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Author Topic: If you travel in time, but not in space, where would you end up?  (Read 9934 times)

Offline thedoc

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Michael asked the Naked Scientists:
My question is on a time machine which can travel in time but not space.

If you were at a point in the world and traveled trough time but not space, lets say backwards in time 3 years, would your location change due to the world turning and the fact that you cannot alter your location?
What do you think?
« Last Edit: 16/04/2008 16:40:14 by BenV »


 

lyner

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You'd need to get it right or you'd have a long walk home, holding your breath!
 

Offline syhprum

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Although actual physical time travel into the past is never likely to be possible (whatever that might mean) a very good simulation is possible by viewing old film etc.
No intervention is possible of course but that is considered not to be possible anyway, as movie cameras become more common and full immersion become possible we can almost say time travel into the recent past has arrived.
 

Offline turnipsock

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What if you were traveling way into the future and you stuck your elbow out of the window just to look cool, would your arm wither away to dust?
 

another_someone

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Michael asked the Naked Scientists:
My question is on a time machine which can travel in time but not space.

Space relative to what?  There is no absolute reference point in space, so there is no way of saying what 'not moving in space' actually means.
 

Offline Blueprint

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I wondered about this too.  If space-time is interweaved, and time is relative, how about travelling close to the speed of light on the spot (like a treadmill).  How would that affect the spacetime in which you are in?
 

another_someone

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I wondered about this too.  If space-time is interweaved, and time is relative, how about travelling close to the speed of light on the spot (like a treadmill).  How would that affect the spacetime in which you are in?

But again, relative to what are to travelling close to the speed of light?  To one observer, you may be travelling close to the speed of light, and yet to another observer, you may appear to be almost stationary.
 

Offline Blueprint

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I was wondering more of what would happen to that spacetime (say it was a spot on Earth), if someone was stationary and the other person was travelling close to the speed of light.  Would the speedy traveller just disappear? :)
 

Offline LeeE

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I wondered about this too.  If space-time is interweaved, and time is relative, how about travelling close to the speed of light on the spot (like a treadmill).  How would that affect the spacetime in which you are in?

Umm... I don't think it would affect the spacetime you are in at all, although you'd be exhausted from all the running.  The belt of the treadmill, on the other hand would experience time dilation and, as a consequnce, wouldn't suffer as much wear as you'd expect:)
 

Offline LeeE

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It seems to me that there are two ways of going back in time - either back the way you came, or by a different route.  If you go back the way you came you wouldn't be aware of it because everything, including your memory, would unwind together at the same time.  The alternative is to go via a different route, which means getting out of your current time dimension and either a) finding a way to jump back into it at an earlier point or b) finding a different time dimension travelling in the opposite direction so you can hop on and let it carry you back to your required stop.  Doing the instantaneous jump would be preferable as it wouldn't take any time whereas hopping on to a different time dimension would end up taking just as long to get back as it took getting there, assuming it went at the same speed.
 

Offline crypto

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I have thought about this before and it occurs to me that most films and books have got
this aspect of time travel wrong the only exception I can think of is Dr Who's TARDIS,
(Time And Relative Dimensions In Space) Which of course travels in time and space.

The Reason I think this, is mainly due to three quite obvious points when you think about them.

Reason 1: As you point out the earth is rotating so if someone were to travel in time
they would end up somewhere else on earth due to the rotation of the planet.

Let's say you are on the equator and travel one minute into the past
The earth is spinning at 1670 Kms (or 1038 Miles per hour)
So that mean you would be approximately 28 Kms (or 17 Miles) away from your starting position
Of course if you were to travel from the north or south pole you would pretty much remain where you are. 

Reason 2: Earth orbits the sun approx every 365.25 days So unless you were traveling in exact yearly jumps
when the earth occupies the same point around the sun each year (assuming that the orbit the earth take is not
changeable, which it is) you would end up in space.
 
Reason 3:(Big bang theory) Everything in the universe is traveling away from a central point.
So who is to say the Milky Way would have even been in the same spot 3 years ago?

I can just see it now, A scene from Back to the future.

Marty jumps into the Delorian to get away from the Libyan terrorists,
hits 88 miles per hour and is about to hit a retail booth when...

*pop*

He finds himself in outer space

"Oh man, this is heavy"

The Delorian then explodes due to the massive change in atmospheric pressure.

That sure would have been a short movie.

So that's my take on it anyway.

« Last Edit: 29/07/2008 04:54:09 by crypto »
 

Offline KALSTER

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(Big bang theory) Everything in the universe is traveling away from a central point.
This is a common misconception. There is no "centre of the universe".

It is not possible to travel in only time and not space, neither space and not time. Time is nothing more than a measure of relative movement. So if nothing moves (atoms, particles, strings, etc.), no time exists and visa versa.
 

Offline lightarrow

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Reason 3:(Big bang theory) Everything in the universe is traveling away from a central point.
So who is to say the Milky Way would have even been in the same spot 3 years ago?
The Milky Way has moved but not for the reason you write:
http://en.wikipedia.org/wiki/CMB
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From the CMB data it is seen that our local group of galaxies (the galactic cluster that includes the Solar System's Milky Way Galaxy) appears to be moving at 627 22 km/s relative to the reference frame of the CMB in the direction of galactic longitude l = 264.4o, b = 48.4o.
So, assuming (and not proved at all) that "travelled in time but not in space" means stationary with respect to that frame of reference, in 3 years the time traveller would find himself at something like 627*86,400*365*3 km away, that is 59 billions 319 millions 216,000 km away. Not exactly behind home...
 

lyner

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How about applying Newton 1 to the problem? If you don't actually provide a Force (impulse) just a 'time impulse', then you would carry on in the same direction at the same speed during your time journey. If you made it a brief 'time hop' you could end up not far from the rest of your original surroundings. It would only be the departure of your straight line trajectory from the curved path of the spinning, orbiting Earth which would cause your destination to be apparently shifted. You wouldn't need to chase  your launch spot - just make some corrections. Compared with the other, more basic, problems, this seems a trivial requirement.


Or, if the apparent or local time for which you were traveling was vanishingly short, the Earth wouldn't have moved any significant distance in any case.

Once you had built the engine, maybe you could finally find out, for certain, about our absolute motion through the ether!
 

Offline lightarrow

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How about applying Newton 1 to the problem? If you don't actually provide a Force (impulse) just a 'time impulse', then you would carry on in the same direction at the same speed during your time journey. If you made it a brief 'time hop' you could end up not far from the rest of your original surroundings. It would only be the departure of your straight line trajectory from the curved path of the spinning, orbiting Earth which would cause your destination to be apparently shifted. You wouldn't need to chase  your launch spot - just make some corrections. Compared with the other, more basic, problems, this seems a trivial requirement.


Or, if the apparent or local time for which you were traveling was vanishingly short, the Earth wouldn't have moved any significant distance in any case.

Once you had built the engine, maybe you could finally find out, for certain, about our absolute motion through the ether!
But this doesn't seem to match the initial question's requirement: "If you travel in time, but not in space, where would you end up?" If you don't travel in space means that your initial position, with respect to a sort of absolute frame of ref. (if it exists), doesn't vary.
 

lyner

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Well, yes. But, as it's a dodgy question in the first place, I interpreted it with implied words "try to". I assumed that you would have to be purposely driving yourself in some direction in order to move there at the same time as moving in time. I suppose I was in an inertial frame?

Time certainly has some awkward qualities and it is easy, whilst trying to address questions of this sort to get sucked into Science Fiction.

Having discounted the possibility of matter traveling backwards in time, there is also the notion of Information traveling backwards. That could be handy. But information implies energy and I think that the equivalence of energy and mass makes it equally unthinkable. There are many opportunities for paradoxes along the lines of shooting your grandad. Perhaps telling your grandad about contraception could have the same effect on your existence.


 

Offline that mad man

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As I stated in another thread in order to travel back in time you must first stop going forward. I used a car as an analogy?

You first have to come to a stop before you can go backwards and if that is the case then time would stand still and you would cease to exist. If that happens you would not be able progress any further back in time. The same I think would also apply to information.

There seems to be a barrier, similar to the speed of light, that you cant cross unless Dimensional time travel is possible.

No paradoxes arise as to me it seems an impossible thing to do just like going faster than the speed of light. If it was possible then we should already know as someone in the future would certainly have done it.
 

lyner

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time would stand still and you would cease to exist

Just to be difficult - for a photon, traveling at c, time slows to zero. That still exists.
 

Offline that mad man

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time would stand still and you would cease to exist

Just to be difficult - for a photon, traveling at c, time slows to zero. That still exists.

I thought that was just theoretical possibility based on relativity and qm which means its possible but not provable.

For a photon without mass maybe, but would that not then mean that any observer would also have to consist of photons in order to reach zero time? With an observer, a time traveller who consists of mass that could not happen.

At least I don't think it can.
 

lyner

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I did say I was being difficult.
 

Offline syhprum

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"to go backwards in time you would first have to come to a stop", this implies that time can be divided into infinitesimal periods.
Is this the case is it not quantitsed?.
 

Offline that mad man

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I did say I was being difficult.

 ;) :)
 

lyner

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"to go backwards in time you would first have to come to a stop", this implies that time can be divided into infinitesimal periods.
Is this the case is it not quantitsed?.
Hang on a bit. A turning value doesn't imply quantisation. A function could be continuous and differentiable throughout its whole range yet pass through zero.
 

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