# Can I see the past in this way?

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According to physics theory, in this world, nothing can travel faster than light. However, if we do faster than light, will we see the light which is given off in another world? I mean: Can we see things happening in the past or in the future in this way?

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In theory, if you left the earth and had a magical telescope pointed at it, as you got past the speed of light (assuming that you could do so for the sake of argument), you would see events on earth rewind, as you'd be catching up with and overtaking the light that had already left. The faster you went, the greater the rewind speed.

When you wanted to view something in the past in normal time again, you'd simply slow down to below lightspeed just before the event you wanted to see.

It would be great....Tyrannosaurus Rex vs Triceratops etc

Shame it's not possible!!

Rob

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In theory, if you left the earth and had a magical telescope pointed at it, as you got past the speed of light (assuming that you could do so for the sake of argument), you would see events on earth rewind, as you'd be catching up with and overtaking the light that had already left. The faster you went, the greater the rewind speed.

When you wanted to view something in the past in normal time again, you'd simply slow down to below lightspeed just before the event you wanted to see.

It would be great....Tyrannosaurus Rex vs Triceratops etc

Shame it's not possible!!

Rob

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• 2 weeks later...

I was thinking the other way:

If we are able to put a mirror one light year away from Earth, the mirror supposed to reflect the light back to Earth.

So, what we do is just observe the mirror from the Earth. The to and fro for light to travel is 2 light years. Therefore, we can see what we did two years ago from the time we observe the mirror with a telescope. XD

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If we were to travels faster than light, we wouldn't be able to see the the light as we looked back, as it wouldn't be able to catch up. the best you could hope for is to travel at the speed of light and see everything in freeze frame. Besides, surely it would be so red shifted that you'd need to use a radio reciever to 'see' it.

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If we were to travels faster than light, we wouldn't be able to see the the light as we looked back, as it wouldn't be able to catch up. the best you could hope for is to travel at the speed of light and see everything in freeze frame. Besides, surely it would be so red shifted that you'd need to use a radio reciever to 'see' it.

would you need to look back?

you could just look forwards and let your eyes crash into the photons

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would you need to look back?

you could just look forwards and let your eyes crash into the photons

I wonder what backwards light would look like?

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If we were to travels faster than light, we wouldn't be able to see the the light as we looked back, as it wouldn't be able to catch up.

You'd be able to see the light that had left before you did, hence seeing into the past.

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There's something distinctly odd about discussing how the "normal" laws of physics would work once you've already made the assumption that they don't apply

James

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sorry...I've tried, but I cant resist this

I wonder what backwards light would look like?

thgil

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You'd be able to see the light that had left before you did, hence seeing into the past.

So, if we were travelling faster than it, it would be receding away from us (us looking back at our origin), only if we were looking towards the older light would we be able to 'see' it, giving us an image of, well, what? An reversed image of our origin? Do photons have a front and rear? Would the light hitting our eyes 'backwards' still look like light?

I now need to lie down for a while....

N.B. I am merely a roughneck done good, such things as physics are beyond by humble understandingses...

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You'd be able to see the light that had left before you did, hence seeing into the past.

Only if you stopped and looked back.

If you were still travelling faster than the speed of light and you looked backwards you would see...?

I'd guess nothing as no light would be travelling fast enough to enter your eye.

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:icon_scratch:Nonsense! But enjoyable nonsense nevertheless.

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Place a mirror 1 AU from the earth.. then observe the earth's reflection. 8 minutes there and 8 minutes back - 16 minutes into the past.

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^^^ that would have to be one HUGE chuffin' Mirror!

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IF we did break the light barrier, would there be an optic boom? Might we burst out of the universe? What would we burst into and how would we get back? Would we want to get back?

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and now, back to the index with a bafuddled look on ones face

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IF we did break the light barrier, would there be an optic boom? Might we burst out of the universe? What would we burst into and how would we get back? Would we want to get back?

Sonic boom is that the air sound waves can't get out of the way so logically you would have a situation where you'd catchup with the light in front.

It's very interesting - there's nothing to change the wave length of light. There overall energy would accumulate but at the same wave length. Perhaps a warp in space-time provides a mechanism to change wave length and allows the energy to tunnel away from the junction causing a leak like a black hole.

Otherwise the atoms at the front of the craft would then have to deal with the energy levels caused by absorbing the energy. Light friction.

Just pie in the sky ideas.. flibble..

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Isn't everything we observe in the past? In the sense that it takes light a certain amount of time to reach our eyes and it then takes a another amount of time for our brain to process the information.

Granted it's not a long time in the past, about 1/10th of a second iirc, but it's still in the past.

I must say I find it quite bizarre to think that everything I see around me happened about 1/10th of a second ago, and what I think of as now isn't now at all.

Perhaps I've got it all wrong though.

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Some Buddists say that there is no past nor is there future. There is only the present and that the present is just an illusion...

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Some Buddists say that there is no past nor is there future. There is only the present and that the present is just an illusion...

Yes, but don't they also believe that stones are alive? I seem to recall an Alan Watts lecture where he said it in all seriousness, in which case I don't think we should take anything they say too seriously.

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• 3 weeks later...

To quote on of my favourite sceptics and rationalists, Tim Minchin:

"Science adjusts it's beliefs based on what's observed.

Faith is the denial of observation so that Belief can be preserved."

Tim Minchin, "Storm"

If you haven't heard Storm, its well worth a listen.

Alan

Edited by inksmithy
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• 2 weeks later...
Only if you stopped and looked back.

If you were still travelling faster than the speed of light and you looked backwards you would see...?

I'd guess nothing as no light would be travelling fast enough to enter your eye.

I agree with that

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Place a mirror 1 AU from the earth.. then observe the earth's reflection. 8 minutes there and 8 minutes back - 16 minutes into the past.
You could imagine a black hole, of just the right mass, so that light made one loop and returned?
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Some Buddists say that there is no past nor is there future. There is only the present and that the present is just an illusion...

Maybe not only the Bhuddists. In philosophy of science, and indeed in hard physics, there is an awareness that past-present-future is a theory of time. It is so much a part of our thinking that we tend to forget this. But we should doubt it. I certainly doubt it, but I also accept that my little brain has not evolved to grasp an alternative view very easily. Or at all!!!

Olly

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