# Time travel?



## Varangian (Sep 13, 2011)

Einstein once said that time travel was possible via the speed one would have to travel. Anyone think this is possible?

For example:

1 km at 60km/h would take 1 min.

1 km at 120 km/h = 30 secs.

1 km at 240 km/h = 15 secs

1 km at 480 km/h = 7.5 secs

1 km at 960 km/h = 3.75 secs

1 km at 1920 km/h = 1.87 secs

1 km at 3840 km/h = 0.93 secs

1 km at 300, 000 km per second = ?? perhaps in the negative?


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## RJM Corbet (Sep 13, 2011)

Time contacts the faster you go, so you are going forward in time, relative to someone stationary. Less time passes for you than for the person who's not moving, so if 5 years passes for you, perhaps 10 years will pass for the stationary person.

But you also become heavier the faster you go, so the more power you need to accelerate. Eventually the electrons in the atoms of your body would be compressed into the atomic nucleii to become neutrons and your whole weight would be compressed into an area much smaller than the head of a pin. You would be a mini neutron star. 

If you could somehow reach the speed of light you would become infinitely heavy, but it would not be possible because you would need infinite force to reach the speed of light. That's called a singularity, where time and space and matter and force become infinite, so you would become a sort of black hole.

Everything breaks down at a singularity.

So you're asking what may come out of the other side? Is it negative? No. But something does. It's called Hawkins radiation, I'm not too sure what it is exactly though ...


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## Harpo (Sep 13, 2011)

Ah, this 'old' chestnut again - I'm waiting for the first working time machine to be invented, and for the first visitor-from-the-future to instantly step out of it when's switched on.


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## Vertigo (Sep 13, 2011)

Also you can only travel forwards in time by travelling at high velocities. You can't travel back. It's not really travelling in time anyway just a different frame of reference.


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## TheTomG (Sep 14, 2011)

I am always amused by the argument that a time machine is a self-inventing device. As soon as it is invented, the first thing you would do is go back in time and tell yourself how to invent it, thus accelerating the date of its invention.

Then anyone who used it would do the same, so that they could profit or benefit from it, and in this way the invention of the time machine would always move backward in time - thus, if time travel was possible, we'd already have invented it.

Fun thoughts!


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## Huttman (Sep 14, 2011)

There is a way to travel back in time...enter into an earlier time zone.
Other than that it is not possible to go backwards in time. What would be some reasons for traveling back?


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## Varangian (Sep 14, 2011)

I'd go back to 1066 AD and make damn sure the Vikings won the Battle of Stamford Bridge! That done I'd take a Berserker and bring him forward in time and strategically place him right beside Hitler in a sound proof room.


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## Quokka (Sep 14, 2011)

Yep forward time travel (or at least time not being a constant) is a proven fact. Everytime someone goes up in a plane they experience a tiny fraction of a second difference in time passing compared to those on the ground. 

http://en.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment 

Lots of other experiments done as well of course, I was trying to discuss it with a mate once who thought anything like that was pure science fiction, then I made the mistake of mentioning how weak gravity was meant to be, he replied that "gravity was the strongest force there is, holds the universe together" and we went of on another tangient all together .

I remember reading an article in New Scientist once about a time travellers convention and the organisers stated that although no time travellers attended the convention then, they were still hopefull that someone would attend the day at some point.


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## J Riff (Sep 14, 2011)

There's no physical way, and probably won't ever be, but there are two ways to witness the past.
 A virtual telepathic recording of a past event allows you to be there and experience it, sights, sounds, smells, everything.
 Or, one could somehow catch up with reflected light, say from the Earth of ten thousand years ago, and have a look at that.


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## RJM Corbet (Sep 14, 2011)

Excellent observations, _Riff_ ...


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## TheEndIsNigh (Sep 14, 2011)

J Riff said:


> There's no physical way, and probably won't ever be, but there are two ways to witness the past.
> A virtual telepathic recording of a past event allows you to be there and experience it, sights, sounds, smells, everything.
> Or, one could somehow catch up with reflected light, say from the Earth of ten thousand years ago, and have a look at that.


 

Er...

So time travel isn't possible but FTL - a piece of cake?


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## RJM Corbet (Sep 14, 2011)

TheEndIsNigh said:


> Er...
> 
> So time travel isn't possible but FTL - a piece of cake?



I think Riff's saying that if you could get far enough away from the earth, you could look back into the past, as we do with distant stars, so if you travel at say 2/3 light speed for 20 years, you would be able to look back and see your friend Mike as if he had only aged by 20 years, when in fact, by his own time he's aged by 60.

But you're right _TEIN_, you couldn't get ahead of the light beam, no matter what you do so ...


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## Vertigo (Sep 14, 2011)

Quokka said:


> Lots of other experiments done as well of course, I was trying to discuss it with a mate once who thought anything like that was pure science fiction, then I made the mistake of mentioning how weak gravity was meant to be, he replied that "gravity was the strongest force there is, holds the universe together" and we went of on another tangient all together .


I always say to anyone who says something like that, that if it was the case then you would be able to stand up, never mind jump in the air. *We* are stronger than gravity!



RJM Corbet said:


> I think Riff's saying that if you could get far enough away from the earth, you could look back into the past, as we do with distant stars, so if you travel at say 2/3 light speed for 20 years, you would be able to look back and see your friend Mike as if he had only aged by 20 years, when in fact, by his own time he's aged by 60.
> 
> But you're right _TEIN_, you couldn't get ahead of the light beam, no matter what you do so ...


 
I think Riff was saying something more on the lines of putting up a great big mirror say 50 light years out and then look at the reflected light. Once set up you would have a 100 year window into the past. Obviously you couldn't retrospectively look back into time before the setting up of the mirror.

Actually if it was possible to set up a perfect reflector (and I do mean perfect) you could just set light bouncing back and forth between two of these reflectors perfectly parallel to each other and then tap into it whenever you liked. Theoretically possible, practically I don't somehow think so.


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## Quokka (Sep 14, 2011)

So we could watch Jurassic Big Brother as long as someone else hits the record button, which we can't ask them to do..... unless information can travel FTL.


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## Vertigo (Sep 14, 2011)

Precisely - you would have to decide that this would be interesting to people in the future and set it "recording" *then* afterwards it's too late. Which really makes it no better than recording the event to some media and then storing it which after all is a form of window into the past.


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## Harpo (Sep 16, 2011)

TheTomG said:


> I am always amused by the argument that a time machine is a self-inventing device. As soon as it is invented, the first thing you would do is go back in time and tell yourself how to invent it, thus accelerating the date of its invention.
> 
> Then anyone who used it would do the same, so that they could profit or benefit from it, and in this way the invention of the time machine would always move backward in time - thus, if time travel was possible, we'd already have invented it.
> 
> Fun thoughts!


 
Nope, if a time machine is a machine _in which a traveller travels, _then that traveller may travel to and from any time within the active existence of that machine (think in terms of the teleport machines in "The Fly" film, they stay where they are and Jeff Goldblum teleports from one to the other).  Hence a time machine does not itself travel at all, it merely exists for a duration of time.  (think also of roads, they go everywhere but they stay where they are, drivers can travel along the length of a road in either direction)


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## TheTomG (Sep 16, 2011)

That's a new twist on it for me, cool - time portals or time transporters, rather than the HG Wells style concept of an actual vehicle able to travel with its occupant to times in which neither existed.

Whichever form you go with be sure to observe the rules of Chekov's gun - if you introduce a gun in the third act, be sure it is fired in the first act.


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## Metryq (Sep 16, 2011)

Harpo said:


> Nope, if a time machine is a machine _in which a traveller travels, _then that traveller may travel to and from any time within the active existence of that machine



Some time machines work that way, but not all of them. H.G. Wells' _Time Machine_ was like a car, rather than your "roads of time." The "ghost of Christmas past" in Dickens' _A Christmas Carol_ is also "car-like" and not "road-like."

Granted, there are road-like time machines, such as Asimov's Eternity in _The End of Eternity_, the Guardian in the popular _Star Trek_ episode "The City On The Edge of Forever," and H.G. Wells' machine in Karl Alexander's novel _Time After Time_.

Then there are those "artillery-style" time machines that project subjects into the past or future without benefit of a receiving station, like Pipe Organ in James P. Hogan's _The Proteus Operation_ and the Skynet time machine in _The Terminator_ movies.


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## J Riff (Sep 17, 2011)

Maybe just amplifying the light enough... it reflects off the Earth, hits a distant shiny planet and reflects back and forth like a pinball. All we have to do is see it and start a TV channel. The Real History Channel.)


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