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Some relativity question(s). I am especially interested in what Einstein would say, but there are other theories.Spaceship X is connected to spaceship Y (line ahead) by a tight elastic thread & spaceship O is nearby. X & Y & O are stationary. Do observers on X & Y & O see the thread stretch or slacken or stay the same when.....(A1) X & Y accelerate at the same rate & there is no observer on O which is stationary.(A2) X & Y accelerate at the same rate & there is an observer on O which is stationary.
(A3) X & Y accelerate at the same rate & there is an observer on O which accelerates likewise....(B3) X & Y decelerate & there is an observer on O which accelerates at the same rate in the opposite direction.
O is stationary & X & Y are going past at hi speed connected by the tight thread. Do observers on X & Y & O see the thread stretch or slacken or stay the same when.....(B1) X & Y decelerate & there is no observer on O which is stationary.(B2) X & Y decelerate & there is an observer on O which is stationary.
The situation is little different from one long ship with X being the bottom and Y being the top, with a string between them running along the interior of the ship.
Edit: This answer of mine is wrong, corrected by the one below. I am leaving it here for reference.
Ok, but i wasnt really looking for real-life effects, ie we would usually assume the string & spaceships to be massless.
I think that Einstein would say that while the relative speed tween XY & O is increasing then observer O would see that the distance tween X & Y gradually shortens (because space contracts along that line)(& anything in that space contracts accordingly)(ie string shortens, & X & Y each shorten), but, i think that heshe would say that there is no stretching or slackening of the string, it maintains its tension at all times (so u & i agree here).
Me myself (ie an aetherist)(ie a neo-Lorentzian)(ie an anti-Einsteinian),
Therefore before voicing an opinion re the fate of the string in A1 & A2 i would firstly need to know the speed & direction of the (initial) aetherwind relative to X~Y~O (when stationary),
If the acceleration resulted in a stronger apparent aetherwind felt by X & Y measured along the line of X~Y then (a) X would shorten & Y would shorten, which would result in a wider gap tween X & Y, & (b) the string would shorten, which together with the widening of the gap would mean that the string would need to stretch (& might break). But if the acceleration resulted in a weaker aetherwind then X & Y would each lengthen, the gap tween would shorten, & the string would itself lengthen, & the string would slacken.
That describes what must happen, but my original question is moreso re what do observers XYO see happen. Observer O is stationary throughout & hencely shehe will see the string stretching or slackening precisely as it happens.
Aetherists believe that an objects proper true length & size & shape is the length & size & shape that it enjoys when in the absolute reference frame (sometimes called preferred frame).
In a sense similar things can happen in the Einsteinian universe, eg if X & Y are at first getting closer, then become level with O, & then fly away, then the relative velocity relative to O will be decreasing then zero then increasing, but in all 3 cases the Einsteinian string will not change its Einsteinian tension.
All objects (spaceship)(string) shorten or lengthen equally (in any given direction)(if the aetherwind changes in that direction).
But in the aetheric universe the gap always does the opposite, when objects shrink the gap widens (in any given direction), hencely its a double whammy.
Meanwhile over in the Einsteinian universe Einsteinians cannot agree amongst themselves. Most of them say that a change in relative velocity contracts or expands the space in that direction (as seen by the stationary observer)(meaning all observers)(because all observers are stationary from their own point of view), & any object sitting or moving or accelerating in that space contracts or expands with that space. In which case the string never stretches or slackens & never breaks.
Yes my comments are likely to involve a dynamic aether, non-mainstream.
No, i dont think that it is enough, i need to know the aetherwind blowing throo the stationary observers
In the aether universe the present instant of time is universal
Good points. This is solved by assuming that observational light travels at infinite speed.
We see the same problem in Einstein's train & lightning thortX. Einstein assumes that (1) observational light travels at infinite speed (but doesn't say so) & (2) assumes that an observer can see a ray of light (this would need an assistant with a smoke machine).
Your theory has the aetherwind changing? That’s not the neo-Lorentzian view. The background aetherwind blowing at 500 kmps south to north at 20 deg off Earth's spin-axis might not change much, but the apparent wind blowing throo u & me gradually changes during each day & year due to Earth's 0.4 kmps spin & 30 kmps orbit.
For example Demjanov's 1970 MMX in Obninsk showed that the horizontal projection of the wind was 140 kmps at one time of day & had a max of 480 kmps at another time of day
QuoteIn which case the string never stretches or slackens & never breaks.If anybody says any of that, they don’t know their physics. If you want to call them Einsteinians, fine, but you seem to be talking about uneducated people.I was referring to the rezults of a poll at CERN – some said that the string doesn’t break, some said that it breaks (last i heard all of them were still getting paid).
In which case the string never stretches or slackens & never breaks.
I don’t know about that tall building stuff, my thort-X is out in space well away from mass etc.
Fast things might be contracted or might not be.
Yes, if u are stationary in the preferred or absolute reference frame then the wind is zero kmps.
QuoteIn the aether universe the present instant of time is universalSomehow I guessed that you would also adopt this divergence from Lorentz’s ideas.I don’t remember exactly what Lorentz thort (it was so long ago).
Yes i can say-assume that observational light travels at infinite speed in my string-thort-X.
In my string-thort-X i too can place my observer O within inches of the alignment of X~Y, but then the thort-X wouldn’t work proper, O needs to be well back (a very long way back), for my thort-X to make much sense. So, i need an infinite observational-light speed. That’s not a problem.
Your theory has the aetherwind changing? That’s not the neo-Lorentzian view. Comment. If u change velocity then the apparent aetherwind blowing throo u must change, the background wind can be considered constant. The background aetherwind blowing at 500 kmps south to north at 20 deg off Earth's spin-axis might not change much, but the apparent wind blowing throo u & me gradually changes during each day & year due to Earth's 0.4 kmps spin & 30 kmps orbit.
If the wind is a tailwind then a fast thing will be longer.
I am dubious re Lorentz using the word spacetime before Einstein & Co. I will have a look.
Quote from: HalcHow can something that is stationary be a tail wind? Comment. I didnt stipulate what the aethewind is or isnt, ie speed & direction, thusly it could be a tailwind or it could be a headwind. But stationary would be simpler for sure.
How can something that is stationary be a tail wind?
Not forgetting that Lorentz & Michelson & Miller & Morley & Ives & Poincare & Silberstein all died believing in aether. And Einstein died believing in aether.
Some relativity question(s). I am especially interested in what Einstein would say, but there are other theories.Spaceship X is connected to spaceship Y (line ahead) by a tight elastic thread & spaceship O is nearby. X & Y & O are stationary. Do observers on X & Y & O see the thread stretch or slacken or stay the same when.....(A1) X & Y accelerate at the same rate & there is no observer on O which is stationary.(A2) X & Y accelerate at the same rate & there is an observer on O which is stationary.(A3) X & Y accelerate at the same rate & there is an observer on O which accelerates likewise.
O is stationary & X & Y are going past at hi speed connected by the tight thread. Do observers on X & Y & O see the thread stretch or slacken or stay the same when.....(B1) X & Y decelerate & there is no observer on O which is stationary.(B2) X & Y decelerate & there is an observer on O which is stationary.(B3) X & Y decelerate & there is an observer on O which accelerates at the same rate in the opposite direction.
My Einsteinian answer is that the thread doesnt stretch or slacken or snap. But i think i noticed in wiki that the knee-jerk Einsteinian answer is that there is no change -- & wiki says that a more considered Einsteinian answer needs to account for simultaneity, in which case the thread snaps. I will have to look into that.
I dont understand how there can ever be a simultaneity~synchronization issue for X & Y in A123 & B123 (i mean assuming that they successfully synchronize at some time before)(& assuming that they do the same thing at the same time up untill the event)(& during the event). During the event they always do exactly the same thing (accelerate or decelerate) at exactly the same time. So why the problem. Am i missing something.
How can the leading ship X start its acceleration late?
Comment. No i dont see the thread snapping. Unless u mean from the g force of acceleration.
QuoteIf they resynchronise their clocks after accelerating and do so on the basis that they're now stationary, they'll end up with the leading one running behind the other (when observed by a stationary observer in the original frame). That's why the leading one will start decelerating after the trailing one, but they will see themselves as simultaneously beginning that deceleration. If they don't resynchronise their clocks though, the leading ship will not start the deceleration late, and to the people in the two ships it will appear as if the leading one starts its deceleration first. Comment. Wow, if thats the Einsteinian answer then Einsteinians are crazier than i ever thort. I dont see how X or Y can ever see the thread snap in the Einsteinian universe -- X & Y must always think themselves to be stationary relative to each other.
If they resynchronise their clocks after accelerating and do so on the basis that they're now stationary, they'll end up with the leading one running behind the other (when observed by a stationary observer in the original frame). That's why the leading one will start decelerating after the trailing one, but they will see themselves as simultaneously beginning that deceleration. If they don't resynchronise their clocks though, the leading ship will not start the deceleration late, and to the people in the two ships it will appear as if the leading one starts its deceleration first.
And i dont see how O might see the thread snap.
I get it that Einsteinian SR says that if X & Y are simultaneous in their frame then they cannot be simultaneous in any other frame (this rule is wrong)(but i can follow their logic)(albeit flawed). Thusly O will see a difference in activity of X compared to Y, but the thread doesnt snap in the XY frame, therefore the thread doesnt snap, therefore O cannot see the thread snap (still sticking to Einstein's SR rules in an Einstein universe). Anything else is batshit crazy. [/color]