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But you agree that no force is applied. So how do you change the speed of either object without applying the force of acceleration? Maybe you hadn't thought that through. I suggest that you do.
Me: "Same question in reverse: Do you think that Earth changes shape as a result of how it is observed?" You: "No....I can't see any sign of even an imagined contradiction there.”Like... Earth changes shape with no force applied. That is a clear sign of contradiction. So is the imaginary acceleration of Earth to near 'c' and then claiming that no force is applied.
I am losing patience again with this conversation.
"Stuff" exists and moves through space and there is space between such things.What in that requires "enforcement?" Light naturally travels at constant 'c' through space without something "restricting" it to this finite velocity.
Minkowski invented "the fabric of spacetime," and then Einstein endorsed it and built the GR theory of gravity around mass curving "spacetime."(It remains merely an abstract concept describing a coordinate system incorporating 3-D space and time to account for movement.
The problem is that physics abhors ontology, so nobody ever address the questions, "What is space?" (besides the obvious 3-D volume), "What is time" (besides the concept of 'that which elapses' as things move in space), and "What is spacetime?" (the coalescence of the two "non-entities" as examined in a paper by Brown and Pooley, "Minkowski's spactime; a glorious non-entity.")
Old guy, is this you asking on another forum and receiving the same answer back in February? mikhttp://www.physforum.com/index.php?showtopic=38507
I imagine space as volume with three axes/dimensions. Distance is the linear component of this volume. There are (grammar edit) about 93 million miles of distance (space) between Earth and Sun.
It varies a bit with Earth's position in its elliptical orbit but not with differences in how that distance is observed by varying frames of reference.
Quote from: old guy on 25/09/2012 21:43:41I imagine space as volume with three axes/dimensions. Distance is the linear component of this volume. There are (grammar edit) about 93 million miles of distance (space) between Earth and Sun.QuoteSo how do things know where they are relative to other things to work out whether to bump into them or not? Do they all keep a record of their coordinates and keep asking all the other objects to tell them theirs so that they can work out what or whether to do anything with them? That works in a computer simulation, but it's a much more complicated way of doing things than having an actual fabric of space imposing location directly on the things travelling through it.Huh? Do you need basic astronomy lessons and don't know that gravity works to hold the planets in their elliptical orbits around the Sun? Earth orbits the Sun just fine without a man-made coordinate system to follow for instructions!QuoteIt varies a bit with Earth's position in its elliptical orbit but not with differences in how that distance is observed by varying frames of reference.QuoteThat means it's a broken model then as it can't handle the result of MM.Really?! Do you really not understand that as Earth orbits the Sun it is closer at some points and further away at other points in the elliptical path?Do you think that our measurements change any of that? By what force might the Earth *actually* be moved to, say, 15 million miles from the Sun, if it were so measured from the familiar relativistic fly-by frame? How would Earth then avoid being incinerated?
So how do things know where they are relative to other things to work out whether to bump into them or not? Do they all keep a record of their coordinates and keep asking all the other objects to tell them theirs so that they can work out what or whether to do anything with them? That works in a computer simulation, but it's a much more complicated way of doing things than having an actual fabric of space imposing location directly on the things travelling through it.
That means it's a broken model then as it can't handle the result of MM.
Huh? Do you need basic astronomy lessons and don't know that gravity works to hold the planets in their elliptical orbits around the Sun? Earth orbits the Sun just fine without a man-made coordinate system to follow for instructions!
QuoteQuoteIt varies a bit with Earth's position in its elliptical orbit but not with differences in how that distance is observed by varying frames of reference.That means it's a broken model then as it can't handle the result of MM.Really?! Do you really not understand that as Earth orbits the Sun it is closer at some points and further away at other points in the elliptical path?
QuoteIt varies a bit with Earth's position in its elliptical orbit but not with differences in how that distance is observed by varying frames of reference.That means it's a broken model then as it can't handle the result of MM.
Do you think that our measurements change any of that? By what force might the Earth *actually* be moved to, say, 15 million miles from the Sun, if it were so measured from the familiar relativistic fly-by frame? How would Earth then avoid being incinerated?
So you don't have everything storing its position as coordinates, and you don't have a fabric of space either, but you do have a volume of space which serves exactly the same role as a fabric of space by enforcing distances. My point was that your volume of space is not mere nothing - it must be a fabric of space if it is to perform the role that you have it performing.
Really?! Do you really not understand that as Earth orbits the Sun it is closer at some points and further away at other points in the elliptical path?Do you think that our measurements change any of that? By what force might the Earth *actually* be moved to, say, 15 million miles from the Sun, if it were so measured from the familiar relativistic fly-by frame? How would Earth then avoid being incinerated?
Our measurements don't change the physical arrangement of anything - merely their apparent arrangement. The idea that observing things from different frames physically changes the thing being observed is exclusive to an extremist group within SR and you are wasting your time attacking it - it is not mainstream anything.
In a Lorentzian universe though, the Earth could really be much closer to the sun during parts of its orbit than we think it is (dependent on the sun and our galaxy moving at ridiculously but not impossibly high speed through space), but the heat reaching the Earth from the sun would be no different from normal due to the concentration of heat and light forwards in the direction of travel and the extra distance through space it would have to cover to reach the Earth if the Earth is moving ahead of it.
"Enforcing" is a very strange concept in this context, with absolutely no relevance to the fact that planets orbit the Sun according to the law of gravity, which requires no (metaphorical) "fabric" as an analytical coordinate system.
You are clearly not familiar with the many scholarly papers over the years presented at the conferences held by the International Society for the Advanced Study of Spacetime.
You beat on that drum assuming that space, time, and "the fabric of spacetime" exist as entities. Three dimensional volume (space) contains entities, including objects and forces. Space itself is the volume in which entities exist, not itself an entity. Planets are such objects and the gravity which holds them in orbit around the Sun is a force.
If you review this thread you will find that what passes for mainstream SR in this forum holds exactly the position you call extremist. Don't worry about how I spend my time, wasted or not. I have objected to this mainstream position on length contraction for many years, and my participation here is still focused on correcting the misconception that reality (as in the physical examples I use) changes as measurements of things/distances change as observed from different frames of reference.
A detail I didn't mention in yesterday's reply:Everything you said after "In a Lorentzian universe..." was gibberish.
"We think it is", as precisely measured from Earth at all points in its orbit, on average about 93 miles from Earth. If Earth were closer, it would be hotter. At 15 million miles away (the theoretically length contracted extreme) it would in fact be incinerated.
None of that has anything to do with "...(dependent on the sun and our galaxy moving at ridiculously but not impossibly high speed through space)"...Velocity makes no sense without specifying "relative to what?", and Earth-Sun are in the same frame relative to how our galaxy is moving through space relative to other galaxies and cosmic expansion in general.
So the challenge here in my example is, in the frame of Earth and Sun, how far is Earth from Sun, and does that distance change as a result of theoretical relativistic, fly-by measurements, not in the at rest frame with Earth-Sun. The answer is no. Length contraction as applied to the AU is... well... bogus!
In no theory does the real distance change just by moving past the solar system at high speed, but in SR there will be shorter pathways opened up by that fast movement which make the distance between the Earth and Sun appear to be less if they're aren't lined up at 90 degrees to the direction of travel of the fast-moving observer. The shortened distance for that fast-moving observer is absolutely real, but he has not actually moved the Earth nearer to the sun.
I said, answering your direct question, that I "imagine" space to be the 3-D volume in which objects move around, guided by the force of gravity. I also said that distance is the linear component of that 3-D volume. (Do you even know what that means?) So, as solar systems form around stars, planets are formed as nearly spherical (not flattened) and the distances between them are due to where/how the raw materials of each body were distributed as the planets were formed and distributed in space.
You completely distort what I say, either intentionally or because of total failure to understand what I said in the first place*. Since attribute no malice to you (only extreme arrogance and obsession with your own agenda), I will go with the latter.*
Finishing my reply to D.C. yesterday... and hopefully finishing my conversation with him, though that hope will, no doubt, be in vain!
Re: "In no theory does the real distance change just by moving past the solar system at high speed..."That is factually incorrect. Mainstream length contraction theory is based on relativity's dictum that all frames of reference are equally valid, so that when a frame measures an object or distance to be contracted, it IS contracted, not just APPEARS TO BE contracted.
The phrase which is always attached as a qualifier is some form of "for observer A"... the object/distance is contracted, while "for observer B" it is quite different in length/shape/distance. The "all frames equally valid" dictum says that a 15 million mile AU (measured from the relativistic speed frame) is equally valid with the standard 93 million mile or so average AU. I have argued that point many times with relativity theorists over the years. Your "in no theory..." statement is false.
Your statement:..."but in SR there will be shorter pathways opened up by that fast movement which make the distance between the Earth and Sun appear to be less..."Then you say, "The shortened distance for that fast-moving observer is absolutely real, but he has not actually moved the Earth nearer to the sun."Another contradiction: Does faster movement create a shorter pathway (distance) or is does it just "appear to be less...?" How can a "shortened distance" be "absolutely real" and yet the distance between Earth and Sun has not changed? You are very confused.
Introducing the phrase "for that fast-moving observer" does not change the Reality of the distance between Earth and Sun. Is that so difficult to understand? This difference, again, is the main issue of my length contraction threads, a difference clearly still lost on you. "For" the fast moving frame the distance traveled/measured may *appear* shorter. That appearance does not make Earth and Sun closer than 93 million miles apart. You still don't get it, and I give up on explaining the difference to you.
You didn't even get the difference between the *real/actual length* of the "alien probe" (20 meters) and its *apparent (contracted) length*(10 meters.) That difference was why the probe would not fit into the 10 meter cargo bay sent out to capture it. You danced all around that one and still didn't get it. That was a "reality check" on how "real" length contraction is. (Not real; only apparent.)
Quote from: simplified on 13/09/2012 16:06:05Someone on the bus should send his photons at 150 degrees relatively of own motion direction.Yes - that's what I meant by 60 degrees behind, but you've expressed it better.
Someone on the bus should send his photons at 150 degrees relatively of own motion direction.
Quote from: David Cooper on 13/09/2012 21:21:39Quote from: simplified on 13/09/2012 16:06:05Someone on the bus should send his photons at 150 degrees relatively of own motion direction.Yes - that's what I meant by 60 degrees behind, but you've expressed it better.And if I am motionless observer then the light(of instant flash) travels by way of one arch of wave(if to not calculate energy waves) relatively of me.Therefore I can see the light under the same mirror angle.
I apologise if anything I've said has been taken as a personal attack. When I describe a question as stupid, it doesn't mean the person who asked it is stupid. We are all capable of asking stupid questions, and I recently asked one here about things being in more than one place at a time (where my way of testing the properties of such a thing would actually have destroyed its ability to be in more than one place at a time). I don't take any of Old Guy's comments as a personal attacks on me either - he is merely expressing frustration with this situation as things don't appear to be getting anywhere, but it is that that makes this particularly interesting as we continue to try to identify a key point where something might be forced to give.
David,While I appreciate that you don't mean offense or take offense from the comments in this thread, my request to refrain from personal attacks also has to do with keeping the tone of the forum mild enough that other users can't take offense at it. If it were acceptable here to label questions stupid or to call other users arrogant, then we'd end up dissuading a lot of users from posting here, even if no offense was meant.So regardless of what your intent is, please keep this in mind in future posts.Thanks!
** You beat on that drum assuming that space, time, and "the fabric of spacetime" exist as entities. Three dimensional volume (space) contains entities, including objects and forces. Space itself is the volume in which entities exist, not itself an entity. Planets are such objects and the gravity which holds them in orbit around the Sun is a force.**
It doesn't work without a fabric. Your volume is a fabric, regardless of your inability to recognise a fabric of more than two dimensions. If your volume was literally nothing, it would not be able to dictate separations between things - two things with literally nothing between them must be touching.......What you need to do then is up your game so that you can speak out of knowledge instead of ignorance,
And that isn't a fabric of space? What's the difference between the two ideas then? Your 3D volume isn't just nothing - it enforces three space dimensions on its contents rather than four or five of them. You have distances enforced by your 3D volume too, so how is there no fabric of space in this? When light travels through your 3D volume, how is it restricted to the speed of light? What is it interacting with that enables it to maintain exactly the right speed while it travels through your 3D volume for billions of years?