I don’t believe in backwards time travel, but
would it be theoretically possible to see back into time?
Take the ‘dots on a balloon’ model of the universe. A two dimensional being from that model would be able to look, given the proper optics, etc, all the way ‘around’ the balloon and see what had happened in the years past by collecting light rays from that time period. If we live in a closed universe, would that same effect be theoretically possible?
Hope that made sense.
A friend of mine who I consider to be impeccably honest told me that he used to astral travel quite a lot. He would travel all around the city and even made a trip far into the stars before he realized how lonely he would be out there if his body died before he got back.
He never mentioned going back in time, although I would imagine an astral body would fit the definition of a two-dimensional being in your theory.
I’ll ask him next time I see him.
I don’t recall for sure what exactly the conditions are, but I believe that in a closed universe, you could only see the back of your head at the instant that the universe finished recollapsing to a point (the Big Crunch). I think, though, that this result might be for a special case of the cosmological parameters, and I’ll have to dig through my notes before I can be more sure. Hopefully someone smart like Chronos will be by to confirm or refute this!
Well, truth is we’re always looking back in time. That is, light from somewhere takes time to get to our eyes.
When you look at a star X lightyears away, you’re seeing what it looked like X years ago.
Unfortunately we can’t pick and choose what we get to look at when.
Oh, and Leroy, tell your pal to lay off the acid.
This response is I’m sure full of holes and very unscientific, but here’s my two cents anyway.
It seems to me that the only reason anyone ever really sees anything is because light bounces off of an object, hits the viewers eye, the brain then interprets that light and processes the image. Some of the light that bounces off that object must shoot off into space. If we had some vehicle that could travel faster than the speed of light we could theoretically chase the light that bounced off of say, Millard Fillmore jacking off in the White House bathroom, actually pass that light, turn around and using some device that could interpret that light and process the image like our brains do, we could see Millard Fillmore whacking away as if it were happening that moment right in front of you.
I look excitedly forward to the future.
Quantum mechanics implies that information can never be destroyed*, so I think it’s theoretically possible to reconstruct everything that ever happened.
[sub]*A drastic oversimplification, I know.[/sub]
Candlemas, if your idea of an exciting future is seeing our most popular president in the throes of self-fulfillment, I’m already worried about you after only two posts.
Candle, going faster than light=going back in time.
What can I say Dijon? The heart wants what the heart wants.
There have been quite a few science fiction stories about this. See E for Effort by Karras (?) in The Science Fiction Hall of Fame (Vol. I) for one example. I know that Asimov wrote one, too. After reading these you’ll be convinced that this probably isn’t a great idea.
I also don’t see how it can be done. One theory is that, as you go farther from the earth you can catch up with light rays that were emitted long ago, so you just arrange to travel faster than light (ha!), turn around, and look back. Of course, travelling faster than light is a real problem for some people, but assuming that you do, nothing absolves you of the laws of imaging physics. You still can’t see anything that’s smaller than the resolution limit of your apparatus. Lotsa luck seeing anything that’s of less than astronomical dimensions. (This scenario, by the way, shows up in The Invisible Ray, a 1930’s sf/horror film with Boris Karloff and maybe Bela Lugosi. My favorite part is looking back at the earth and watching it rotate – there aren’t any clouds.)
[tip-toes in, non-scientifically]
Given that it takes time for light to bounce off any object, enter through the eyes and be interpreted by the brain (albeit it fractions of a second), surely everything we see is ‘historical’, to some degree.
It’s not possible to see ‘the now’ until it becomes ‘the then’.
[/tip-toes out in the direction of a suitable couch]
Hmmmm… I recall Mr. Hofstadter writing something in Godel, Escher, Bach about collecting residual vibrations left over after hundreds of years to make a recording of Johann Sebastian himself playing the harpsichord.
Of course, that would be HEARING the past rather than SEEING it, but for plenty of people hearing is better that seeing.
– CH
Czechistory raises an interesting point. A few years back, Arthur C. Clark wrote a story where a scientist was able to make a sound recording from an ancient pot. the idea was that the potter’s fingers acted like a phonograph needle in the wet clay-making a sound recording of the noises in the potter’s shop-much like the first Edison phonograph. Does anybody know if this was ever actually tried?
The Asimov story was called “The Dead Past”. A classic story, with a quite unnerving ending. Damon Knight wrote a rather different take on the theme, “I See You”.
I do time travel constantly. I seem, however, to be stuck in my lowest forward gear along with the rest of you, except when you are explaining yourselves, it seems that I already know what you are going to say.
And yes, we can look back in time, that is what astronomers do. Unfortunately they are somewhat limited in the time window the view allows them.
I posted something along those lines in GD, and got spanked over chaos theory, which I was told would invalidate any notion of a clockwork universe by which conservation of information would work.
[quoteA few years back, Arthur C. Clark wrote a story where a scientist was able to make a sound recording from an ancient pot. the idea was that the potter’s fingers acted like a phonograph needle in the wet clay-making a sound recording of the noises in the potter’s shop-much like the first Edison phonograph. Does anybody know if this was ever actually tried?[/quote]
It asn’t a story – it was in an essay that was later collected in his book The View from Serendip. Clarke was reporting on an article in an IEEE journal by someone who had already tried it, and claimed success. I’v got a copy of the article, somewhere. He also noted that “Daedalus”, the tongue-in-cheek inventor who has a regular column in the journal Nature, had also suggested the idea one week. (Daedalus and Cecil should get together sometime – it would be an interesting session. There are people who’d probably pay real money for a photo of them, to prove that either one really existed).
I wrte a story based on the idea once, but I couldn’t persuade anybody to print it.
In any event, this idea is about re-creating sounds from ancient recording media – noisy potter’s wheels, brushes on paint, etc. It’s not about reconstituting sounds from “vibrations”, a notion that sounds pretty looney.
That was also the plot of an X-Files episode where a potter had unintentionally recorded the voice of Jesus raising Lazarus from the dead.
While information is probably preserved in an absolute sense, the cost of collection and interpretation increases very quickly to the point where it is not possible to retrieve the information. There should be two factors providing an absolute limit here: Available energy in the universe. And uncertainty principles. I think the second is generally going to bite first but it would depend on the level of detail that you required and the time/space period over which you are viewing.
I remember having an idea about using a black hole for something like this. If you were to shoot a beam of light just outside the event horizon, the black hole’s gravity would slingshot the light back around at you (or so it seems to me). If you want to see some photons that left Earth a hundred thousand years ago, you just need to look at a black hole 50,000 light years away.
Of course, you still have all the practical problems with resolution, etc., but I thought it was an interesting idea.