TIME TRAVEL

B.O.B DOLE · 21 Dec 2005

This type of subject rattles my cage the scientist say if traveling faster than the speed of light you would travel back in time.
my point is why they dont know the speed of time.

AdamW · 21 Dec 2005

Sorry, I'm busy at the moment. Could you ask me the same question but 10 minutes ago please?

Time has no speed.

Speed is the rate of change of distance with respect to time. Hence "miles per hour", or "metres per second". You relate one dimension to another in order to determine what speed something has travelled through space-time.

Distance has no speed, time itself has no speed. It doesn't propogate through space, anymore than space propogates through time. It's just another dimension on a graph.

So, saying "what is the speed of time" is like asking "what is the speed of length?"

Hope this helps!

supersparks · 21 Dec 2005

there isnt a speed of time

its an instant thing, 1 second is how long it takes for us to move forward exactly 1 second no matter where you are on the planet, 1 second in the UK is exactly the same in new zealand and both if calibrated, would expire at exactly thye same moment.

B.O.B DOLE · 21 Dec 2005

AdamW said:
Sorry, I'm busy at the moment. Could you ask me the same question but 10 minutes ago please?

Time has no speed.

Speed is the rate of change of distance with respect to time. Hence "miles per hour", or "metres per second". You relate one dimension to another in order to determine what speed something has travelled through space-time.

Distance has no speed, time itself has no speed. It doesn't propogate through space, anymore than space propogates through time. It's just another dimension on a graph.

So, saying "what is the speed of time" is like asking "what is the speed of length?"

Hope this helps!

so time is a man made name to use as a measurement to measure time but if time does not exist how can it be measured

B.O.B DOLE · 21 Dec 2005

supersparks said:
there isnt a speed of time its an instant thing, 1 second is how long it takes for us to move forward exactly 1 second no matter where you are on the planet, 1 second in the UK is exactly the same in new zealand and both if calibrated, would expire at exactly thye same moment.

IF THERE WHER NO SPEED OF TIME and it where an instant thing why does it take the light from a distant star to travel to earth 500 years

so what you are saying nothing exist in the future has everything is now
but how can this be true if you break a second down you can break it down for ever and there will always be time such eg.

0000000000000000000000000000000000000.1 of a second

johnny_t · 21 Dec 2005

I'm not sure you go back in time, do you ? If you run faster than the speed of light, you can give the appearnace of having goe forward in time by arriving before the light from you does - You can look backwards and then watch yourself arrive (actually I guess it'll be something odder than that, as you will look back and see yourself running backwards away from you, as the light arrives at different times).

Relative time does change with gravity though. IIRC, there was a famous case in the '70s where some astronauts came back to earth and found they had travelled future to a time when Apes had taken over the Earth. Damn Them ! Damn Them All to Hell !!!

johnny_t · 21 Dec 2005

Actually, you wouldn't see yourself running backwards at all. You'd see like a film of what you did at T-1, then T-2, then T-3, etc. Which I suppose is a bit like going back in time. Its only really seeing the light from back in time though, rather than something you can interact with.

B.O.B DOLE · 21 Dec 2005

johnny_t said:
Actually, you wouldn't see yourself running backwards at all. You'd see like a film of what you did at T-1, then T-2, then T-3, etc. Which I suppose is a bit like going back in time. Its only really seeing the light from back in time though, rather than something you can interact with.

if that where so when we look at a star it looks normal and we are seeing it 500 years ago so the light we see is 500 years old but looks normal

johnny_t · 21 Dec 2005

Exactly !!

That's why the interest in building more powerful radio-telescopes. By being able to see further-off objects, you are actually seeing further back in time, and therefore can get some more clues as to what happened around big-bang time......

petewood · 21 Dec 2005

johnny_t said:
IIRC, there was a famous case in the '70s where some astronauts came back to earth and found they had travelled future to a time when Apes had taken over the Earth. Damn Them ! Damn Them All to Hell !!!

One of those astronauts looked remarkably like Charlton Heston if I recall correctly.

This type of subject rattles my cage the scientist say if traveling faster than the speed of light you would travel back in time.

I have not heard this, but I believe the theory is that as you approach the speed of light then objective time slows. This means that if a spaceship leaves earth and travels close to the speed of light (186,000 miles/sec) then an observer who could see both the earth and the spaceship would judge that time was passing slower on the spaceship, even to the extent that if two clocks were synchronised before lift-off then this observer would begin to see the 'earth' clock getting ahead of the spaceship clock, even though the people on earth and the people in the spaceship had no subjective indication of a change in the rate of passing time.

pickles · 21 Dec 2005

B.O.B DOLE said:
This type of subject rattles my cage the scientist say if traveling faster than the speed of light you would travel back in time.
my point is why they dont know the speed of time.

Time doesn't have speed it is a measurement that is only relevant to living things, no one can define exactly what time is or wehther it exists independently.

It is impossible to travel faster than light speed. It is an absolute limit, speed is limited by mass, light being a massless particle is the fastest thing, everything else having mass can only approach light speed to varying degrees. The point about time travel is that if you could travel at light speed, because time is relative to each observer it would appear to move differently to you ie faster or slower depending on who your travel is relative too........ Einsteins theory of Relativity

I'm explaining this really badly, but you need to be Albert Einstein to understand it properly.

The problem with this weird stuff is that several experiments have proved that time can actually run at different speeds. An experiment was done with atomic clocks (incredibly accurate to the nanosecond) one on earth, one on an orbiting space ship. the one on the space ship worked infinitisimally slower than the one on earth. Einstein also predicted that gravity would bend light, another one that has been proved by experiments during solar eclipses

read a book by Steven Hawking "a brief history of time"

kendor · 21 Dec 2005

petewood said:
I have not heard this, but I believe the theory is that as you approach the speed of light then objective time slows. This means that if a spaceship leaves earth and travels close to the speed of light (186,000 miles/sec) then an observer who could see both the earth and the spaceship would judge that time was passing slower on the spaceship, even to the extent that if two clocks were synchronised before lift-off then this observer would begin to see the 'earth' clock getting ahead of the spaceship clock, even though the people on earth and the people in the spaceship had no subjective indication of a change in the rate of passing time.

The experiment was indeed carried out using two atomic clocks and when compared one had gained a few micro seconds!

johnny_t · 21 Dec 2005

kendor said:
petewood said:

I have not heard this, but I believe the theory is that as you approach the speed of light then objective time slows. This means that if a spaceship leaves earth and travels close to the speed of light (186,000 miles/sec) then an observer who could see both the earth and the spaceship would judge that time was passing slower on the spaceship, even to the extent that if two clocks were synchronised before lift-off then this observer would begin to see the 'earth' clock getting ahead of the spaceship clock, even though the people on earth and the people in the spaceship had no subjective indication of a change in the rate of passing time.

Click to expand...

The experiment was indeed carried out using two atomic clocks and when compared one had gained a few micro seconds!

Wasn't the difference due to gravitational pull affecting the march of time, rather than speed though ?

Steve · 21 Dec 2005

B.O.B DOLE said:
eg.

0000000000000000000000000000000000000.1 of a second

now, look carefully at that. It transpires as 0.1 seconds, not a short time at all really, when you compare it to 00000000000000.00000000000000000000000000100000000000000000 seconds. Now thats a really short time.

notb665 · 21 Dec 2005

I don't get how time travel can be possible.

If you travel back in time to a time that has already past, to say, when your Nan and Grandad got married and watch them get married, then surely when they originally got married you must've been there in the first place because you are there now.

Unless it's like in Back to the Future when you could watch yourself from behind a rock or something. But then when do the two of you join up?

TIME TRAVEL

B.O.B DOLE

supersparks

B.O.B DOLE

B.O.B DOLE

B.O.B DOLE

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