Gravitic antitelephone?

Belial666 wrote:What if the whole "frame of reference" thing was an illusion of perception? Would FTL communication be possible then?

*Frame of reference is an illusion of perception.

**Yes, FTL communication would still be possible. Its contents may bewilder you, since you are lost. (in your frame of reference) But it isn't.

**Of course, reality can dream up a scenario that would throw a monkey wrench in those plans.

For example, you got a train car. In each end of the train car, you got a high-accuracy clock. In the middle of the train car, you got a device shooting a laser beam at each clock.
For an observer riding the train, both laser beams cross the same amount of space, hit both clocks and destroy them; the last recorded time given by both clocks is the same.
For an observer not riding the train, the train car is moving. The beam shooting towards the back of the car has less space to cross and arrives first, while the one shooting towards the front has more space to cross and arrives second. the last recorded time given by both clocks would not be the same.



However, once the train stops and the outside observer can actually see the recorded times, they happen to be identical, no matter what the outside observer saw happen.

Certainly! You are at a loss for the visual light speed communication of what you think you saw. You are lost within your own frame of reference(and to your local physics). The frame of reference for the outside observer is in constant flux with the source and per the oddity of time dilation. Goes to reason.

*The mechanics of the physics of the external frame of reference is affected by time dilation and Lorentz contraction -Variables that the senses fail to apply "on the fly." (npi) (Thus, intuitively lost to your own frame of reference.)

****** *

Time dilation in itself is a very interesting phenomena.

Taken handily off the web...

What is the time dilation relative to a outside observer if you were going at 99.9999999999 percent the speed of light?

in what follows, please consider sqrt() the square root function, and sqr() the square function (sqr(x) = x * x).

Let's suppose we have a bus, that is travelling at 99.9999999999% of the speed of light (let's call it c, which is more or less 3e8 meters/second)

Let's suppose further that the bus is 3 meters high.

Let's suppose we have a beam of light travelling from the floor of the bus to the ceiling.
If I'm going inside the bus, I'll see the beam reaching the ceiling in some time t.
This time would be t= 3/c.

For an outside observer, s/he would see the same beam performing a diagonal trajectory, rather than a vertical, like me.

From the outside observer's point of view, we have the beam travelling with a speed that has both a vertical and an horizontal component. The horizontal one would equal bus's speed which is (0.999999999999 * c).
But Einnie proved that the beam speed is always constant and always equal to c, both for me and for the outside observer. So, the vertical component of the speed of the beam would be sqrt(sqr(c) - sqr(0.999999999999 * c)), according to Pitagoras Theorem Let's call it cy
As the bus' heigth is 3 meters we have that for the outside observer the time that the beam took to reach the ceiling would be 3 / cy, or
3 / sqrt(sqr(c) - sqr(0.999999999999*c)).

The ratio of the outside observer time to my time will be c / (sqrt(sqr(c) - (sqr(0.999999999999 * c))

if we consider c = 3e8, we'd have this ratio equal (if I computed correctly) to 707106,78118672430109614106527721.

For me, one day in the bus would mean 707106,78 days for the outside observer, or
1935,9528 years. Almost 2 milleniums...

Note:
I have not checked the math here. It seems correct. Also note that the person hails from a culture that uses commas in place of periods in numeric symbols.

cthia wrote:

SWM wrote:I'd like to discuss this further, if it won't bore the rest of the forum to tears.

Exactly what disagreements do you see between us regarding travel through hyper? Or FTL? I haven't noticed any disagreements on either of those.

Of course you remember an area of disagreement. Hyperspace travel is a theoretical construct, relied upon heavily in science fiction. There are varying "distortions" of the physics to explain FTL travel.

It is generally agreed that maneuvering in hyperspace may or may not be possible. You believe that it is possible. I do not.

We both have detractors on our particular view. That's ok.

SWM wrote:
I don't see any point of disagreement. I never talked about the existence of hyperspace in the real world, only in the fictional Honorverse.

My apology. From one of our fairly recent exchanges, apparently I misread your post out of context. Consider this post a printed retraction.

The main point though, is there are two sides of the can/can't maneuver while in hyper. My math tells me no. However, as I said, there are detractors to both views.

Good to know that you are on this side of the fence of that.

And ... welcome!

Perhaps Duckk will some day incorporate support for MathML or HTML5 for these discussions to not be such a pain, and to motivate one to delve deeper. I find it extremely difficult to argue certain points without being able to "show the math." And I find myself straying away from certain discussions because of it. (That and a total lack of time. ("Join a book discussion forum Uncle/brother . That won't take so much of your time or focus." HA!))

My niece balked about that so long I didn't think she'd ever shut up.

"What am I suppose to do when I join? I need equations to appear correctly!"

(In the days she was interested in joining.)

Belial666 wrote:What if the whole "frame of reference" thing was an illusion of perception? Would FTL communication be possible then?



For example, you got a train car. In each end of the train car, you got a high-accuracy clock. In the middle of the train car, you got a device shooting a laser beam at each clock.
For an observer riding the train, both laser beams cross the same amount of space, hit both clocks and destroy them; the last recorded time given by both clocks is the same.
For an observer not riding the train, the train car is moving. The beam shooting towards the back of the car has less space to cross and arrives first, while the one shooting towards the front has more space to cross and arrives second. the last recorded time given by both clocks would not be the same.



However, once the train stops and the outside observer can actually see the recorded times, they happen to be identical, no matter what the outside observer saw happen.

I'm afraid that you have fallen prey to the most common mistake non-physicists make when playing with Relativity. You have not taken account of the Relativity of Simultenaity.

What actually happens is this. The observer aboard the train sees things exactly as you have described. But the moving observer sees:
At the moment the lasers fire, the clock at the rear of the train reads a different time than the clock at the front of the train! The rear clock reads a later time than the front clock.
The rear laser hits the rear clock first.
The front laser then hits the front clock.
Both broken clocks end up with the same time as observed by the observer aboard the train.

The trick about Relativity is that both perspectives are equally valid. So you are actually correct--it is an illusion of perspective. The same events will happen; it is just the timing that changes.

I'm going back to the Original Post now, and analyzing in a bit more detail the relationship between hyperspace in the Honorverse and relativity. To be clear, I am only talking about Honorverse hyperspace, which is rather different from any other hyperspace/overspace/jumpspace/higher dimension/whatever that I am aware of in fiction or scientific literature. Whenever I use the word hyperspace in this post, understand that I specifically mean Honorverse hyperspace.

One of the things we know about hyperspace is that, when you jump in or out of hyperspace, you lose 80% of your velocity. The question a physicist would ask is "80% of your velocity in what reference frame?" From the context, the answer appears to be "in the reference frame of the local star".

This leads to an inescapable conclusion: hyperspace has a preferred frame of reference. All velocities in hyperspace can be measured relative to this preferred frame of reference. I hypothesize that the preferred frame of reference is somehow locked to weighted mean frame of reference of the local stars. I might generalize that to say that it is locked to the weighted mean frame of reference of the local mass distribution in normal space.

This has very interesting consequences. The first consequence is that relativity still applies on the planetary scale, but FTL travel is still allowed because it involves a preferred frame of reference. All the usual time-travel consequences of FTL do not apply, because there is a preferred frame of reference for FTL travel.

I also hypothesize that FTL comm also uses the preferred frame of reference of hyperspace. That solves the question posed by Belial666 in the Original Post. In the Honorverse, a ship moving at relativistic speeds does not transmit FTL Comm at 62c in his own frame of reference--he transmits it at 62c in the preferred frame of reference of hyperspace. In this physics, there is no possibility of transmitting a message backwards in time.

By the way, when I said "the most common mistake non-physicists make when playing with Relativity", I did not mean playing in a demeaning way. I like to play with Relativity, too! Looking back at my post, I just realized that the phrase could be taken the wrong way. I think it's great that these questions and scenarios are coming up. There is no shame in making mistakes with Relativity--it is a really hard set of concepts to comprehend. The most common mistake, even for physicists, is to apply the concepts and equations to part of the problem, but not to some other part. (That was almost always the error on my homework when I was studying the subject.) So I'm ready to keep playing with Relativity!

The rear clock reads a later time than the front clock.

Unless you do a synchronization.

1) Shine light with a beacon at train car.
2) Train car accelerates away to acheive speed of experiment. (both clocks accelerating away from you at the same Gs since both are onboard the train)
3) When the required redshift is read, train stops accelerating (it has acheived the speed of the experiment) and the clocks start measuring.
4) Both clocks keep measuring at the same pace from your POV since both are now moving at the same speed away from you and thus get the same relativistic distortion.
5) Both clocks keep measuring at the same pace from the inside POV since both clocks are at rest towards each other.



Wouldn't that synchronize the clocks from both POVs so we could do the experiment?

Belial666 wrote:

The rear clock reads a later time than the front clock.

Unless you do a synchronization.

1) Shine light with a beacon at train car.
2) Train car accelerates away to acheive speed of experiment. (both clocks accelerating away from you at the same Gs since both are onboard the train)
3) When the required redshift is read, train stops accelerating (it has acheived the speed of the experiment) and the clocks start measuring.
4) Both clocks keep measuring at the same pace from your POV since both are now moving at the same speed away from you and thus get the same relativistic distortion.
5) Both clocks keep measuring at the same pace from the inside POV since both clocks are at rest towards each other.



Wouldn't that synchronize the clocks from both POVs so we could do the experiment?

In all relativity problems, it is standard to assume that the clocks have been synchronized in some way (there is a standard method described in physics books). But the problem is that they will only be synchronized in one frame of reference. This is because of the Relativity of Simultenaity.

If two events occur at the same place are observed in one frame of reference to be simultaneous, then every frame of reference will agree that they were simultaneous.

But if two events which are separated in space are observed in one frame of reference to be simultaneous, those events will NOT be simultaneous in any other frame of reference which is moving relative to the first frame.

Going back to your train example, you have a number of events; I'll only list a few. Let us say that the observer on the train sees the lasers hit both clocks when the clocks read 12:00. So, the rear clock strikes 12:00; call it Event A. The front clock strikes 12:00; Event B. The laser hits the rear clock; event C. The laser hits the front clock; event D.

The observer on the train sees events A, B, C, and D as simultaneous. The observer which is moving relative to the train disagrees. Events A and C are at the same place, so the second observer agrees that A and C are simultaneous--the laser hits the rear clock when the clock reads 12:00. Similarly, events B and D are at the same place, so the second observer sees the laser hit the front clock when it reads 12:00. But events A and B are not at the same location--the second observer says that clock A reads 12:00 before clock B reads 12:00.

Both observers agree that the lasers hit the clocks when the clocks read 12:00. But they disagree on whether the lasers hit simultaneously (and whether the clocks read 12:00 simultaneously).

This is probably the most non-intuitive concept in Relativity. I remember it always caused the most headaches on tests.

Sure, but where's the difference coming from? If both clocks were synchronized and both clocks are moving away from you at the same speed, wouldn't both clocks be affected (from your POV) in the same way by relativity?

Belial, you are probably wondering why your proposed method of synchronizing the clocks would not work. [edit]Heh, I see you already posted exactly that question.[/edit] The answer lies in General Relativity. Since you are accelerating the clocks, you are no longer talking about inertial frames of reference. As the train accelerates, the outside observer will see the two train clocks drifting out of synch. General Relativity is far more complicated. But one way to picture it is to remember that, as the train accelerates, it also seems to shrink as seen by the outside observer. So the Front Clock is accelerating slightly less than the center of the train, and the Rear Clock is accelerating slightly more than the center of the train. That difference in acceleration causes the clocks to drift from the perspective of the inertial frame of reference.