A musing,

I heard it say that light (or whatever) can travel faster than the speed of light by warping (folding) space and bringing the destination closer to my departure point. This does not sound right to me at all. If we travel along the folded space we would still traverse the entire length of the folded space geometry.

But does warping (folding) of space have anything to do with speed? IMO it is a function of relativity.

Example: I travel along a road toward a destination. This destination lies 60 miles away along a curved path, and as it happens the sum of the curves in the road actually brings me closer to my point of departure than the actual miles traveled, by half (30 miles as the crow flies).  One could say that the road folded itself toward my destination. I travel this road @ 60 mph (fastest speed my car can travel) and it takes me an hour to reach a destination which actually lies only 30 miles away from my departure point (as the crow flies).
Now I create a shortcut, a straight road (as the crow flies), cutting directly toward my destination (cutting out all the curves along the path), and actually reducing the distance to be travelled by half. Thus @ 60 mph I arrive at my destination in half the time.

But this is not a result of folding space or speed, on the contrary, it is a result of creating a straight line shortcut toward the destination, bypassing the curves altogether.

When we create a travel plan, we often end up with directions which gives us a choice of routes, one being shorter but taking longer (by county roads restricting speed), one being longer but taking a shorter time (by freeway, maximum speed). Its all relative.

Any thoughts on this little visualization?

Count Iblis - 22 June 2011 11:00 AM

If you can send signals faster than light, you can build a device that allows you to send signals into your own past, see here:

http://en.wikipedia.org/wiki/Tachyonic_antitelephone

(the math is straightforward)

This leads to a paradox, because if you receive a phonecall on Sunday form yourself on Monday, then you can decide not to call yourself up the next day, while if you don’t receive such a phonecall, you call yourself up the next day.

Count Iblis - 22 June 2011 11:00 AM

If you can send signals faster than light, you can build a device that allows you to send signals into your own past, see here:

http://en.wikipedia.org/wiki/Tachyonic_antitelephone

(the math is straightforward)

This leads to a paradox, because if you receive a phonecall on Sunday form yourself on Monday, then you can decide not to call yourself up the next day, while if you don’t receive such a phonecall, you call yourself up the next day.

I believe that has been proved impossible. You cannot receive a phonecall from a person, before that person has picked up the phone and the call has been made.

I believe in Japan just such an experiment was performed by a scientist who actually risked his own life. The idea was if he could shoot himself from the past. Somehow, he created a window into the past. He openened the drawer, loaded the gun and then entered the window into his past, to try to shoot himself in the future. But when he looked at himself in the future he had not yet opened the drawer and loaded the gun which has was holding loaded and ready to shoot. If he had shot himself before had had a chance to load the gun, he could not possibly be holding the the gun to shoot himself with. Apparently he lived to tell of his experiment.

IMO one would have to fold space in such a manner as to end up behind yourself watching yourself make the phonecall, but that would not be travelling back in time, it would still be a forward movement in time but backward in space, but then would you would never be able to catch up with yourself, thus you would never be able to send the reply, and even the reply would never catch up with you.

IMO, if we could indeed find a way to travel back in time, we could never do so physically and be unable to affect the past. Perhaps as a non-physical observer?????  Wouldn’t that open a can of worms!!!

Write et al.:

There is often some confusion about relativity theory. events that are causally linked can never be or observed to be in any other order than they happened; the relativity of events only obtains when they aren’t causally linked. So for example, in no frame of reference is your birth observed after your first car purchase.

As for that japanese guy: it seems pretty far-out that anyone has travelled back in time, or even observed it in the relevant sense. The paradoxes and impossibilities you mention would still be present: molecules not present last Saturday would impossibly be present, light rays not intercepted that day would then also be intercepted, etc.

chris kirk

inthegobi - 24 June 2011 06:26 AM

Write et al.:

There is often some confusion about relativity theory. events that are causally linked can never be or observed to be in any other order than they happened; the relativity of events only obtains when they aren’t causally linked. So for example, in no frame of reference is your birth observed after your first car purchase.

As for that japanese guy: it seems pretty far-out that anyone has travelled back in time, or even observed it in the relevant sense. The paradoxes and impossibilities you mention would still be present: molecules not present last Saturday would impossibly be present, light rays not intercepted that day would then also be intercepted, etc.

chris kirk

I agree.

As I said, the experiment failed…...or should I say, it proved the impossibility…...