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Looking Back in Time
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Hi All,
Please bear with me, I think I'm about to ask a set of really stupid questions here but I am genuinely interested in this and am not sure if a friend is pulling my leg or if he is just talking out of the proverbial.
We were talking about time travel last night (as you do) and he told me that if you were able to get to the furthest star (possibly planet but I think he said star) from the earth and had a powerful enough telescope you would be able to see dinosaurs on the earth. The reason for this apparently is to do with how long it would take for light to reach the star you're on, hence you would see past images as opposed to current one. My first question... is this even remotely true?
Also, if it is true, would it ever be possible to actually do this? Is this a way that we could actually travel back in time so to speak?
(If I've had my leg completely pulled, please try not to laugh me out of the science thread completely!)
Cheers China xx
Please bear with me, I think I'm about to ask a set of really stupid questions here but I am genuinely interested in this and am not sure if a friend is pulling my leg or if he is just talking out of the proverbial.
We were talking about time travel last night (as you do) and he told me that if you were able to get to the furthest star (possibly planet but I think he said star) from the earth and had a powerful enough telescope you would be able to see dinosaurs on the earth. The reason for this apparently is to do with how long it would take for light to reach the star you're on, hence you would see past images as opposed to current one. My first question... is this even remotely true?
Also, if it is true, would it ever be possible to actually do this? Is this a way that we could actually travel back in time so to speak?
(If I've had my leg completely pulled, please try not to laugh me out of the science thread completely!)
Cheers China xx
Answers
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No this is completely true.
Light travels at 186,000 miles a second so when you look at the sun 93 million years ago the light that is meeting your eye left 8 minutes ago.
The light from even the nearest star left over 4 years ago.
However in order to see back in time in this way you would have to travel faster than light to overtake the light conveying the picture. Travelling faster than light is generally accepted to be impossible.
Light travels at 186,000 miles a second so when you look at the sun 93 million years ago the light that is meeting your eye left 8 minutes ago.
The light from even the nearest star left over 4 years ago.
However in order to see back in time in this way you would have to travel faster than light to overtake the light conveying the picture. Travelling faster than light is generally accepted to be impossible.
I think jake meant the sun is 93 million miles away. Thus, in looking at it (with suitable protection of course), you are seeing the sun as it was 8 minutes before.
In the situation your friend describes, if you substitute "some kind of life form with a powerful enough telescope", then yes, it is possible that the light emitted from the Earth at the time of the dinosaurs (or any other time), would only now be reaching them, assuming they are sufficeintly distant from Earth.
To see the 'end of the Dinosaurs', their planet would have to be around 65 million Light years away from Earth (A Light Year is a measure of distance, meaning the distance light travels in one year).
This is basically true, though a "powerful telescope" capable of magnifying the minute amount of light would actually reach said distant planet, is stretching the boundary of reality somewhat.
As soon as you try to say "if you could get to the furthest star..." etc - (ie a human to be able to see these events) then the answer is no, for the reasons jake explained above.
In the situation your friend describes, if you substitute "some kind of life form with a powerful enough telescope", then yes, it is possible that the light emitted from the Earth at the time of the dinosaurs (or any other time), would only now be reaching them, assuming they are sufficeintly distant from Earth.
To see the 'end of the Dinosaurs', their planet would have to be around 65 million Light years away from Earth (A Light Year is a measure of distance, meaning the distance light travels in one year).
This is basically true, though a "powerful telescope" capable of magnifying the minute amount of light would actually reach said distant planet, is stretching the boundary of reality somewhat.
As soon as you try to say "if you could get to the furthest star..." etc - (ie a human to be able to see these events) then the answer is no, for the reasons jake explained above.
No, you can't change what you see by travelling anywhere, since you can't travel faster than the speed of light, then it makes no difference.
The light reaching us from a star that is 1000 Light Years away, will be the light emitted 1000 years ago. That is before you existed. - But since it is not the Earth, it doesn't have much context or relevance.
The only relevant context for 'looking back in time' would be looking at the Earth. To see this a hundred years ago, you would need to travel 100 light years away. Since you can't travel faster than light, this would take a hundred years at the speed of light. So when you looked back, you would only manage to see the Earth as it was at the time you left.
The light reaching us from a star that is 1000 Light Years away, will be the light emitted 1000 years ago. That is before you existed. - But since it is not the Earth, it doesn't have much context or relevance.
The only relevant context for 'looking back in time' would be looking at the Earth. To see this a hundred years ago, you would need to travel 100 light years away. Since you can't travel faster than light, this would take a hundred years at the speed of light. So when you looked back, you would only manage to see the Earth as it was at the time you left.
You're in rare form brachiopod, my fine, lophophore equipped friend! But, I would have an alternate view, in line with your last post. If, (I know, I know) one could travel at the speed of light (plus ten minutes to set up your telescope) no matter how far one travelled, on looking back, the best one could do is see themselves depart the Earth. Light travelling 93 millions of miles or 100 miles doesn''t really matter, one could only see (theoretically) the light that was emitted at the instant of lift off, so to speak. Now... if one could travel at twice the speed of light....
Out of interest (well I think its interesting) the most distant object ever seen from earth is a Galaxy 13 billion light years from earth. The view we see is from light that started out over 8 billion years before the formation of Earth.
http://www.msnbc.msn.com/id/4274187/
http://www.msnbc.msn.com/id/4274187/
There is a mirror on the Moon that reflects light back in the same direction from which it comes. With this mirror you can see laser light that was emitted from a laser on Earth about 2.57 seconds prior to its observation thereby allowing us to determine the precise distance of the Moon.
By turning a proverbial telescope to view a proverbial pre-existing mirror that reflected light from where the Earth was at that time we could, proverbially, observe the Earth�s distant past.
By turning a proverbial telescope to view a proverbial pre-existing mirror that reflected light from where the Earth was at that time we could, proverbially, observe the Earth�s distant past.
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