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Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: syhprum on 08/03/2011 12:41:53

Title: Can anything resembling an æther be said to exist
Post by: syhprum on 08/03/2011 12:41:53
The simplistic view of an æther of a century ago is very much out of favour but the idea won't go away.
Can anything resembling an æther be said to exist
Title: Can anything resembling an æther be said to exist
Post by: yor_on on 08/03/2011 14:32:18
Einstein had those thoughts on it, addressing 'Ether and the Theory of Relativity 1920, at the University of Leyden. (http://www.tu-harburg.de/rzt/rzt/it/Ether.html)

Myself I'm of two minds. There is no aether as I know of, expressed for example as a 'resistance' in Space classically. When the Casimir effect discuss 'pressure' pulling the sphere and the plate together they are not measuring Space as having a measurable pressure or resistance, as I see it. Instead they are passing our macroscopic classical reality in that measurement, applying QM effects on classical 'empty' space.
==

What I mean there is that I think you can look at it two ways. Either as 'space' exerting a 'pressure'. Or as I, define it as no pressure at all, instead something 'missing' between the plate and sphere, creating a sort of 'negative pressure' between them. If space had a measurable pressure on objects it also should have some measurable 'resistance'. You might assume that 'resistance' to equal out in all directions of course, making it unmeasurable for us. But after all, that, to me, seems to become the same as having no 'pressure' at all.
==

And if you really want something to think about:)
Do as I and ask yourself what it is 'missing' between the sphere and the plate?

Time?
Title: Can anything resembling an æther be said to exist
Post by: JP on 08/03/2011 22:26:39
The short answer is "not unless you want to confuse people." 

Aether almost always refers to a substance permeating the universe through which light propagates in a similar way to the way in which sound propagates through matter.  This theory has been thoroughly disproven.  Of course, the universe is made up of space-time, which has properties, and is filled with fields, which have properties, but these things are physically completely different from aether.  If you resurrect the name "aether" to apply it to the properties of space-time in these these new theories, it's just overly confusing and potentially misleading, since these theories have nothing to do with what aether originally meant.  It's not a matter that the aether model just needed to be adjusted to bring it into line with the properties of space-time relativity and quantum mechanics; the aether theory has to be totally discarded and the theories of relativity and QM have to be renamed as aether in order to make the claim that it still exists.   

Of course, that's what Einstein is getting at in the lecture that Yor_on linked: that space-time has properties just like aether used to, so you could call it akin to aether.  But this lecture also gets used a lot to promote fringe theories, which kind of makes the point that it's a very confusing analogy to make.  That's probably why you don't really find it used in modern textbooks. 
Title: Can anything resembling an æther be said to exist
Post by: Geezer on 09/03/2011 01:07:32
Aether to a JP is like centrifugal force to a Geezer.  [;D]
Title: Can anything resembling an æther be said to exist
Post by: syhprum on 09/03/2011 10:35:33
I will remove ALT 145 from my list of useful key strokes
Title: Can anything resembling an æther be said to exist
Post by: Ron Hughes on 09/03/2011 17:57:42
Can we see anything in the Universe that might suggest an either? One possibility is the existence of spiral galaxies. If all the matter in a spiral galaxy has had the same rotation speed since their formation why wouldn't all the arms just be sticking straight out from the center instead of bending back away from the direction of rotation? It looks as if some very very small force is dragging on them as they rotate.
Title: Can anything resembling an æther be said to exist
Post by: JP on 09/03/2011 18:24:36
But what laws of physics say that all the matter should have the same rotation speed?  The fact that the orbital velocity does seem pretty constant as you move away from the center is a big question--and a major reason for postulating dark matter: http://en.wikipedia.org/wiki/Galaxy_rotation_curve  Extra gravity from the dark matter explains the observations quite well, apparently. 

But even if you want to postulate something else to explain this issue, it still shouldn't be called aether, because that brings up the idea that it's a material medium for light propagation, which it isn't!  Again, it's taking an old word that means something completely different to explain something that may exist in space.
Title: Can anything resembling an æther be said to exist
Post by: syhprum on 09/03/2011 19:59:02
Using the æ***r word has made me feel like the American who has let slip the n****r word or the "actress" who mentioned her c**t on TV
Title: Can anything resembling an æther be said to exist
Post by: JP on 09/03/2011 20:52:19
Ooh!  I like that.  Maybe we can add it to the forum blacklist!

And throw in c*********l as well, for Geezer!
Title: Can anything resembling an æther be said to exist
Post by: Ron Hughes on 09/03/2011 22:08:51
jp, it doesn't imply the either is a material thing only that there is a possibility that space is something like a very weak electrical field that was very strong at the time T = 0. If this where true it would explain why the vacuum permeability has it's current value and would suggest that value would have been very large at the beginning. Is it possible that c could be linked to the permeability of space or it's value might have been a million times greater at the beginning explaining the need for inflation?
Title: Can anything resembling an æther be said to exist
Post by: JP on 09/03/2011 22:28:18
Ron, I'm sticking by my guns that the term aether is too misleading to use for anything other than it's original intent: that of a substance through which light propagates, precluding the vacuum, since space itself isn't really a substance in the sense the aether theory intended.  Of course the universe has properties and if fundamental constants vary in time, this could lead to interesting results, but I don't see why we need to bring a confusing term like aether into it.  Why not just say that the constants might vary with time?
Title: Can anything resembling an æther be said to exist
Post by: Ron Hughes on 10/03/2011 00:16:58
jp I won't argue with that but the fact remains that something causes spiral galaxies and the invention of dark matter and dark energy ( two things that experiment can never prove ) to explain observation seems to me like a drowning man grasping for straws. We have permeability suggesting that there is something to space related to how fields interact and I like the idea of an electric field explaining permeability.
Title: Can anything resembling an æther be said to exist
Post by: JP on 10/03/2011 03:07:14
I won't argue dark matter/energy with you here, though I disagree with your views.  I think this thread was mostly about whether the word "aether" is appropriate to apply to properties of space-time, and my point was that it isn't!
Title: Can anything resembling an æther be said to exist
Post by: Ron Hughes on 10/03/2011 05:53:03
See,   http://en.wikipedia.org/wiki/Aether_%28classical_element%29

The OP ashes, is there something that could be called an aether. I answer yes, a very weak electric field.
Title: Can anything resembling an æther be said to exist
Post by: Geezer on 10/03/2011 05:55:47
And throw in c*********l as well, for Geezer!

Why would you want to blacklist ceremonial?
Title: Can anything resembling an æther be said to exist
Post by: Ron Hughes on 10/03/2011 16:28:00
BTW yor-on, tell if I'm wrong. Quantum field theory's explanation of the Casimir effect is based entirely on the assumption that no fields exist between the plates.
Title: Can anything resembling an æther be said to exist
Post by: yor_on on 10/03/2011 19:16:38
Depends on how you think of it I guess. Do 'time' come in clumps? Like certain amounts fitted to macroscopically defined 'systems', and other defined for QM? Or is our 'times arrow' valid everywhere? After all, it's that 'arrow' we make our observations through and in? I've seen it explained as 'virtual wavelengths', some 'fitting' between the sphere and the plate, some 'too big'.

Lightarrow gave a alternative explanation ala Feynman in where the 'intrinsic'(?) interference of those 'virtual waves' becomes the main reason for why the 'attraction' develops, making some waves more 'probable' than others. What one can notice is that this explanation seems to make no difference between 'ordinary measurable radiation' and 'virtual radiation'? To me though it seems to have to do with the arrow somehow? Consider the expansion, you can explain it looking at three dimensions crisscrossing, creating new 'distance' but then you have to ask yourself what 'comes up first', that those 'dimensions knit up' into a distance. Or you can see it as 'geometries' expanding in 'time' no crisscrossing needed as every point in space is a whole finished 3D geometry when it gets introduced into our 'reality'. I find the later simpler to imagine myself, not that any of them makes sense :)