In 1905 Albert Einstein made a startling discovery, that the velocity of light is kind of a speed limit that no body with non-zero mass could cross. However, if the mass is very less then it could be accelerated to speeds very close to the speed of light. Imagine two astronauts in a spaceship in the Earth’s orbit. They have light clocks synchronized with one another. The clock is such that it has two mirrors, the up-side and the down-side. We leave a photon and let it travel between the two mirrors. To understand the case from our perspective we reduce the speed of the photon so that we can see it strike the two mirrors distinctly. The photon travels vertically up down. Now one of the astronaut (A) remains stationary in Earth’s frame and the other (B) goes round and round the Earth with increasing speed. B will see that the path of the photon of light clock of A will be vertical+translational which is a zig-zag path. At higher speeds the path will appear smoother until at speed close enough to c the path will tend to a straight line. Imagine he could travel faster than c. What would he observe? He will see the path that he saw earlier only that its direction is reversed? B is back into the past (of A). BUT as the laws of Physics rules the cosmos nothing can go faster than light. To make sense of the above discussion one has to find out a way to travel faster than light without breaking the law.

There are regions of space with immense gravitational fields-BLACK HOLES-which wrap the curvature of space-time so severely that nothing, not even light can escape from its intense pull. If black holes rotate (Kerr black hole) then along with it the region of the space-time near it also rotates in the same sense as that of the black hole (Frame Dragging). Now in the above discussion replace the earth with a black hole with astronaut A at a sufficient distance from it and B in the region where the fabric of space-time is ‘dragged’. Applying the restrictions to B, he can go at speed close to speed of light. From the frame of reference of A the total speed of B is actual speed of B+speed of the fabric of the dragged space-time > speed of light! If technology advances so much so that we can attain speeds close to speed of light it might actually be possible of one to travel into the past.

How are you imagining that such an astronaut would perceive the world around him as he moved into the past (I don't think that the situation you described would facilitate backwards in time travel, and so I ask you this to get you to clarify what process you are talking about here).

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Consider this. If you see the motion of the ceiling fan in flickering tubelight then as the fan attains it speed from zero to maximum there is an apperent motion of the fan that we see in the reverse direction after the fan has attained a particular speed. Same is the analogy here. Consider the Zig-Zag motion of the light as a wave. When B crosses the speed of light the direction of the wave reverses. Now what that wave actually is? Its the ticking of the light clock of A. Since the ticking of the light clock reverses the time of A, form the frame of B, time runs backwards. So B gets into the past of A. Here I have taken the concept of the light clock just for visual clarification. The light clock for example is the same as that of A's heart beat(which runs in the reverse direction)

No, Lorentz first proposed this in his papers and books in the 1890s.

That is only an illusion due to the 60 Hz flickering of the florescent lamp. It’s the same type of illusion we see in a movie film of wagon wheels or air plane propellers turning. If you get yourself a variable speed stroboscope you can play around with that effect with all sorts of moving and turning things.

To get round the effect in movies Wagon wheels were made with uneven spacing between the spokes.

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'The eye can only see what the mind is prepared to accept'

But, astronaut B can only travel near the speed of light in the reference frame of the dragged space time. From outside the reference, B appears slower to A, and A will always see B as being slower than B imagines himself to be.

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Numbers are not case sensitive. (me)

What was the reasoning behind this?

What I had learned is that at C you would gain infinite Mass and require infinite Energy. It would be kind of interesting to know why C is the speed limit. And what of Tachyons?

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If are having your morning breakfast over a cup of coffee and preferably with a sugar tablet for sweetening, you can have a pretty good idea of why speed B will appear faster to A than B's actual speed. If you rotate the coffee with a teaspoon and drop a sugar tablet in it the tablet will rotate in it along with the mass of the coffee. This tablet is at rest in the frame of the fabric of the 'coffee'. Imagine that the tablet has a magically small engine that could propell it in the coffee fabric. Then it will have some velocity in the frame of the coffee where it was originally at rest. If you look at the tablet from the top, what will be its speed. > or < its original speed. Certainly more than is original speed ie. its speed in the frame of the fabric of the 'coffee'!

Same is the case here. The fabric spacetime from where A is watching B is stationary. So the velocity of B will be its velocity in the refrence frame of the dragged space time + the velocity of the of the fabric of dragged space time.

c is the cosmic speed limit because as the speed increases the mass of the body increases by the relation [mass at speed v =m/(sqrt(1-(v*v)/(c*c))) where m is the mass of the body when it was at rest]. To increase the speed one has to apply more force and force is a physical quantity that is direclty proportional to mass of the body that is being accelerated. At v=c, m is infinite. So, we, or for that matter any catastrophic cosmological event such as supernova, should provide immense energy so as to create infinite force on the body or any fundamental particle which is just impossible. So speed=c is impossible. Speed greater than c is truly impossible. The above relation is a consequence of the conservation of linear momentum where we use the relativistic approach and take the lorentz velocity transformation into account.


About Tachyons. Tachyons may exist. If we can find a particle that can give off Crenkov Radiation in vaccume, its a Tachyon. According to relativity nothing can go faster than lights. The theory, however, does not forbid the existence of such particles with v>c ie. it does not exclude particles that travell faster than light. Thus Tachyons may exist. However in such cases energy would become imaginary. No such particle has been found thus far.

It appears what I wrote and what I was thinking don't match up.

"A will always see B as being slower than B imagines himself to be." should have been "A will always see B slower than B imagines A to see him as being"

Once again; I can picture it, but words fail me. Why do I try?

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Numbers are not case sensitive. (me)

Yes, in Lorentz theory the mass increases and would be infinite at light speed. Also, the length would physically contract in the direction of motion to being completely flat.

This is an electrodynamics theory he worked out with Maxwellian electrodynamics with the “ether” being considered. With Lorentz theory, it is the “ether” that puts up a resistance to the motion of atoms through it causes the effects and restricts the speed limit of particles to “c”. Lorentz treats the "ether" as if it were some kind of "field".

With the general late-19th Century “ether” hypothesis, the ether was fixed with a fixed universe, and most of the stars were fixed too. Only the planets, comets, and moons moved, and it was their motion through the “ether” than caused the electrodynamic effects suggested by Lorentz.

The electrodynamics part of Einstein’s SR theory is basically his addition of his own ideas to Lorentz theory, and the “kinematical” part was Einstein’s way of trying to do away with the need for an “ether”.

Maxwell let them in on the joke early on. If you reached the speed of light, what would keep you altogether.

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For those inclined to oppose human meddling with the structure of the universe or the composition and configuration of objects and groups of objects within the universe, consider:
Whether there is a limit to the magnitude of a modulation of chaos below which order remains invariant? Or, is order but a fiction invented by perspectives applied over finite, however large, time intervals?

If you could travel faster than light just for example oif you could.... wouldnt you need some sort of sheilding?? Travelling at (or close to) light speed would rip a human or a ship they were in apart right???