Special Relativity Question

[Pyrotex]

...If I can establish a frame of reference relative to the Sun, and I can establish that ... travels relative to all other centers of galaxies (expanding from each other) is that not a universal frame of reference?

Hi Dyothelite!!

Well, actually, no.

It's a frame of reference relative to the sun, because that's where you started.

 

What you are doing is picking a geometric point where X=0, Y=0, Z=0, and where the speed and acceleration of that point are defined as zero -- and measuring EVERYTHING else "relative" to that point.

You can only define that point as being in ONE place, but you can arbitrarily pick any place you want. Once you pick the place ("the Sun") then everything is relative to that place ("the Sun").

 

Now, can you describe the motion of galaxies out to the edge of the observable universe "relative" to the Sun? YES. Does that make your reference frame "Universal"? NO. Why???

 

Einstein was using the word "universal" in the sense of: does there exist any frame of reference (FOR) that is uniquely better than any other? If so, then IT and IT ALONE can be called THE universal frame of reference. And his conclusion was, NO, there is no such best, unique, central, ideal location or point.

 

Here's an example: Ptolemy assumed the Earth made for the ideal "universal frame of reference" (UFOR). He then went on to derive math to describe the orbits of the planets. Copernicus asserted that the Sun made a "better" frame of reference; put X=0, Y=0, Z=0 at the center of the Sun and the mathematics becomes WAAAAAAAY easier. Equations describing orbits shrank by a huge amount and could be calculated in a tiny fraction of the time, and to better accuracy!

 

And then along came Johaness Kepler. He chose an abstract point for his FOR

that was the "center of mass" of the Solar System. This point was within the Sun but not at its center. The center of the Sun rotated around Kepler's FOR just as the planets did; and rotated in ellipses, not circles. Equations describing orbits shrank again and improved accuracy again.

 

So, is Kepler's FOR the "UFOR" that we seek? NO. We could choose the center of our galaxy, the center of another galaxy, the center of a galaxy cluster, and on and on. We could find any number of FOR's that were more convenient for a particular problem...

 

BUT... we can never find a "Universal" FOR that is most convenient for ALL problems.

[arkain101]

I have a question for special relativity too.

 

If there was a possibility to re-explain the dialations to describe and test SR would that be something that anyone would be interested in heavily discussing?

 

It sounds strange but I feel I have some heavy and sturdy arguments that I need hammer tested, and some members on here are great a swinging hammers!

[arkain101]

I can answer my own question here I suppose and say, that depends..

 

So why dont I go ahead and get started, right?

 

I suppose I was cautious of hearing someone saying: "arkain101, give it a rest" :) lol

[sebbysteiny]

Please excuse my ignorance, but doesn't Special Relativity suggest a geo-centric solar system? I mean after all, relative to the Earth the Sun is in motion and I am stationary.

 

Please help.

 

IN my view, it was precisely this thinking (about the limits of general frames) that got Einstein thinking that SR was not complete.

 

I think if you want a truely satifying answer to your question, you may need to study Einstein's second theory of relativity: that horrible thing called general relativity which includes a complete understanding of rotating frames.

 

I think that you can view both the sun and the Earth as being in an inertial frame. But that is only the case because it is the apparant 'force' of gravity causing the rotation. If it was an electron orbiting a proton, the electron would experience angular momentum that can only be explained if the proton and not the electron was stationary.

[Turtle]

IN my view, it was precisely this thinking (about the limits of general frames) that got Einstein thinking that SR was not complete.

 

I think if you want a truely satifying answer to your question, you may need to study Einstein's second theory of relativity: that horrible thing called general relativity which includes a complete understanding of rotating frames.

 

I question the completeness, but affirm the small neatness. When is rotation not rotation? When it is spin. :)

http://www.livescience.com/othernews/061108_strange_little.html

[sebbysteiny]

If it was an electron orbiting a proton, the electron would experience angular momentum that can only be explained if the proton and not the electron was stationary.

 

Obviously ignore the quantum mechanical complications with this example