I'd like to glean some important points out of a discussion that went bad to help people understand the unending debate between relativists and absolutists. Of course I'll only present my perspective cleaned up.
There is a very subtle distinction between a preferred frame as an absolute frame and a preferred frame as one that is agreed to by all participants. This distinction only becomes important if there were only two inhabitants floating in space with stars way in the background. An absolutist would say, they could each measure their absolute speed with a high degree of accuracy by triangulating their position to the background stars. The stars are so far away they appear to be stationary and it doesn't matter how fast they are actually moving in relation to the astronauts. A relativist would say only the relative velocity between the two matters. They could still work out what that is relative to the background stars.
Earth doesn't care what the GPS satellites' perspective of our dilated clocks is. Earth doesn't care what a muon's perspective of our clocks is.Earth wouldn't allow every space ship coming into its port to impose its time frame on Earth's. Distance markers or time beacons would be set in advance according to Earth being stationary. Earth doesn't care that a proton in the LHC sees the entire earth and LHC move around it. Relativity chooses to depict Bob as stationary and Alice moving at .6c because it's impossible to depict both as moving relative to each other at .6c in 1 STD. If you break up the depiction into 2 STD's and depict Alice as stationary and Bob as moving, you are adding the assumption that all of space is whizzing past Alice. That's impossible because space can't move past anything according to the MMX. Alice fired her engines and firing up the universe's engines so that it passes by Alice is not practical. Alice is just not sitting there like a record needle on a spinning universe because that would mean she is tethered to an arm outside the spinning universe. Let's just all agree the earth spins around the sun and not relatively vice versa.
I like relative velocity from a mathematical standpoint. I can even mathematically draw an STD where both Bob and Alice are moving through space even though it looks like Bob is depicted as stationary. I'm not an absolutist that believes in referencing all velocity relative to the CMB. But I'm practical and will choose a common reference frame to the most immovable object. That will form my background cartesian coordinates that are inescapable in relativity.
You can't claim anything is motionless. You claim you are both moving with the same relative velocity but in order to work out the math, you depict the person not initiating a change in that relative velocity at a distance from you as stationary. Or not, it doesn't matter as long as one of you starts out depicted as stationary even though neither of you are. You're confusing depiction with reality. It doesn't matter who's really moving which is what you're hung up about. An absolutist won't allow one he establishes is really moving to be depicted as stationary. Both are really moving relative to each other.
As soon as relativity starts with an STD (which is a graphical representation of Lorentz Transform equations) it needs to put down Cartesian coordinates. This is what you're saying is a preferred frame as an absolute frame and this is what relativists deny is a preferred frame but is merely an agreed to reference frame. It's no more than a piece of paper on which you can use a pencil to draw on. The drawing is not reality, it is a stick man representation that is accurate enough to make the math work.
Your point, which you just don't come out and say, is you can try to draw the same relative velocity an infinite number of ways on that graph, and you'll get an infinite different coordinate points at which Bob and Alice will end up. .6c can be drawn as Bob on earth and Alice taking off from him or Alice on earth and Bob taking off from her, or Alice and Bob both taking off in opposite directions from earth at 1/3 c and they will not end up at the same cartesian coordinates on the graph. As I said, in a depiction of true relative velocity, there is no graph, there is no background, there are just 2 participants on a pitch black starless background with no other reference than each other. That leads to no math. So relativity makes one of them the basis for the cartesian coordinates. Once that's established, they are both free to move relative to that frame even though there's no physical existence to it. This is what you call your inescapable preferred, absolute frame and what relativists call the reference frame. Potato, patatoe.
I say a reference frame is not an absolute frame. To me absolute means 1 but to you, absolute means any 1 you decide upon. This is how relativists define reference frame.
It's the same thing with your interpretation of perspective. You define it as mind power over distance like telekinesis. If I say reality is information, you define that as telegrams control reality. The sun's heat and light and gravity aren't telegrams, they're reality, that comes to us at the limit of the speed of information. Perception is the reception of that delayed information. Perception does not control the source of that information.
Again, try to understand the difference between relative and absolute. In a universe of only 2 astronauts and no stars, what kind of absolute reference could there be? Absolutely none. There could be nothing between the two they could agree upon as an absolute reference. The only thing left in this extreme example is relative motion. They're both moving but each assigns themselves as stationary and the other as moving. This is a problem for you but not a problem for relativity. Things you need to work out can be easily worked out. You decree it's a paradox, it's impossible. It is indeed a paradox but knowing that, you can work around it. Absolute motion has no paradox but since it doesn't exist (in the example I gave), who cares.
There is no such thing as "really" moving in relative motion whether it's detectable or not. Both are moving relative to each other even if they both started together and one jetted off from the other sideways. Starting together, and both assuming they're stationary, means they are both relatively stationary although you probably assume absolutely stationary. You say the guy who jetted off is accelerating and therefore in absolute motion and the other isn't, so he's "really" moving. But the stationary guy is still in relative motion even though you can prove he's not really moving. "Real" absolute motion is absolutely irrelevant.
Edited by ralfcis, 28 March 2019 - 04:20 PM.