# Speed of light and time travel

1. Feb 3, 2012

### morfin56

If it is true that when traveling close to the speed of light makes you go forward in time.
Then do you go back in time (observed from the destination) as you travel to your destination close to the speed of light?

And why don't particles traveling at near light speeds appear to warp time unless there is in fact a constant equation demonstrating that the particles leave going forwards in time and arrive coming backwards to present time.

I just watched Carl Sagan's Cosmos and my mind is filled with questions that google can't help me with.

Last edited: Feb 3, 2012
2. Feb 3, 2012

### ghwellsjr

Observed from both the point of departure and the destination, time goes slower for you the faster you travel. You never go backwards in time.

3. Feb 3, 2012

### morfin56

Ahh I see now, Thank you.

4. Apr 1, 2012

### aftermath

traveling forward is impossible except returning from a destination in the past. when returning from the past you can only travel to the exact time, within a millisecond, of the time you left. you could be gone, in the past, for a very long time but the time of your departure would not move forward. every person in the room would be standing in the exact same position as when you left. they would only see a bright flash of light. when you return, no matter how long you have been gone, you would be the exact age as when you left. you would not age. also, the time space continuum has nothing to do with time travel. to explain why you cannot travel into the future, you need an exact reference point. a date, time, co ordinance and event.

5. Jun 8, 2012

### biggleslife

Time travel is impossible using a faster than the speed of light scenerio. What is being observed is the light particle (photon) and not the actual event as it WAS happening. Traveling close to the speed of light would not slow down time, but your observation of the light particles will give you a visual of the event as though it was happening in slow motion. That is only possible to observe if you are going in a straight line.
At the speed of light you should observe the photons moving around each other as they travel in a straight line until they interact with other particles (atoms).
You would hear the event in an odd way I would imagine also. Since sound travels at a slower rate than light. Plus doesn't travel as far either. That is if you could somehow survive going that fast.
If an event happens and right as it happens you somehow are able to travel faster than the speed of light. All you will accomplish is traveling faster than a light particle (photon), and not traveling through time.
Interestingly our brains live in the future but observe the past. When the light particles (photons) enter our eyes and send signals to our brains we lose thousandths of a second. To compinsate we will take bits of information from our past to crystalize an image and action so we can respond to it.

6. Jun 8, 2012

### Staff: Mentor

According to SR, you can't travel into the future within your own frame of reference, but you can travel into the future of other inertial frames of reference, and of the denizens within these other frames of reference. An example of this is the Twins Paradox.

Chet

7. Jun 8, 2012

### aftermath

there is no example known to us at this point and time. we only have theories. travelers have spoke of particle separators and re-generators. traveling in to the future is impossible. as I told you, you can only travel in to the past using a specific time, co ordinance ie latitude and longitude and an actual event that happened at that time and place. once in the past you can only travel back (forward) to the exact time and place of your departure. you cannot jump time forward.
the grandfather paradox and the twin paradox is only theory and is, well, another discussion.

8. Jun 9, 2012

### ghwellsjr

You don't consider the Hafele–Keating experiment to be an example of the Twin Paradox?

9. Jun 9, 2012

### HallsofIvy

Actually, we are always traveling into the future, whatever our speed. Moving at speeds close to c, relative to observer A (never forget that condition) means that our experience of time will be slower that observer A so that we are moving into the future faster relative to him.

10. Jul 20, 2012

### biggleslife

True we are constantly traveling into the future, but speed does not have any influence on time. All you will do is travel from point a to point b on a plane faster than if you were not moving at all.
Time is always constant. There is nothing that can change time. There is no time travel. what you observe is the light particles (photons). So the observers can only observe the particles of the event. Not the actual event. So it would appear as though you are experiencing events in the past by traveling faster than the speed of light, but what is really happening is you are experiencing the particles that were a result of the event.
You have to take the observer out of the equation. Space and time is infinite. There is no value to them. Only the value we put on them.

11. Jul 20, 2012

### Mark M

This makes absolutely no sense. Time dilation and length contraction are well documented phenomena.

12. Jul 20, 2012

### rorix_bw

Can you explain specifically what you mean by that. How do you explain the Twin Paradox or the need to adjust clocks on a satellite ?

13. Jul 20, 2012

### biggleslife

Those are well documented from an observational stand point. The problem is that you are not adding variables like the force of motion on the moving object compared to the stationary observer.

14. Jul 20, 2012

### Drakkith

Staff Emeritus
What is the "force of motion"? I've never heard of such a term before.

15. Jul 20, 2012

### ghwellsjr

Do you disagree with Special Relativity?

16. Jul 20, 2012

### bcrowell

Staff Emeritus
It sounds like you need to learn some relativity. A good place to start is Relativity Simply Explained, by Gardner.

17. Jul 20, 2012

### biggleslife

I know relativity. Thing is does everyone else? Relativity is a theory and will stay a theory because it is based off of the observer, which should not be an equation.
The Twin paradox is not an actual test, but a way to give an example of how relativity works. The problem is that none of those have been tested.
Satellites using Atomic Clocks work because we know how atomic clocks BEHAVE when they move through space. Since the clock is moving at such a high speed there is going to be some changes on the sub atomic level thus changing the speed at which the atoms in the clock behave. Doesn't mean that the clock is going slower, but rather the way we measure changes due to its movement.

18. Jul 20, 2012

### Mark M

None of these have been tested? Oh really? Are you confident about that?

http://math.ucr.edu/home/baez/physics/Relativity/SR/experiments.html

19. Jul 20, 2012

### ghwellsjr

What about the atomic clocks at Greenwich near sea level compared to the similar atomic clocks at Boulder, Colorado at a much higher elevation? How do you explain their different tick rates?

20. Jul 20, 2012

### biggleslife

Greenwich study shows that Atomic clocks are only accurate if it is at a constant. Once it changes (moves) it changes the way it behaves. Thus giving you the ability to predict what it will do. The change in time to it is the way it operates at the atomic level.
Please pinpoint the studies that have proved that Special Relativity is true. I'm pretty sure all tests have to use some sort of rule or change to make it true.

21. Jul 20, 2012

### biggleslife

Stop thinking of light as an event and stop putting an observer into the equations.

22. Jul 21, 2012

### Drakkith

Staff Emeritus
No, you are 100% wrong. There are NO changes in the way it operates at ANY level.

Here are a few: http://en.wikipedia.org/wiki/Tests_of_special_relativity
As for using a rule of change to make it true, I have no idea what you even mean by that. The theory makes predictions that something should happen and we can test and see if that prediction comes true. That is called an observation or experiment.

Show me a single equation that has an observer in it. You won't find any because an equation is a mathematical entity. An observer is simply an object who's perspective we are doing the math from. This could be a person, an atom, an electron, whatever.

Apparently you don't even know what a scientific theory is. I highly recommend looking up the definition. Relativity will always stay a scientific theory because it IS a scientific theory. Theories do not "graduate" or get "promoted" from theory to something else. They always remain a scientific theory.

We haven't used actual twins because the difference in aging is so small for any possible tests that we could do that we would never be able to tell. This is why we use atomic clocks. They are capable of the precision required to measure the difference. Whether we use a person or a clock the twin paradox remains exactly the same.

Again, this is incorrect. The rules of physics do not change just because an object is moving. A moving satellite has every right to say that it is US who are moving instead.

Biggleslife, your knowledge about physics seems to include gaping holes in basic knowledge. This is ok, and you aren't the first to come here like that, but if you continue to make absurd statements and insist that you know things that aren't true then you WILL be banned.

23. Oct 9, 2012

### PunchyRascal

I was thinking about this topic and couldn't help but to realize that you can actually, in the popular meaning, travel in time. The twin paradox proves that in its essence. When the traveling twin comes back to Earth, he actually comes to the future Earth, from his point of view, him being only fraction of the time that passed on the Earth older.

So forward time travel is possible. Correct?

24. Oct 9, 2012

### ghwellsjr

Yes, but which twin are you saying is the one that travels forward in time? Aren't they both, just at different rates?

25. Oct 9, 2012

### PunchyRascal

Yes, yes, that is quite mind-blowing actually, that we all in fact travel in time all the time (travel in time all the time? :D) But I meant of course the traveling twin being the time-traveller.