96 replies to this topic

[antonT]

A couple of years ago I was sat in bed and this came to me:

Say one was going around a distant star and back to Earth in a spaceship. The clock in the spaceship once back on Earth has run say 12 hours slow to the one on the ground, thus the hands on the clock in the ship surely would have moved in slow motion compared to those on the ground just as human hands (and other parts) would have moved in slow motion irrespective of not being able to tell if one was moving or not. I know that onboard the spaceship in flight a second would still be a second but because of dialation that second would take longer to pass. So at the near speed of light the astronaught would be vitrually frozen in time..

Differential aging would ensure that cause and effect was not violated and that time travel could not occur. In fact time travel would be impossible.

Is this the falsification of Einstein's Theory of Reletivity?

[sepulchrave]

antonT, on 01 August 2012 - 12:03 PM, said:

Is this the falsification of Einstein's Theory of Reletivity?

Not at all.

Relativity ensures that time travel is not possible unless one can travel faster than the speed of light, and it takes infinite energy for an object with mass to just reach the speed of light.

[keithisco]

sepulchrave, on 01 August 2012 - 04:02 PM, said:

Not at all.

Relativity ensures that time travel is not possible unless one can travel faster than the speed of light, and it takes infinite energy for an object with mass to just reach the speed of light.

Only in Theory, it is far from conclusively proven.Possibly correct, no argument on saying possibly, but maybe only in our own Spatial Frame of Reference.

Then again, if Spacetime is proven, then there is nothing to suggest that in certain regions it could not bend back on itself to reconnect at an earlier point in time.

There is also no evidence to prove that breaking the Causality clause is actually correct. Could you shake hands with yourself in a later or earlier timeframe? Could you kill your father going back in time, but still be alive on return to the "future"?? Do we even understand the Philosophical constructs that bind us to a Linear progression of time?

Physics has made enormous leaps recently, but I cant help feeling that something is missing, something that we dont yet understand, or can even visualise, and that will actually restrict the truly huge leaps in progress that are tantalisingly close. IMO

Edited by keithisco, 01 August 2012 - 04:33 PM.

[antonT]

sepulchrave, on 01 August 2012 - 04:02 PM, said:

Not at all.

Relativity ensures that time travel is not possible unless one can travel faster than the speed of light, and it takes infinite energy for an object with mass to just reach the speed of light.

I have been led to believe that if one can show that everything in a frame of reference was indeed not  normal but abnormal then the theory of relativity would have been falsified. Is this correct?

The example I gave in my original post was that of a spaceship that had gone around a distant star and then back to Earth. The clock in the spaceship had run say 12 hours slow to the one on the ground. Surely the difference in the time of the clocks is proof that time ran slow during the journey and if time had run slow everything else in the spaceship would have run slow and not be normal as required by the Theory of Relativity. How can one say everything was normal in the FOR of the spaceship when fact dictates that everthing ran in slowmotion during the flight? Everything may appear normal at lesser earthly speeds but at speeds approaching the speed of light in space nothing could be less normal! The clocks prove this and if humans were on board they would prove it as well by aging less then those on the ground. These are hard facts which cannot be denied.

Yes everything appears normal when travelling at  insignificant earthly speeds but at near-light speeds everything slows up drastically irrespective of FOR - the difference in clocks prove this. Relativity is fine for the everyday world as we know it, but I feel it does not cater satisfactorily for very high speed conditions.

Surely if in the FOR of the spaceship everything was not normal, then The Theory of Relativity will have been falsified.

[sepulchrave]

antonT, on 01 August 2012 - 11:34 PM, said:

I have been led to believe that if one can show that everything in a frame of reference was indeed not  normal but abnormal then the theory of relativity would have been falsified. Is this correct?

Not really, unless by abnormal you mean ``mathematically inconsistent''.

antonT, on 01 August 2012 - 11:34 PM, said:

...Everything may appear normal at lesser earthly speeds but at speeds approaching the speed of light in space nothing could be less normal! The clocks prove this and if humans were on board they would prove it as well by aging less then those on the ground. These are hard facts which cannot be denied.

It is still ``normal''. The humans on board this spacecraft would notice nothing different; that is the point of the theory of relativity.

After all, how fast is the solar system moving? The entire Milky Way galaxy (Sun and Earth included, of course) could be whizzing along at 99.99999% the speed of light, and we would not be able to tell.

The entire theory of relativity is basically an extension of something we know very well in our daily life; the concept of perspective. Perhaps you are standing directly in front of a door. To you, the door appears large and rectangular. Now I am standing quite some distance away, and off to the side. To me, the door appears small and is shaped like a parallelogram.

Is this a paradox? Of course not! We know from experience how distance and viewing angle can change the size and shape of an object.

Relativity adds an extra facet to the concept of perspective; it is not only your relative position to an object that matters, it is also your relative velocity. And not just the shape of the object is affected, but also the duration of events.

Time is still somewhat different than space, of course: you can go backwards in space but not backwards in time, and we are all moving forwards in time (but perhaps at different rates).

So I could retrace my steps back to where you are standing and view the door from your perspective; but I can't relive events to get a different perspective of their duration.

The mathematical foundation of special relativity provides the basis for these concepts: we are all familiar with changing our perspective by conducting a trigonometric rotation (i.e. turning to face a new direction). To change our perspective in time we need to conduct a hyperbolic rotation, by changing our velocity.

[Rlyeh]

Maybe I've misread the theory of relativity, how does time dilation (a phenomena predicted by relativity) disprove the theory?

[Imaginarynumber1]

Rlyeh, on 02 August 2012 - 01:39 AM, said:

Maybe I've misread the theory of relativity, how does time dilation (a phenomena predicted by relativity) disprove the theory?

Obviously, it doesn't. I would think that if somebody were to disprove relativity it would take a little more work that "sitting in bed".
I think the OP just isn't understanding the perspective of one traveling a high speeds, as sepulchrave pointed out.

[Rlyeh]

Imaginarynumber1, on 02 August 2012 - 05:56 AM, said:

Obviously, it doesn't. I would think that if somebody were to disprove relativity it would take a little more work that "sitting in bed".
I think the OP just isn't understanding the perspective of one traveling a high speeds, as sepulchrave pointed out.

What I mean, isn't his "thought experiment" just an example of time dilation? I didn't read anything that suggested relativity was disproven in his post.

[Imaginarynumber1]

Rlyeh, on 02 August 2012 - 06:29 AM, said:

What I mean, isn't his "thought experiment" just an example of time dilation? I didn't read anything that suggested relativity was disproven in his post.

Yeah, it is. I don't understand why an example of something that proves relativity becomes an example that disproves it.

[antonT]

Rlyeh, on 02 August 2012 - 01:39 AM, said:

Maybe I've misread the theory of relativity, how does time dilation (a phenomena predicted by relativity) disprove the theory?

Surely one of the most important requirements of relativity is that everything is relative? If in the FOR of the spacecreaft travelling at the near-speed of light everything is not normal then the theory of relativity is falsified?

[Rlyeh]

antonT, on 02 August 2012 - 08:24 AM, said:

Surely one of the most important requirements of relativity is that everything is relative? If in the FOR of the spacecreaft travelling at the near-speed of light everything is not normal then the theory of relativity is falsified?

In this example time is relative to the travelers frame of reference, and as such passes normally to them.
The theory of relativity (or rather theories), describes various physical properties being related to ones reference frame, and the connection between space and time.

[antonT]

Rlyeh, on 02 August 2012 - 08:35 AM, said:

In this example time is relative to the travelers frame of reference, and as such passes normally to them.
The theory of relativity (or rather theories), describes various physical properties being related to ones reference frame, and the connection between space and time.

But time does not pass normally but in slow motion on board the spaceship. the hands of the ships clock are running slow - why shouldnt human hands (and other bodyparts) run slow?

[Rlyeh]

antonT, on 02 August 2012 - 08:40 AM, said:

But time does not pass normally but in slow motion on board the spaceship. the hands of the ships clock are running slow - why shouldnt human hands (and other bodyparts) run slow?

There is no normally. Only someone in a different frame of reference would notice the time dilation of the ship, however the person a board the ship would notice events outside the ship speed up.

http://www.phys.unsw...me_dilation.htm

[antonT]

Rlyeh, on 02 August 2012 - 08:47 AM, said:

There is no normally. Only someone in a different frame of reference would notice the time dilation of the ship, however the person a board the ship would notice events outside the ship speed up.

http://www.phys.unsw...me_dilation.htm

What is actually happening on board the ship's FOR is what would represent "normall".  The hands on the ship are running in "slow motion" therefore biological systems are running in slow motion, therefore everything in the ship FOR is running in slow motion.

[Rlyeh]

antonT, on 02 August 2012 - 08:55 AM, said:

What is actually happening on board the ship's FOR is what would represent "normall".  The hands on the ship are running in "slow motion" therefore biological systems are running in slow motion, therefore everything in the ship FOR is running in slow motion.

Yes it's running in slow motion compared to a reference frame of a lower velocity. Still there is no normal or absolute passage of time.