speed of light and time

[herpguy]

According to modern mathmattics, if you go faster than the speed of light you will go back in time. This has made me think about a few things. (1) If you travel as fast as light will time freeze? (2) Is it possible to go at a negative speed? If so, would it fast-forward you through time? If you have any answers to my questions or more backround information, please reply.

[JPQuiceno]

heh, not to be rude, but do a search on this in the forums, more than 10000000 trillion threads on this.

[T-Nemesis]

Is there any true evidence to support the theory if you break the speed of light you will go forward through time or is it all just conjuncture?

[binosh1]

this is a confusing question like how big is the universe? its like can you actually go back in time? im a bit cynical on this and would say no and would lhave to see it with my own eyes to think otherwise.

[LazerFazer]

Is there any true evidence to support the theory if you break the speed of light you will go forward through time or is it all just conjuncture?

 

It seems like you're a bit confused about what happens as you approach c. According to Einstein's relativity' date=' your speed can never exceed c. As you go faster, your mass increases by the gamma factor, which turns to infinite at c. This, taken into account with F=ma, means that it would require an infinite force to accelerate you further. So, basically, if we can't get TO the speed of light, how can we exceed it? And as far as I know, relativity has been proved. Two atomic clocks were synchronised on the ground, and one was loaded onto an airplane and flown around the world. When the time the two clocks reported were compared, they were different. This difference was exactly what was predicted using Einstein's relativity equations.

 

The thing about 'going forward' in time also deals with relativity. As you increase your speed, time gets dialated, also by the gamma factor. So while you may experience only 1 year of time, people on the 'outside' might experience 20 years, and thus you would have 'moved forward in time'.

 

its like can you actually go back in time?

 

That's answered by mattasouths:

Going back in time is different you would need to have an imaginary number as your mass (number squared = negitive) which is seemingly impossible.

 

Cheers,

LazerFazer

[Meti]

There is a topic "Bendin the rules". My post contains an explanation and link that you may be interested in.

 

Hope this helps.

 

~Meti

[Twerpy]

Two atomic clocks were synchronised on the ground, and one was loaded onto an airplane and flown around the world. When the time the two clocks reported were compared, they were different.

 

Just out of interest, would i be right in guessing the one on the plane was slower? Also how much were they out? Off topic I know but i'm interested

[Meti]

The basic idea is that the faster an object moves spatialy, the slower it moves in time (for more details read my other posts - or my blog: http://www.writingup.com/meti). When the clocks were compared after the flight, both times were different, but both were also correct. The clock on the plane moved spatially faster than the one on the ground, so it marked time more slowly. So, if the Ground Clock says 10:01, the Plane Clock would say something like 10:00. Both times would be correct to each of the clocks, respectivly. Keep in mind, the example of an "atomic" clock is used because, unless the clock were moving thousands of mph, the difference would be extremely small; and only "atomic" clocks would be able to detect this difference.

[swansont]

Just out of interest, would i be right in guessing the one on the plane was slower? Also how much were they out? Off topic I know but i'm interested

 

FYI - It was four clocks, not one.

 

You'd be half right. One set ran, on average, 40 nanoseconds slow. The other set ran, on average, 275 nanoseconds fast. Quiz time: Can you tell which way each trip went? And why there was a discrepancy?

[Meti]

Well, I thought there was a bit off in that circumstance. I believe that when the plane carrying the two clocks moves in an eastward direction, it would be accelerating faster than the eastward rotation of the earth, moving faster relative to the earth's spin - and causing time to move slower. The inverse would be the reason for the time gain; the plane, traveling westward, in effect - slowing down relative to the earth - causing time to move faster. That should be correct, or - just about.

[swansont]

Well, I thought there was a bit off in that circumstance. I believe that when the plane carrying the two clocks moves in an eastward direction, it would be accelerating faster than the eastward rotation of the earth, moving faster relative to the earth's spin - and causing time to move slower. The inverse would be the reason for the time gain; the plane, traveling westward, in effect - slowing down relative to the earth - causing time to move faster. That should be correct, or - just about.

 

 

That's the gist. The earth isn't an inertial frame, and so its motion matters. All of the measurements have to be made with respect to an inertial observer.

[amrit]

you can not travel into past, because past exists only as a memory, see here: relativity: ATPS Theory, or file attached.

 

yours, amrit

 

3. Mathematical Time and Physical Time - EJTP.pdf

[Bettina]

Ok...help me please.

 

If a light beams top speed was 100mph (for example), and you were in a car traveling next to it at 50mph, when the driver looked at the light beam he would see light traveling at 100......not 50. This I understand.

 

An observer on a mountain witnesses the race and sees the light beam travelling at 100mph and yet sees your car travelling at 50mph. I understand this too.

 

I understand that the car driver doesn't feel any different. Everything in the car is normal to him....except he is confused.

 

The observer on the mountain looks thru a telescope at the car and observes that both the car, you, and everything pertaining to the car is compressed in the forward plane.....I understand this too....

 

My question is what form is the driver in....slow motion or stopped. Logic tells me that time has slowed to a stop for the driver which is why he sees light at 100. This last part I'm having trouble seeing.

 

Bettina

[DV8 2XL]

Slow motion to an outside observer, normal to himself. This is the idea of 'frames' in Relativity.

[sunspot]

If one had mass and attempted to reach C, this would be impossible, since mass would increase to infinity and would therefore require more energy to achieve than is in the universe. To travel at C, one would need to become pure energy. Even the smallest quanta of energy can travel at C. To go faster than C is currently considered impossible. Like matter, energy has a speed limit, which in this case is C. As such, to go faster than C would require that energy would need to change into something else. We do not know yet what this something else is or could be, and based on what we do know, C is the current universe speed record.

[yammers]

If one had mass and attempted to reach C, this would be impossible, since mass would increase to infinity and would therefore require more energy to achieve than is in the universe. To travel at C, one would need to become pure energy. Even the smallest quanta of energy can travel at C. To go faster than C is currently considered impossible. Like matter, energy has a speed limit, which in this case is C. As such, to go faster than C would require that energy would need to change into something else. We do not know yet what this something else is or could be, and based on what we do know, C is the current universe speed record.

 

 

Isn't there some evidence that photons have mass? albeit minute...

[yammers]

Disregard my above question...I found the answer in another thread. Thanks

[Bettina]

If one had mass and attempted to reach C, this would be impossible, since mass would increase to infinity and would therefore require more energy to achieve than is in the universe. To travel at C, one would need to become pure energy. Even the smallest quanta of energy can travel at C. To go faster than C is currently considered impossible. Like matter, energy has a speed limit, which in this case is C. As such, to go faster than C would require that energy would need to change into something else. We do not know yet what this something else is or could be, and based on what we do know, C is the current universe speed record.

 

Although your correct, I learned that the initial expansion of the universe was faster than c though it carried no information so I think that was the record....whatever that was.

 

Bettina

[□h=-16πT]

The rest frame of light is not definable.

 

Negative speed, no, as speed is the magnitude of velocity, a vector, and is thus positive. Velocity can be negative, if one defines what is meant by positive velocity.

[patcalhoun]

According to modern mathmattics, if you go faster than the speed of light you will go back in time.

 

In some frames of reference, a two dependent events along a space-time path may appear acausally.

 

This has made me think about a few things. (1) If you travel as fast as light will time freeze?

 

It's easy to show that it would not by looking at the interval. A null-like path in 1+1 dimensions is [imath]-dt^2 + dx^2 = 0[/imath]. Since photons are most definitely not at rest with respect to any reference frame, then dt cannot be zero.

[□h=-16πT]

It's easy to show that it would not by looking at the interval. A null-like path in 1+1 dimensions is [imath]-dt^2 + dx^2 = 0[/imath]. Since photons are most definitely not at rest with respect to any reference frame, then dt cannot be zero.

 

In it own reference frame we'd have

 

[math]d\tau ^2=0[/math]

 

The norm of its four-velocity would then be

 

[math]\vec{U}\cdot \vec{U}=\frac{d\vec{x}}{d\tau}\cdot\frac{d\vec{x}}{d\tau}=\frac{0}{0}[/math]

 

The rest frame of light is thus undefined.

[patcalhoun]

In it own reference frame we'd have

 

[math]d\tau ^2=0[/math]

 

The norm of its four-velocity would then be

 

[math]\vec{U}\cdot \vec{U}=\frac{d\vec{x}}{d\tau}\cdot\frac{d\vec{x}}{d\tau}=\frac{0}{0}[/math]

 

The rest frame of light is thus undefined.

 

Exactly.

[Connor]

This raises an interesting question to ponder.

 

What (assuming photons could see) does a photon see as it travels at the speed of light?

 

seems like length contraction would cause its "universe" to be two dimensional, with no depth in its direction of travel. Also, as it travels at the speed of light with respect to everything,everything would seem to be unmoving, wouldn't it?

[patcalhoun]

This raises an interesting question to ponder.

 

What (assuming photons could see) does a photon see as it travels at the speed of light?

 

seems like length contraction would cause its "universe" to be two dimensional' date=' with no depth in its direction of travel. Also, as it travels at the speed of light with respect to [i']everything[/i],everything would seem to be unmoving, wouldn't it?

 

You're performing a limit here, which doesn't change the fact that we cannot define a rest frame for a photon.

[amrit]

According to modern mathmattics, if you go faster than the speed of light you will go back in time. This has made me think about a few things. (1) If you travel as fast as light will time freeze? (2) Is it possible to go at a negative speed? If so, would it fast-forward you through time? If you have any answers to my questions or more backround information, please reply.

 

Amrit: nothing can go faster than light, a photon is mass less and has a speed of light, all mass particles are slower.

particles and bodies do not travel into time, their movement itself is time

 

Physical time (motion) is a physical quantity measured by clocks. With clocks we measure duration of the movement of body or particle regarding another body or particle. There is no still observer which can observe all the movements from a still stand point. All the movements are relative. This is the main insight of the SR.

According to the Mach Planck definition in a Planck time a photon pass Planck distance. Time is a movement of a photon into Planck distance. The movement of photon into Planck distance is a "smallest" movement possible in the universe.

Speed of time (motion) depends on the density of space:

see more: http://forum.physorg.com/index.php?showtopic=4321