Special Relativity Question

[Dyothelite]

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.

[Turtle]

Curious where you came to that speculation? :D The Earth orbits the Sun, not the other way. We live in a heliocentric solar system. :phones:

[Dyothelite]

Well obviously because we can determione a pluralistic system based on the other planets, but doesn't special relativity say that that is essentially an illusion because we cannot truly formulate fixed frames of reference and that it is equally valid to say relative to the Earth all things are moving relative to me.

[Turtle]

Well obviously because we can determione a pluralistic system based on the other planets, but doesn't special relativity say that that is essentially an illusion because we cannot truly formulate fixed frames of reference and that it is equally valid to say relative to the Earth all things are moving relative to me.

 

No, special relativity does not say that. In the words 'geocentric' and 'heliocentric', the suffix -centric refers to the geometric axis (or center) of revolution. It is a specific mathematically rigorous terminology and no amount of verbal gymnastics changes that.

[Buffy]

In simplest terms, SR says the appearance of everything can only be measured by defining a frame of reference. There is no "right"--or more formally "absolute"--frame of reference. We all see the same things differently because we have different points of view.

 

This really has nothing to do with heliocentrism though, which was simply the realization that although its possible to model the motion of the planets using "epicycles" they actually move in ellipsoid orbits. This is an observable fact, and has nothing to do with "appearances" in SR, where the *real* measurements of different observers are different. In the case of the Ptolemaic system, if we could have measured distances to planets accurately, it would have been obvious that the motions did not obey Ptolemy's model...

 

With a joyful shout, :phones:

Buffy

[Dyothelite]

This is all cool with me, I'm not argueing for a geo-centric worldview, I'm just concerned that SR suggests you cannot form universal frames of reference or even local frames of reference. If its all good to say that the Sun is essentially stationary and the planets are orbiting it and SR won't pop up and refute it, I'll be equally content.

 

Again, I'm a novice. I'm not trying to suggest otherwise. I'm sorry if I seem like I'm trying to sound smart. I'm simply a student.

[Buffy]

I'm just concerned that SR suggests you cannot form universal frames of reference or even local frames of reference.

Universal reference frames: sorry Charlie, nope. Local reference frames: no problem, but with enough distance, even in local reference frames two observers can see different things! :phones:

If its all good to say that the Sun is essentially stationary and the planets are orbiting it and SR won't pop up and refute it, I'll be equally content.

Does. But only from your own reference frame....

Again, I'm a novice. I'm not trying to suggest otherwise. I'm sorry if I seem like I'm trying to sound smart. I'm simply a student.

Not a problem! How else would one learn?

 

The question not asked,

Buffy

[Turtle]

This is all cool with me, I'm not argueing for a geo-centric worldview, I'm just concerned that SR suggests you cannot form universal frames of reference or even local frames of reference. If its all good to say that the Sun is essentially stationary and the planets are orbiting it and SR won't pop up and refute it, I'll be equally content.

 

Again, I'm a novice. I'm not trying to suggest otherwise. I'm sorry if I seem like I'm trying to sound smart. I'm simply a student.

 

We're simply teachers. :phones: I have bolded part of your reply for clarification. The Sun, while the center of the revolutionary axes of the Earth and planets, is not stationary. The Sun rotates on its axis, and at the same time revolves around our galaxy's center (the Milky Way). The Sun's rotation rate on its axis is about once every 25 days, and its rate of revolution around the galactic center is once every 100,000 years.

[Dyothelite]

One last thing:

 

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

[Turtle]

One last thing:

 

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

 

The relative 'travel' among galaxies is not the revolutionary travel I previously described. Inasmuch as we live in the universe, and the prefix uni- means 'one', then it is redundant and/or circular to say it's a 'universal frame of reference'.

[Buffy]

To echo Turtle here: you only get one frame of reference at a time!

 

Whereever you go, there you are, and what you see from there is all you can see! Go someplace else and it will look totally different!

 

There is no center, how radical,

Buffy

[Dyothelite]

How then can we say there was a Big Bang based on observation of the red-shifts of galaxies? If there is no constant between the galaxies then isn't the statement that they all expanded from a certain point invalid?

[Buffy]

How then can we say there was a Big Bang based on observation of the red-shifts of galaxies? If there is no constant between the galaxies then isn't the statement that they all expanded from a certain point invalid?

Yep. No "central point" everything is moving away from everything else *no matter where you are*!!!

 

If there was a center, you'd be able to see one side of the universe receding faster than the other side, *unless* we just happened to be exactly at the center of the universe (which actually can be proven not to be the case, simply due to the parallax opportunity for observation from the diameter of the Earth's orbit).

 

The universe is "Isomorphic" as we say in cosmology: the same everywhere for all observers.

 

The real explanation is that its best to think of our universe not expanding into space but into time, which can be really hard to grok.

 

Looking Backward,

Buffy

[Southtown]

Then would everything be positionally stagnant? (relatively =P)

[Turtle]

Then would everything be positionally stagnant? (relatively =P)

 

Yes, just like snowflakes. :phones:

[Qfwfq]

I mean after all, relative to the Earth the Sun is in motion and I am stationary.

This is perfectly correct, but SR distinguishes between inertial and non-inertial frames of reference. One that's based on Earth's position is less inertial than one that's based on the sun's. One that's rotating with Earth is even less inertial than one that considers the fixed stars as being in constant directions (neglecting parallax), according to this one the sun is circling us every year instead of every solar day.

 

This, according to special relativity. General relativity is a somewhat different kettle of fish.

[cwes99_03]

Basically, you've been given the run around it seems.

 

Yes, relativity does say that there is no one single reference from which all things should be described. As Qfwfq pointed out there are inertial and non-inertial reference frames.

 

Your thought process isn't completely invalid as some have suggested. However, what you must realize is that based on your choice of reference frame (which should be taught in a physics 101 course) you will need to use different equations and trig to solve. Thus using earth as your reference frame does not make the science invalid, but it makes your choice of equations different. You can't use an x,y,z (euclidian?) equation on a spherical reference frame.

 

Likewise, we have come to the realization that the best equations (Kepplerian?) for cosmic motion are centered upon the largest mass body in the system. If you want, you can describe the system based on a reference frame elsewhere, but why make the work harder for yourself.

 

So a short answer, yes. Relativity does allow for a geocentric view of motion, but it does not say that everything (actually) revolves around that frame of reference. If you want to say however that you can view the motion of the planets as geocentric, that's fine, but realize that you have loads more work for yourself in describing it (retrograde motion equations each being different for each planet, etc. etc. etc.).