Basic Relativity Question

[pljames]

What is it? Where can I get some information on it? Hope I spelled it right. pljames

[Tom Mattson]

I still don't know what you're talking about. You're talking about observers in the same inertial frame, and asking if they are "relevent" to one another. I can assure you that this question has no answer in Special Relativity.

 

Now if you want to know if their assignment of spacetime coordinates to events is different, then the answer is "yes", because each is at the origin of his own coordinate system. But if you are asking if their determination of spacetime intervals between events is different, then the answer is "no".

[J.C.MacSwell]

I still don't know what you're talking about. You're talking about observers in the same inertial frame' date=' and asking if they are "relevent" to one another. I can assure you that this question has no answer in Special Relativity.

 

Now if you want to know if their assignment of spacetime [i']coordinates[/i] to events is different, then the answer is "yes", because each is at the origin of his own coordinate system. But if you are asking if their determination of spacetime intervals between events is different, then the answer is "no".

 

Do you mean at rest in the same inertial frame? (with regards to the second paragragh)

[Tom Mattson]

Do you mean at rest in the same inertial frame? (with regards to the second paragragh)

 

He specified that they are both not moving, so they have to be at rest in the same inertial frame.

[J.C.MacSwell]

He specified that they are both not moving, so they have to be at rest in the same inertial frame.

 

Thanks, I was starting to second guess myself as to what it meant to be in an inertial frame. LOL

[geistkiesel]

It isn't a paradox. Work it out for yourself: Pick a statement and try to derive both it and its negation from the postulates of SR. You won't be able to do it.

 

 

 

The measurements are different' date=' but nothing whatsoever [b']happens[/b] to the clock. The clock is not altered in any way by the fact that other bodies are in motion relative to it.

 

If observers in two inertial frames, A and B, moving relative to each other "see" each other's clocks as moving slower than their own clock then should not the application of "reciprocity" be imposed. If observers on both frames assume their motion is at rest wrt the other, then should not the clocks manifest this simple reality of SRT? I mean if both clocks are started and stopped at the same instant then the clocks should reflect the SRT reality of time dilation shouldn't they?

 

Geistkiesel

[Janus]

If observers in two inertial frames' date=' A and B, moving relative to each other "see" each other's clocks as moving slower than their own clock then should not the application of "reciprocity" be imposed. If observers on both frames assume their motion is at rest wrt the other, then should not the clocks manifest this simple reality of SRT? I mean if both clocks are started and stopped at the same instant then the clocks should reflect the SRT reality of time dilation shouldn't they?

 

Geistkiesel[/quote']

 

Relativity of Simulataneity. The clocks can only stop at the same instant according one frame, A or B. According to the other frame the clocks do not stop at the same instant.

Example: if the time dilation factor is 2, and the clocks stop at the same instant according to frame A, then from A, clock B will read 1/2 the value of clock A because clock B was running half as fast.

 

From B, clock A will run half as fast as clock B, but the two clocks do not stop at the same instant. Clock B stops, and then some time later when it finally reads twice the value of the stopped B clock, Clock A stops. Thus both frames agree as to what both clocks read when they are stopped.

[geistkiesel]

What is it? Where can I get some information on it? Hope I spelled it right. pljames

You were asking if A and B are moving relative to each other and they see athrid fra,e C, is the AC and BC inertial frame pair. A relative to C and B rel;ative to C, relative motion physically significant? Is this it?

 

I say yes. Let us assume the that C is the embankment and A and B are a train and an airplance moving uniformly with respect to the embankment.Then, if A is moving at 20 units with respect to the embankment, and B is moving 40 units with respect to the embankment, and the A and B frame are moving in the same direction, then the A and B frame may determine their intrinsic absolute velocity with respect to the embankment assumed v = 0, and they can therefore deteremine that B is moving at 20 units faster than A (or A moving 20 unuits slower than B). If A is moving 20 units above zero and B is moving 40 units above zero then B is moving 20 units faster than A. Zero velocity: here the C frame, the embankment. Also, of course, the relative motion of A with respect to B is 20 units measurable independent of the third frame. In other words there is at least two ways of doing it. here is a third:

 

 

here is a third way.

 

In any event using a common frame of reference for two or more moving objects is done every day. Such as in the Global Positioning System, GPS. Interesting dialogue regarding Special relativity and the Sagnac Effect is included in the GPS story, which does not use SRT in its calculations of position, or for coprrection purposes. GPS uses preferred frames of reference, e.g. ECEF, Earth centered earth fixed, because the preferred frames of reference work, SRT doesn't.

 

Geistkiesel

[geistkiesel]

Relativity of Simulataneity. The clocks can only stop at the same instant according one frame' date=' A or B. According to the other frame the clocks do not stop at the same instant.

Example: if the time dilation factor is 2, and the clocks stop at the same instant according to frame A, then from A, clock B will read 1/2 the value of clock A because clock B was running half as fast.

 

From B, clock A will run half as fast as clock B, but the two clocks do not stop at the same instant. Clock B stops, and then some time later when it finally reads twice the value of the stopped B clock, Clock A stops. Thus both frames agree as to what both clocks read when they are stopped.[/quote']

Janus, A and B both accelerated from earth, where A reached the uniform speed of .01c and B reached the speed .30c (both wrt earth assumed v = 0). Observrs on both frames know only the relative speed of A and B as .31c The frames are separated by a distance 1lh when, coincidentally, both begin receiving the other's continuous series of radio pusles of very short duration, spaced 1 sec apart as measured in their own frame with the time from t = 0 embedded in each pulse. The pulses continue until the frames are adjacent to each other when the radio signals cease and the clocks on each frame, print out the number of pulses sent by that ship and the number of pusles received from the other ; these numbers are sent to the other ship as the last communiatiuon of both ships, The pulses are direcrky taken from the clock timing circuits of each frame.

 

If both frame observers consider themselves at rest wrt the other, will niot one of them, at least, be surprised when the final tally of the other ship is received?

 

Geistkiesel

[geistkiesel]

Relativity of Simulataneity. The clocks can only stop at the same instant according one frame' date=' A or B. According to the other frame the clocks do not stop at the same instant.

Example: if the time dilation factor is 2, and the clocks stop at the same instant according to frame A, then from A, clock B will read 1/2 the value of clock A because clock B was running half as fast.

 

From B, clock A will run half as fast as clock B, but the two clocks do not stop at the same instant. Clock B stops, and then some time later when it finally reads twice the value of the stopped B clock, Clock A stops. Thus both frames agree as to what both clocks read when they are stopped.

[/quote']

I do not question your math, but what about each frame observer considering themselves at rest. How can thyea have any meaning when the results are as you state them with one frame having run only half the speed of the other?