Time travel possible.

[dmb]

If that were so, then you would have different measurements for light speed in different directions of space, which can not be true.

You have to have the same measurement in all directions.

If that were so, we would measure light traveling at various speeds depending on direction, while being on earth, because earth is constantly changing net speed in one direction.

Okay...

So say there was some type of detector that could measure the speed of a single photon without altering it's direction or speed. You place one detector on a post in the ground, another on a car which is to drive towards the post, and another car that is to drive away from the post. Each detector would record the same speed for that single photon, irregardless of the speed and direction of the detector was moving, right? It wouldn't make sense if that were because the photon was slowing down or speeding up between detectors to exactly counter the effects of the detector's speed...that implies some kind of exchange in information between the photon and the detector it has yet to hit. So could it be, because space is not absolute, that the cars weren't really moving at all in relation to some point in space agreed upon by the source of the photon and the detector, but they were moving in relation to some point in space agreed upon by each driver? That must have been considered by someone else before me...is there any reason to believe it is incorrect?

Edited October 19, 2007 by danemburke

[northwest]

I'm not sure I got your question right...

but in regards to moving detectors of speed of light, it would go like this:

let's forget about detectors, and say both the viewer and driver have eyes everywhere, or they have an army of observers

that instantly know what is going on everywhere in the universe.

that way, we don't have to take Doppler effect into account, and simply concentrate on distance light actually travels in a time interval

So, one man is standing on the ground, and the other guy is in the car, driving at 0.5 light speed.

So, to simplify things, both of them are omniscent (just so we don't have to take into account how late is some information when it gets to the observer)

The man on the ground sees a car traveling at 0.6c, speed traveling at c in all directions, and light distancing from the car at 0.4c in front of the car, and at 1.6c behind the car relative to the car.

That's pretty much common sense

And now relativity comes into play:

the man in the car is seeing this:

light is traveling in front of him at c (not 0.4c), light traveling behind him at c too (not 1.6c)

[Pierce8]

To those who hardly understand how time travel works by just reading some explanations found here..... i found an interesting site which has an animations of how this possible(timetravel).

http://www.pbs.org/wgbh/nova/time/think02.html

[Cebrakon]

That's what I thought, but as Northwest and Camlax pointed out, there is no "universal absolute" time. So time is relative to each observer. To the observer on earth, the spaceship occupant who left and traveled at lightspeed for a year, upon returning home would (to the earth observer) have aged less than he/she. True that what we see in sci fi movies is misrepresented/exaggerated, but there is no denying the fact of actual time variance. In case you hadn't read it, here's an interesting article on time variance and GPS satellites: http://metaresearch.org/cosmology/gps-relativity.asp

Quantum mechanics requires a universal absolute now. Also, special relativity requires time to be an imaginary number. A continuum of imaginary numbers does not allow time travel. Time is also imaginary in the ordinary sense of being something created by the mind, out of memories of past cycles and expectations of future cycles. The time variance used by GPS satellites is also quite real. When you do calculations with complex numbers, such as space-time, the imaginary part affects the final outcome, since to square it, or raise it to any even power makes it an ordinary real number, but negative in sign. I don't have any problem with any of the applications of relativity. I just want to point out that those GPS satellites never disappear into the past or future. They are always in the NOW. There is no reality to a physical past or present.

~~~Cebrakon

[Strange F8]

Quantum mechanics requires a universal absolute now. Also, special relativity requires time to be an imaginary number. A continuum of imaginary numbers does not allow time travel. Time is also imaginary in the ordinary sense of being something created by the mind, out of memories of past cycles and expectations of future cycles. The time variance used by GPS satellites is also quite real. When you do calculations with complex numbers, such as space-time, the imaginary part affects the final outcome, since to square it, or raise it to any even power makes it an ordinary real number, but negative in sign. I don't have any problem with any of the applications of relativity. I just want to point out that those GPS satellites never disappear into the past or future. They are always in the NOW. There is no reality to a physical past or present.

~~~Cebrakon

So then my original thoughts on this are more correct. If we were sitting in the same room and one of us had the ability/technology to accelerate their time frame/flow, then the person who did the time acceleration would appear to the the other as simply sitting still - barely moving, or not at all. The one who remained in the original time flow would appear to the person who had accelerated as moving somewhat faster or extremely faster than what they are experiencing. Perhaps this is like where 2 gears of different sizes meet. The point of meeting would be the "now" they both experience, but each one would be moving at speeds different from the other.

As for retro time travel, although it may be a mathmatical possibility, I'm beginning to think it is probably not possible in an actual physical sense (perhaps in a metaphysical sense however, but thats a topic for a different forum).

[dizzaN]

If time travel is possible, dont you think we would of met people from the future?

Peace.

horrid post.