Why they say if we can travel faster than the speed of light we will be able to travel in time?

As you say traveling faster than the speed of light is impossible. It is also impossible for any mass to travel at the speed of light although approaching the speed of light is practical. As a mass approaches the speed of light a time dilation occurs. One twin (in a spaceship) approaches the speed of light and returns to earth. He is no longer the same age as his twin (as indicated by his atomic watch and perhaps his calendar too). However neither twin grows younger. Photons travel at the speed of light but have no mass. As more energy is provided to a photon (depending upon how it is released by matter) its wavelength shortens and it becomes more energetic and penetrating. UV light can penetrate thin clouds and give you a sunburn while X-rays with shorter wavelengths can penetrate skin and bone and gamma waves with the shortest wavelengths can penetrate lead to certain depths. Therefore if you supply more energy to photons they still travel at the speed of light (not faster) and merely have shorter wavelengths. Because speed causes a time dilation, a photon (at the speed of light!) does not age. The speculation follows that if matter and photons age more slowly with speed (and not at all for photons) going faster than the speed of light should reverse time.

1st, I recommend you read Brian Greene's "Fabric of the Cosmos" and "The Elegant Universe," because I will rely on my reading of both to tackle your question in brief. Greene points out that you can think of every moment of your life as though you're moving in two dimensions: space and time. Einstein of course showed us that time and space are interwoven, they are not separate, there is only spacetime, not SPACE and TIME. Now, if you are standing still, as I am writing this (er, I mean typing, LoL), then ALL of your velocity (the measure of motion) is through time...that is you are only changing your position in time during every interval of time. If you begin to move around, you are diverting some of your velocity into changing positions in space, so you are not "travelling" through time as fast anymore. Per Greene's book, consider Bart Simpson on a skateboard, if he goes straight at 100 m/s, then all of his velocity (100 m/s) is in that direction, lets call it North-South (he's on the highway). Now if Bart we're to travel at the same speed of 100 m/s but at an angle, then some of that 100 m/s velocity is in the East-West direction, and he has LESS THAN 100 m/s velocity in the North-South direction. This is because Velocity is a vector, and I am specifically considering velocity, not speed. If Bart wants to maintain a Velocity of 100 m/s North-South, he must INCREASE his TOTAL SPEED...so Lisa would have to measure Bart's Velocity as 150 m/s (or so) in a NW direction, in order for Bart's PURE NORTH-SOUTH VELOCITY TO REMAIN 100 m/s, as it was when Bart was going straight (Pure North-South). The speed of light is like a proportionality constant between motion through space and motion through time. As long as your speed is appreciably below lightspeed, your motion through time is unaffected (it doesn't slow down noticebly). But if you start moving at speeds that are a significant proportion of lightspeed, say 75% of lightspeed, then you're causing a noticeble change in your motion through time, your velocity thru time is slowing down. Now moving AT LIGHTSPEED, is the limiting case where your velocity thru time is v = 0 ("Photons do not age"). Velocity is a vector, and can have a negative valuse, it just means that motion is in a direction opposite to that wich is considered forward. So....If motion thru space AT c, is motion thru time = 0...then motion thru space at speeds above c, gives you negative values for motion thru time. Indicating that moving at a velocity greater than light, by any amount, will produce a motion thru time that is opposite of what we consider forward. One thing I didn't mention yet cause it is simpler to just present all that up there 1st, is that I always mean LIGHTSPEED motion thru space, or LIGHTSPEED motion thru time. This is the funciton of the C. The velocity of electromagnetic oscillations. Bart may have diverted some of his 100 m/s velocity from the N-S direction, into the E-W direction, but he NEVER diverted any of his lightspeed motion thru time, into lightspeed motion thru space. And hence he was always part of "our time," or "now." He didn't time travel. That is why we say the effect is not noticeable unless we deal with significant percentages of lightspeed. An equation we could use: Velocity (SpaceTime) = C (Velocity Space) x (Velocity Time) = C (Velocity of Light) Therefore: C (Vel. Light) / (Vel Space) = (Vel Time) And we see that as your velocity thru space increases, your velocity thru time goes down...but only when your (Vel Space) is significantly close to (Vel Light), will your (Vel Time) be less than 1, a decimal.....you see that, Vel Space has to be more than 3.0x10^(8) m/s in order for the RATIO to be less than 1. (3.0x10^(8) m/s) / (Vel Space) = 1, when (Vel Space) = C = 3.0x10^(8) m/s Now this leads us to say that our normal experience of passing thru time (?) is actually the experience of passing thru time AT LIGHTSPEED. There's something to think of.

Let's be clear about something. That is not at all what Einstein said. To go faster than the speed of light would require imaginary mass. Imaginary mass has no physical meaning as far as we know. Therefore traveling faster than the speed of light has no physical meaning. What I wrote about is implied by what Einstein wrote. He just derived that relationships between space and time.

supposedly, light is the ultimate speed barrier. it's the limit. So if you pass it, you will almost stay still while everything passes around you. Yes its confusing to a lesser mind than teh great Einstein! oh, and c=the C onstant speed of light

In the vicinity of higher mass time slows. As you speed up your mass increases. At the speed of light you should weigh infinitely and time should stop. Take it a step further and it's thought by some that you go in rewind.

I agree with your frustrations. I think what is not readily appreciated is that c is a barrier, beyond which no particle with mass can cross. c itself is an asymptote which defines the speed that a massless particle MUST go. The equations work when you place t by -t in the same way that cos(t) is symmetric about the y axis. So you could play on the other side of the light speed barrier and all the same equations work as they do normally except that time runs backwards. In our world, we are subject to the experimentally observed laws of thermodynamics and causality which would either need to be side-stepped or violated to observer time-reversal. Mathematically, there is a whole world of negative time on the other side of the light barrier. There are grave problems actually crossing that barrier, and if (somehow) that were to ever happen, then numerous paradoxes would need to be avoided. For example, the many-worlds theory could be invoked to allow someone to travel to the past but be forced into a new universe to avoid problems with causality. There are also many equations which describe physical processes which work just fine if you replace t by -t. This is what is meant by 'time symmetric'. While that's true, I don't think it automatically follows that information can travel back in time. At the quantum level, FLT events can and are used to explain (for example) quantum electrodynamics where individual mathematical components of the theory can invoke negative time to explain macro observations to a high degree of accuracy. For example the interaction of a proton and electron might be explained by another electron which can 'see the future'... or you could postulate the existence of a positron which is an electron with positive charge, and compensate by flipping -t back to +t. The theory works whether you use the positron idea or negative time but for a model of reality my money is on the positron. :-) ( e.g. the PET scan! ) Also, at the quantum level SRT seems to be violated for very short times which would violate conservation of energy but for the fact that the events 'borrow' energy from the quantum vacuum which gives rise to the sudden appearance and disappearance of 'virtual particles' such as surrounds an electron. The reason we measure time using c is because c is only possible when the mass of the thing is zero, and light is a massless disturbance in the electromagnetic field. A photon is the carrier for the electromagnetic force. Time is the passing of an event, and to observe that, energy must be moved from one place to another - the clock face to your brain for example. The fastest that a signal can travel is c.

We don't know what mass is, and we don't fully understand space-time. There could be layers of space-time where FTL (faster than light) speed is possible. The cap on speed in our local universe may be there so material does not leak out on its own. If it wasn't there we might see things start disappearing. But there is no reason why one cannot travel in dimensions that are beyond our current understanding. Space-time has a limited definition, and that's what people are adhering to now. I believe that light speed barrier will be breached when we are able to investigate how vibration changes a material.

Physicists who studied possibility of time travel do consider traveling faster than light, that would require infinite amount of energy for bodies with mass. They consider distorting space-time to create a shortcut between two regions of space-time. The regions are connected by a wormhole. Thorne, a theoretical physicist/professor, actually designed a time machine that does not violate the laws of physics. It means his time machine is theoretically feasible but of course impossible to build with our present technology.