri Jan 18, 2013 1:26 am UTC

poochyena wrote:if somehow we were able to travel faster than light and/or be able to teleport to any location in the universe instantly, and we had with us a very very high powered telescope, and we teleported to a planet 500(or even 500million) light years away, would we be able to point that telescope to earth and see what it looked like 500(or 500million) years ago and be able to observe the activity on earth?


Probably not. The problem is that at those distances, the light is so dispersed that spotting a planet would be notable (with our technology, anyway) — the idea of seeing anything happening on the planet is staggering. Your whole 'see into the past' aspect is correct, but the practical issues would, I think, prevent any use of it.

poochyena wrote:i say this because, when we look at stars, we are seeing what they looked like in the past, right? do we see the star in the past the same with the naked eye vs a telescope?


We look at the same light with our eyes as we do with our telescopes, so we see the stars in the same way, but telescopes have the advantage of being able to collect more light, allowing them to 'see' dimmer objects.

I hope that answers your questions!
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Re: Possible to look into the past?

Postby dudiobugtron » Fri Jan 18, 2013 1:27 am UTC

The basic answer to your question, ignoring FTL travel, is yes. A telescope isn't magic, it gets the same light that we would otherwise get with our naked eyes. All the light we see from stars came from that star a long time ago. If you were one light-minute away from Earth, all of the things you saw happening on Earth would have actually happened at least a minute ago. For someone 500 light years away from Earth, anything they saw happening on Earth would be 500 years out of date.
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poochyena
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Re: Possible to look into the past?

Postby poochyena » Fri Jan 18, 2013 2:37 am UTC

exactly what i was looking for, thank you very much! :D

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Re: Possible to look into the past?

Postby selfassembled » Fri Jan 18, 2013 3:22 am UTC

But something about my working interpretation of travel speed and time tells me that an FTL ship could also just go in circles around the earth and still end up in the past. Tachyons are thought to travel back in time and thus violate causality. The simplest way to imagine it is that as particles approach the speed of light they experience less and less time, photons do not experience time, so to speak; they do not decay naturally. To a photon the extent of the universe is an instant. Once crossing over that speed, time would begin to reverse.

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Re: Possible to look into the past?

Postby ConMan » Fri Jan 18, 2013 3:42 am UTC

More practically (so to speak), if you stuck a mirror on a spacecraft and shot it out 1 LY away, then somehow managed to align it perfectly, then you'd be able to see in its reflection an image of Earth from 2 years ago. We actually do this, in a fashion, with a laser pointed at a mirror on the moon, for which we can calculate the delay on with reasonable accuracy.
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Re: Possible to look into the past?

Postby doogly » Fri Jan 18, 2013 4:01 am UTC

But if you could travel faster than light in order to make this work, you could use that same exact mechanism to just travel back in time.
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Re: Possible to look into the past?

Postby idobox » Sat Jan 19, 2013 11:05 pm UTC

It is also possible to catch up with light if you travel in a straight line, and it doesn't.
For example, a massive black hole could bend the light , and allow you to travel faster than it.
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Re: Possible to look into the past?

Postby gmalivuk » Sun Jan 20, 2013 10:13 pm UTC

At that point, you could also just stay in one place and look at the light that's curved back to you.
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Re: Possible to look into the past?

Postby idobox » Mon Jan 21, 2013 9:30 am UTC

I suspect U-Turns require quite extreme conditions, and must therefore be quite rare. Also, by travelling, you can choose how far in the past you're looking.
But yes, staying on Earth and looking at extremely massive object with absurdly large telescopes is a possibility.
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Re: Possible to look into the past?

Postby gmalivuk » Mon Jan 21, 2013 7:58 pm UTC

Yes, extreme conditions like a black hole, which you'd already posited in your previous post.
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Re: Possible to look into the past?

Postby doogly » Tue Jan 22, 2013 5:00 am UTC

idobox wrote:I suspect U-Turns require quite extreme conditions

Mirrors are also things.
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Re: Possible to look into the past?

Postby shvedsky » Tue Jan 22, 2013 7:29 am UTC

poochyena wrote:So, i watch the science channel alot, and what i've gathered, its possible to look into the past, in theory,


You can achieve the same effect by watching camera recordings, in terms of the ability to do something with the information about the past you receive. Besides, cameras are not just a theory.

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Re: Possible to look into the past?

Postby dudiobugtron » Tue Jan 22, 2013 8:29 am UTC

Mirrors are a bit different - as I understand it they would absorb the light from Earth, and send out new light as a result. If using mirrors counts as seeing light from the past, then you should probably be allowed to use photographs as well.
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Re: Possible to look into the past?

Postby yurell » Tue Jan 22, 2013 8:42 am UTC

Ummm, you're not going to be looking at these photons directly anyway; a telescope employs mirrors, so how is that any different?
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