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superluminal
07-27-05, 04:44 AM
PLEASE PLEASE!!! This is for discussion of standard SRT only! Feel free to copy this OP to another thread to speculate on the validity of SRT! THANKS!

So my web page seems to be down. The link below will open the animation attachment.

SRT1 (http://www.sciforums.com/attachment.php?attachmentid=4225&stc=1
)
or
http://www.laserwireless.net/Diagrams/metrics.gif

Interesting animation huh? This is based purely on the basic postulates of SRT and the Lorentz transforms in an attempt to clarify some recent discussions.

Ok. A and B start 1ly apart with their clocks synchronized by a midpoint signal. Plate 0 is just prior to the start of A's trip toward B. (I will use plate N to refer to the frames of the animation - upper left corner - since frame could be very confusing).

Plate 1 is the instant just after A starts toward B. I allow the ships to accelerate and decelerate instantaneously.

Now, there has been some confusion over what explains the "twin paradox". In my animation (a one way version), A arrives at B half a year younger than B. The "acceleration phase" is a popular "explanation" but has nothing to do with it and explains nothing. Change in velocity is all that counts.

When two objects, A and B share the same frame, what does this mean? It means that the space and time metrics for each are the same. They agree on distances and durations. When one of them begins to move, he is now in a different frame. The metrics for distance and time that A and B formerly agreed upon now no longer match. Do the spacetime metrics change for B who did nothing? Nope. B still sees A 1ly away (magic telescope). B will see A contracted in length and time since there is now relative motion. Just as A will see B length and time contracted.

A note. The postulate regarding preferred frames (there are none) does not imply symmetry outside of that frame. It simply means that you in your frame are at rest and Newtonian physics rules.

In the top diagram you see the distance between A and B contract. Why does B not see the same thing? Simple. A changed his state of motion through spacetime while B did not, thus redefining the metrics A used to measure distances. Spacetime is a real thing, not just a mathematical construct. We move through it. And when we change our motion through it, our metric for space and time measurements outside our frame, changes.

When A reaches B in the top diagram and instantly decelerates, A again shares the exact spacetime metrics that B does. If the deceleration was not instantaneous, A would see B’s clock racing forward at an increasing rate as the deceleration continued, until it reached 1.150.

Hopefully this helps with the atmospheric muon discussions also.

Let's tear into it! Big fun!

geistkiesel
07-27-05, 05:29 AM
PLEASE PLEASE!!! This is for discussion of standard SRT only! Feel free to copy this OP to another thread to speculate on the validity of SRT! THANKS!

So my web page seems to be down. The link below will open the animation attachment.

SRT1 (http://www.sciforums.com/attachment.php?attachmentid=4225&stc=1
)

The times are the same numbers, but B arrives at A before A arrives at B.
BTW the link is a simulation, not a real experiment. And, B jumps ahead half the distance i.e. B gets a head start on A , no wonder B wins the race. I know, switch the labels A->B, B->A and all is well; well well well, science marches on. Yes, yes, all is relative isn't it?

Geistkiesel:cool

funkstar
07-27-05, 06:06 AM
Good post, superluminal.

2inquisitive
07-27-05, 06:07 AM
by superluminal:

When one of them begins to move, he is now in a different frame. The metrics for distance and time that A and B formerly agreed upon now no longer match. Do the spacetime metrics change for B who did nothing?
================================================== =============

How do you determine which of two observers, alone in the universe, begins to move?
That is the basis for STR, you cannot know which is moving, or if both are moving
using only those two observers and nothing else. An acceleration, a non-inertial frame,
is the only way to determine which began to move.

superluminal
07-27-05, 06:19 AM
2inq,

How do you determine which of two observers, alone in the universe, begins to move?

That is the basis for STR, you cannot know which is moving, or if both are moving using only those two observers and nothing else. An acceleration, a non-inertial frame,is the only way to determine which began to move.

And A did just that. I stated that I am allowing instantaneous accelerations since it dosen't matter. A fired his instant accelerator rockets (?) while B did nothing.

superluminal
07-27-05, 06:19 AM
funkstar,

Thx.

2inquisitive
07-28-05, 05:10 PM
2inq,



And A did just that. I stated that I am allowing instantaneous accelerations since it dosen't matter. A fired his instant accelerator rockets (?) while B did nothing.

"The "acceleration phase" is a popular "explanation" but has nothing to do with it and explains nothing. Change in velocity is all that counts."

I misunderstood you to mean an acceleration phase (non-inertial frame) was
not necessary to explain the twin paradox. I now understand what you are saying and agree with you, superluminal.