Time travel (Explain This To Me!!)

Originally posted by quiksilver
So if we could do this and with a solid object attached to the wheel or wateva what would happen(apart from the probability that the thing u attached might break, bend resistance etc.) ?

There is a similar gedankenexperiment with a huge pair of scissors. The solution is that the blades will bend and even the edges will not reach the speed of light. A full explanation can be found here at the Relativity FAQ.

Originally posted by outsider
I may be wrong here, but I thought a read an article within the past couple years that someone had done this at one of the particle accelerator facilities. (I'll try to find it - it may have been BS)

I can remember ever seen something like this in a book or a scientific magazine. If this was ever found, I think it would be on international news and in the papers.

yea i no about that thing, just wasnt sure if it applied to what i was saying.As far as im concerned, i beleive things can go waaay way WAY faster than the speed of light, i mean the universe is just to big for there to not be. It will probably be on the other side of the light speed barrier. I think that the speed of light may only apply for a certain type of matter,(e.g the ones we see everyday and we are customed to researching and discovering) but on the other side of the light speed barrier, things will still go faster, and will have extaordinary mass (not infinite because they wouldnt be ON the barrier) and as they speed up the lose mass as its converted into weightless energy),until they are another form of pure energy. ne thoughts?

There are theoretical particles called tachyons that are supposed to go faster than light. I don't think these particles exist, because they should give of enormous amounts of Cherenkov radiation if they are charged.

From this article:

Now another familiar relativistic equation is E = m*[1-(v/c)2]-1/2. Tachyons (if they exist) have v > c. This means that E is imaginary! Well, what if we take the rest mass m, and take it to be imaginary? Then E is negative real, and E2 - p2 = m2 < 0. Or, p2 - E2 = M2, where M is real.

You can now deduce many interesting properties of tachyons. For example, they accelerate (p goes up) if they lose energy (E goes down). Furthermore, a zero-energy tachyon is "transcendent," or infinitely fast. This has profound consequences. For example, let's say that there were electrically charged tachyons. Since they would move faster than the speed of light in the vacuum, they should produce Cherenkov radiation. This would lower their energy, causing them to accelerate more! In other words, charged tachyons would probably lead to a runaway reaction releasing an arbitrarily large amount of energy. This suggests that coming up with a sensible theory of anything except free (noninteracting) tachyons is likely to be difficult.

tackyons have mass to they would have extreme amounts of mass so they would suck their radiation back in to give it energy again so it cant speed up once it starts emitting radiation and stuff.

i think its all about perspective, if you were travelling faster than light, you not travellg through time, you time is going slower than that around you

You want tachyons to have such an amount of mass that electromagnetic radiation can't escape it? You mean that a tachyon is so heavy it acts like a black hole? First of all, I don't know if the General Relativity solutions for black holes are made to work with imaginairy masses, but even if it's possible we would see a lot of tiny black holes flying around making holes in objects. That would make them really visible, because the particles that are pulled in would send out a lot of light.

gavind5uk, that is what relativity is all about; how do things look from different inertial observers (persceptive)? One of the conclusions is that your time goes slower relative to your environment if you move relative to your environment.

It is impossible to travel a the spped of light :

The infinite energy argument
When Einstein wrote down his postulates for special relativity, he did not include the statement that you cannot travel faster than light. There is a misconception that it is possible to derive it as a consequence of the postulates he did give. Incidentally, it was Henri Poincare who said "Perhaps we must construct a new mechanics, . . . in which the speed of light would become an impassable limit." That was in an address to the International Congress of Arts and Science in 1904 before Einstein announced special relativity in 1905.

It is a consequence of relativity that the energy of a particle of rest mass m moving with speed v is given by


E = mc2/sqrt(1 - v2/c2)

As the speed approaches the speed of light the energy approaches infinity. Hence is should be impossible to accelerate an object with rest mass to the speed of light and particles with zero rest mass must always go at exactly the speed of light otherwise they would have no energy. This is sometimes called the "light speed barrier" but it is very different from the "sound speed barrier". As an aircraft approaches the speed of sound it starts to feel pressure waves which indicate that it is getting close. With some more thrust it can pass through. As the light speed barrier is approached (in a perfect vacuum) there is no such effect according to relativity. Moving at 0.99999c is just like standing still with everything rushing past you at -0.99999c. Particles are routinely pushed to these speeds in accelerators so the theory is well established. Trying to get to the speed of light in this way is like trying to get to the pot of gold at the end of a rainbow.

This explains why it is not possible to exceed the speed of light by ordinary mechanical means, however, it does not in itself rule out FTL travel. It is really just one way in which things cannot be made to go faster than light rather than a proof that there is no way to do it. Particles are known to decay instantly into other particles which fly off at high speed. It is not necessary to think in terms of the particles having been accelerated so how could we say that they could not go faster than light? What about the possibility of particles which might have always been going faster than light and which might be used to send information if they can be detected and deflected without ever slowing down to less than the speed of light? Even if such particles don't exist there may be ways of moving matter from A to B, faster than light can get there by the usual root, but without anything having to go at a FTL speed locally.


Or maybe it is possible?

Faster Than Light? Well �
PRINCETON, N.J. -- The dreams of warp drive and faster-than-light communications will have to remain just that. According to the scientists who have demonstrated superluminal group velocity, the reports of the death of special relativity have been greatly exaggerated. The group has found that the superluminal speeds it demonstrated in the lab can be explained with theories in accordance with relativity and are unlikely to apply to information carried by light.
In its report in the July 20 issue of Nature, the team at NEC Research Institute Inc. describes how it used laser pumping to excite cesium gas in a 6-cm-long, paraffin-coated glass cell to one of its 16 possible quantum mechanical states. A near-Gaussian, 3.7-�s probe pulse from a diode laser was injected into the cell and detected at the far side with a high-sensitivity avalanche photodiode. The researchers found that the peak of the light pulse emerged from the cell 62 ns earlier than it would have had it traveled the same distance through a vacuum. Effectively, it took negative time to make the journey, showing a pulse advance 310 times the vacuum transit time.
They attribute the effect to interference of the frequency components of the pulse as it passes through the gas. The excited cesium gas is a so-called anomalous dispersion medium that modifies light waves in such a way that, as shorter wavelengths enter the cell, they are elongated and longer wavelengths are shortened. When a wave exits the medium, its original wavelength is restored. Considering a pulse as a number of waves in phase, the effect of the gas is to bring the light's components back into phase ahead of where they would have been had they passed through a normal dispersion region or a vacuum.
Lijun Wang, a research scientist at the institute and lead author of the report, said his team's rough calculations show that the phenomenon seen in the smooth pulses does not apply to light conveying information. Citing Leon Brillouin's assertion that the speed of information should be understood as the frontal velocity of a step function on a pulse, the researchers believe that it may accelerate information transfer speeds up to c, but not beyond it. Wang said that his group, like that of Raymond Y. Chiao of the University of California in Berkeley in 1998, has demonstrated the effect in an electronic system, where typical speeds are far less than c.
Because the superluminal effect can be understood in terms of the wave nature of light, Wang stressed that it is not at odds with special relativity. "It is not our intention to claim that we have defeated Einstein's theory," he said. "Some members of the popular press have reported that we are rebels tearing down relativity, but this is not the case. The results are consistent with relativity."
The team plans to perform a similar experiment, using a small number of photons to see what effects anomalous dispersion will have. "We suspect that there is going to be additional noise," Wang said. "This will most likely reduce the signal-to-noise ratio, preventing a real signal being sent faster than c

( source: Daniel S. Burgess / www.photonics.com... )

Nothing can accelerate to the speed of light, but traveling the speed of light is not impossible.

speaking of time, i find it amusing that one could travel as many lightyears as earth is old and witness our planet's birth.

and speaking of light, at least we'll be able to teleport and use worm holes rendering light speed useless.

Whoa.... Lot of interesting discussion on time travel.
However.. Pick up a book called Hyperspace authored by Michio Kaku. Lot of interesting theories on time travel, parallel universes, time warps and higher dimensions. Too much to list here but an interesting read nonetheless. I believe time travel is possible. We as humans just haven't figured it out yet.. In time, someone will figure it out sooner or later and when they do the world is in for some big changes!

Two very interesting links for you people who want to know more on time travel:

freespace.virgin.net... - Just great!!!

epunix.biols.susx.ac.uk...

Enjoy reading!