Curvity and Faster then Light

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Introduction

Robert Boyd, a professor of optics at the University of Rochester wrote an article which states[1]:

"As the pulse enters the material, a second pulse appears on the far end of the fiber and flows backward. The reversed pulse not only propagates backward, but it releases a forward pulse out the far end of the fiber. In this way, the pulse that enters the front of the fiber appears out the end almost instantly, apparently traveling faster than the regular speed of light."

What's even more interesting is that they have a video which shows how the light is acting. <dhflashplayer>file=light.swf|width=213|height=197|path=http://danielfry.com/fileadmin/DanielFry/News_FAQ/%7Cflashvars=&image=http://curvity.org/w/images/light_snap.jpg</dhflashplayer>

What is striking is how closely the description and video match what Alan describes in his example when the observer has reached the planet and is now in a position to watch his faster than light travel to its completion[2]:

First, your position at the telescope as the observer. At this point Time is positive. Second, your position on the surface of the Earth. Here Time is also positive but has a negative displacement of four years. Third, your position in the Space craft. Here Time is negative, as demonstrated by the fact that you observe it flying backward toward the Earth, and all actions taking place within it occur in reverse order. This is, of course, due to the fact that the craft had a velocity greater than that of C and so was constantly leaving behind the light which was emitted or reflected from it. As you observe the craft from your new reference point, the last light which it emitted arrives first.

If you continue to observe for several years, you will eventually see yourselves build the craft and take off into Space. At the same time you can see yourselves in the same craft hurtling backward through Space toward the inevitable meeting point where the past and the future join to become the present. ... If you continue to observe the two craft, you will see that the one which is moving away from you is constantly slowing down, while the one coming toward you from the Earth is accelerating. At the instant in which the velocity of the receding craft reaches zero, the approaching craft will reach it, coincide with it, and both craft will disappear completely from your view.

Isn't what Alan describes exactly what Boyd's experiment is describing? This isn't the first time I've mentioned light that seems to go backward, but it is the first time I have put together that it is the same as the ship/telescope example that Alan puts forth.

And then further on when Alan is describing what will be seen from the planet when looking back toward Earth and the ship that took the faster than light journey, he says:

"Here, Time is negative, as demonstrated by the fact that you observe it [the ship] flying backward toward the Earth, and all actions taking place within it occur in reverse order. This is, of course, due to the fact that the craft had a velocity greater than that of C and so was constantly leaving behind the light which was emitted or reflected from it. As you observe the craft from your new reference point, the last light which it emitted arrives first." [3]

Hmm, interesting and light going faster than light is a new phenomenon:

"This is a breakthrough in the sense that people have thought that was impossible," said Raymond Chiao, a physicist at the University of California at Berkeley who was not involved in the work. Chiao has performed similar experiments using electric fields.[4]


Below is a section that I no longer think is true. Anything going faster than light is a apparition.

As Explained by Curvity

In Boyd's experiment, light can be seen in three different places at the same time - inbound to the crystal, leaving the other side and a reverse wave headed back to the inbound wave. The reason there exists three different perspectives of the same wave is because the wave is traveling faster then light in the crystal. According to Curvity, the light in the crystal is traveling into the past which is why the wave leaving the front of the crystal leaves before the inbound wave hits the crystal. It works like this:

Boyds experiment explained negative time.jpg
The diagram splits time and distance into three sections - Outside the crystal are sections A and C and inside the crystal is B. There is the inbound wave front (in section A), "back in time" wave front (in section B) and the remaining wave front (in section C). From our perspective, time flows from start to finish from the top to the bottom of the diagram, however the light, while traveling FTL inside the crystal (in section "B"), sees our time going backward.

Let us start with how time flows from the light's perspective. First it starts out in section "A" and then it hits the crystal at the first vertical bar. Once in the crystal represented by section "B", because the velocity difference between the light and us is FTL, it sees our time go backwards (i.e. the negative side of Curvity), hence as it moves through the crystal it moves upward in the diagram. Once it hits the B/C transition, it then enters positive time with respect to us, and heads off normally.

From our perspective, we see three parts of the same wave - the inbound wave(A), the back-in-time wave (B) which, because we see it travel in the opposite direction in time that it was created, it seems to go backward. (i.e. the last light it emitted at the boundary between B and C is the light we see first!) Then the outbound wave leaving (C), which is again moving in positive time but starting back before the inbound wave has even hit the crystal. The longer the light spends at FTL speeds, the farther back and for longer we will see the three parts of the same wave.

Of course, if there really is negative time involved in Boyd's experiment, then it leads to some interesting experiments. For example, what would happen if you block the back-in-time wave from meeting with the original? My guess is that you can't, because the light will know in advance the mirror is there - how? Because it goes back in time when it travels FTL, and sees the mirror before it seems to hit the crystal.

What if it was a ship that was going FTL and it exploded? What would an observer on earth see? Logic suggests the following answer - We would first see the original craft in positive time heading toward the point where it goes faster then light. Then at some point before it reached the point where it goes FTL, from seemingly nowhere at some distant point, an explosion would occur and debris would scatter. At the same time, but occurring in reverse, the ship would reassemble and it would then start traveling backward toward the point where the original ship went faster then light. At that faster-then-light point, it would combine with the original ship and disappear. The only thing that would be left would be the wreckage of the ship. Similar to Boyd's light experiment, the explosion would mark the transition between the "B" and "C" sections. For a time we would see three ships, the original ship, the "unexploding" ship heading backwards and the remains of the ship. The length of the time where time goes backward would depend on how long the ship had been traveling faster-then-light.

If the universe really works according to Curvity and time can go negative as in Boyd's experiment then we can use that to make a prediction In our universe, there might exist rare objects, where for a time, there exists three copies, the object before it was going faster then "C", the object returning to join up with itself and the object as it exists "now", assuming it slowed down to within "c" for us.

An interesting aside is that, suppose for an instance that things, specifically information, can go faster than the speed of light as Alan suggests. Then it should be possible with properly treated fiber optic cables to have trans-continental conversations without any delay. The side effect of having FTL fiber optics is that it would have an advantage over satellite communications.

Causality

Is it possible to go far enough back in time to kill yourself? We might actually be able to test a version of that question in the lab with an altered version of Boyd's light apparatus. It would be another form of useless machine that turns itself off, but with the quirk, it would do so before the light was transmitted.

The test setup would look like this:

Useless machine with light.jpg

The dotted lines are the light impulses and because both Crystal A and B are FTL, the light in them travels backward in time. This means that the light leaving both Crystal A and B would leave before the light arrived. The trick would be to make both Crystal A and B long enough such that even before the light from light source was created, the light from the end of Crystal B would hit the photo-diode switching off the light source.

Is that possible?

The length of each crystal A and B are like small time machines. In other words, the longer the crystals, the sooner back in time the backward wave (also creating the exiting wave) has to start in order to cancel out the inbound wave at the front of each crystal.

Let us run through the sequence of events: Before light is even being generated in the light source, if Crystal A and B were long enough, the wave would exit Crystal B headed for the photodiode, in order for the backward wave to cancel out the incoming wave bounced off the mirror. And the backward wave in crystal A would have to start soon enough to cancel out the incoming wave from the light source.

BUT, if the light leaving Crystal B hit the photodiode switch turning off light source A, could it do so before the light source had a chance to transmit? And if it can, did the light exist at all?

(caveat - Do we need Crystal B at all and why not just have a wire sending the signal back? They are equivalent, but you would need a Crystal A long enough that the returning signal appeared far enough ahead that the returning signal could get back to the light source before it left.)

Let us work this example to the extremes - what if a crystal was long enough that it took a year for the signal to travel back to the front of the crystal. In other words, a year in the future you transmit a signal you can see today. Would it be possible to have a signal leave even before you had setup the light source? Let us take the example even farther, what if the crystal was long enough that a signal took your entire life to travel its length? Could you transmit a signal before you were even born? And if so, what of free will? What if you decided not to transmit the signal, or died?

Causality and it's affects on free will is one of the big holes in Curvity. The great thing is that we might even be able to test it with variations of Boyd's experiments.


  1. "Light's Most Exotic Trick Yet: So Fast it Goes ... Backwards?", University of Rochester, May 11th, 2006
  2. "They Rode in Space Ships", Gavin Gibbons, Neville Spearman, 1957, pg 70
  3. Page 80
  4. "Light Can Break it's Own Speed Limit, Researchers Say", cnn.com, July 20th, 2000