Question about Ether and Space-Time. What's the difference?

Isn't Space/Time just a modern version of the Aether?
Any serious replies will be appreciated. Thanks.


SA

"Spacealien01" wrote in message
...
Isn't Space/Time just a modern version of the Aether?
Any serious replies will be appreciated. Thanks.


The idea of Aether and the idea of space-time certainly do have a lot in
common. Both ideas say that empty space isn't nothing, but actually
something, on some level.
The idea that spacecraft would have to propel themselves through the aether
in roughly the same manner as ships through water does seem silly to us now.
However, the current ideas of "warp drive" come pretty close, in that they
propose that by compressing space-time in front of the craft, and letting it
expand behind the craft, would make it possible to effectively travel faster
than light. That would be motion through direct influence on the "medium"
that the craft moves through - creating a space-time wave, and then surfing
that wave. Pretty outlandish stuff, but possible in theory. The biggest
problem is, of course, where to get the stupendous amount of energy that
would be needed.

Though the idea of space-time and that of aether have a lot in common,
space-time theory does predict things that the old aether theory didn't.
Perhaps it is fair to say they are related, but importantly space-time has a
proper mathematical foundation which can be used to predict things. Aether
was thought to be a mystical liquid substance - something for alchemists to
deal with according to esoteric magical rules.
Perhaps it was the intuitive precursor to the fully formed theory we have
today?

Spacealien01 wrote in message
...
Isn't Space/Time just a modern version of the Aether?
Any serious replies will be appreciated. Thanks.

"According to the general theory of relativity space is endowed with
physical qualities; in this sense, therefore, there exists an aether.
According to the general theory of relativity space without aether is
unthinkable."

A. Einstein, "Sidelights on Relativity," Dover Publications, Inc., 1922,
page 23.

--
greywolf42
ubi dubium ibi libertas
{remove planet for return e-mail}

greywolf42 wrote:

"According to the general theory of relativity space is endowed with
physical qualities; in this sense, therefore, there exists an aether.
According to the general theory of relativity space without aether is
unthinkable."

A. Einstein, "Sidelights on Relativity," Dover Publications, Inc., 1922,
page 23.

The remainder of the quote:

"Recapitulating, we may say that according to the general theory
of relativity space is endowed with physical qualities; in this sense,
therefore, there exists an ether.

According to the general theory of relativity space without ether
is unthinkable; for in such space there not only would be no
propagation of light, but also no possibility of existence for
standards of space and time (measuring-rods and clocks), nor
therefore any space-time intervals in the physical sense. But
this ether may not be thought of as endowed with the quality
characteristic of ponderable media, as consisting of parts which
may be tracked through time.

The idea of motion may not be applied to it."

Steve Carlip

wrote in message ...
greywolf42 wrote:

"According to the general theory of relativity space is endowed with
physical qualities; in this sense, therefore, there exists an aether.
According to the general theory of relativity space without aether is
unthinkable."

A. Einstein, "Sidelights on Relativity," Dover Publications, Inc., 1922,
page 23.

The remainder of the quote:

"Recapitulating, we may say that according to the general theory
of relativity space is endowed with physical qualities; in this sense,
therefore, there exists an ether.

According to the general theory of relativity space without ether
is unthinkable; for in such space there not only would be no
propagation of light, but also no possibility of existence for
standards of space and time (measuring-rods and clocks), nor
therefore any space-time intervals in the physical sense. But
this ether may not be thought of as endowed with the quality
characteristic of ponderable media, as consisting of parts which
may be tracked through time.

The idea of motion may not be applied to it."

OK, let's look at the saliant point to this paragraph.

- According to the general theory of relativity space
without ether is unthinkable...

Why did Einstein think this?

- for in such space there not only would be no propagation
of light

{why, if light can indeed travel in vacuu}

- but also no possibility of existence for standards of
space and time (measuring-rods and clocks)

{again, why?}

- nor therefore any space-time intervals in the physical
sense

{Certainly there can be space & time intevals in purely conceptual
abstraction, what does he mean by 'physical sense'?}

- But this ether may not be thought of as endowed with the
quality characteristic of ponderable media...

{This seems to be saying that the aether isn't ponderable matter
yup, that makes sense...}

- as consisting of parts which may be tracked through time.
The idea of motion may not be applied to it...

And we come at last to what appears to be your point, namely that the
individual constituent elements or particles cannot be trackd. Well
Steve, can we track the individual molecules in a cubic centimeter of
air through time? Or, do we instead treat the aglomomration of these
statistically, as a continuum process? If all one has is elements made
up of the very same medium the stress/strain deformations guarantee that
one cannot directly detect motion relative to the underlying medium.

But it is very clear in this passage that Einstein is saying that the
ether (a.k.a. an underlying physical medium) is very real...

Paul Stowe

Paul Stowe wrote:
[...]
OK, let's look at the saliant point to this paragraph.

- According to the general theory of relativity space
without ether is unthinkable...
[...]

- But this ether may not be thought of as endowed with the
quality characteristic of ponderable media...

{This seems to be saying that the aether isn't ponderable matter
yup, that makes sense...}

- as consisting of parts which may be tracked through time.
The idea of motion may not be applied to it...

And we come at last to what appears to be your point, namely that the
individual constituent elements or particles cannot be trackd. Well
Steve, can we track the individual molecules in a cubic centimeter of
air through time? Or, do we instead treat the aglomomration of these
statistically, as a continuum process? If all one has is elements made
up of the very same medium the stress/strain deformations guarantee that
one cannot directly detect motion relative to the underlying medium.

That's not what Einstein said at all. You can find the full text,
thanks to Project Gutenberg, at
http://www.gutenberg.net/etext05/slrtv10.txt

Another quote from the same essay:

"We may assume the existence of an ether; only we must give up
ascribing a definite state of motion to it, i.e. we must by abstraction
take from it the last mechanical characteristic which Lorentz had
still left it."

Steve Carlip

wrote:

That's not what Einstein said at all. You can find the full text,
thanks to Project Gutenberg, at
http://www.gutenberg.net/etext05/slrtv10.txt


The full quote: "There are weighty arguements to be adduced in favor of
the aether hypothesis. To deny Aether is ultimately to assume that
that physical space has no physical qualities whatever. The fundamental
facts or mechanics do not harmonize with this view...according
to the general theory of relativity space is endowed with physical
qualities; in this sense, therefore, there exists an aether. According
to the General Theory of Relativity space without aether is unthinkable."

Another quote from the same essay:

"We may assume the existence of an ether; only we must give up
ascribing a definite state of motion to it, i.e. we must by abstraction
take from it the last mechanical characteristic which Lorentz had
still left it."

He is talking here about "aether drift". That does not imply that
there are no "mechanical" properties. Either that or Einstein isn't
being very consistent.

Today the aether model has simply been thrown out and replaced
with pure mathematics. Lame excuses, like things being "unknowable"
abound. Let's see. Einstein thought quantum mechanics was bunk
and aether essential! Gosh, I may be a kook, but I seem to be
in some pretty good company!

bjacoby
(Just call me Min jr.)
--
Due to SPAM innundation above address is turned off!

wrote:
wrote:

Another quote from the same essay:

"We may assume the existence of an ether; only we must give up
ascribing a definite state of motion to it, i.e. we must by abstraction
take from it the last mechanical characteristic which Lorentz had
still left it."

He is talking here about "aether drift". That does not imply that
there are no "mechanical" properties.

Einstein is most certainly saying there are no ``mechanical''
properties. From earlier in the essay:

``As to the mechanical nature of the Lorentzian ether, it may be
said of it, in a somewhat playful spirit, that immobility is the only
mechanical property of which it has not been deprived by H. A.
Lorentz. It may be added that the whole change in the conception
of the ether which the special theory of relativity brought about,
consisted in taking away from the ether its last mechanical quality,
namely, its immobility.''

Then later the quote above:

``More careful reflection teaches us, however, that the special theory
of relativity does not compel us to deny ether. We may assume the
existence of an ether; only we must give up ascribing a definite
state of motion to it, i.e. we must by abstraction take from it the
last mechanical characteristic which Lorentz had still left it.''

Either that or Einstein isn't being very consistent.

Sure he is. He is saying that empty space has properties -- metrical
(there's a notion of distance) and geometrical (there's a notion of
curvature), and as such can be thought of as a sort of ``ether,'' sice,
as he writes,

``To deny the ether is ultimately to assume that empty space has
no physical qualities whatever. The fundamental facts of mechanics
do not harmonize with this view.''

But he also stresses that these physical properties are not in any sense
mechanical, and that this ``ether'' is therefore very different from
earlier ideas of ether as a medium.

Whether you want to call empty space in relativity ``ether'' or not is
a matter of semantics. But if you choose to use that term, you need
to be careful not to let misleading connotations from earlier usages
slip in.

Steve Carlip

wrote:

Either that or Einstein isn't being very consistent.

Sure he is. He is saying that empty space has properties -- metrical
(there's a notion of distance) and geometrical (there's a notion of
curvature), and as such can be thought of as a sort of ``ether,'' sice,
as he writes,

``To deny the ether is ultimately to assume that empty space has
no physical qualities whatever. The fundamental facts of mechanics
do not harmonize with this view.''

I again point out that his discussion of Lorentz's "last mechanical
property" is that stationarity, in other words an aether drift,
which was found to not be measurable.

But he also stresses that these physical properties are not in any sense
mechanical, and that this ``ether'' is therefore very different from
earlier ideas of ether as a medium.

In a sense, but in another sense, not so. The properties of Aether
were assumed "super human" from the beginning so that if we find
that it's not an ideal gas etc. that isn't really out of line. None
of that "proves" however that space is mathematical and not in
some ultimate sense "mechanical". It only shows that in the case
of Aether drift something is going on that needs to be modeled
better. Lorentz transformations in a sense do that, but also
like Newtons theory of gravitation, it gives the right answer but
explains nothing.

Whether you want to call empty space in relativity ``ether'' or not is
a matter of semantics. But if you choose to use that term, you need
to be careful not to let misleading connotations from earlier usages
slip in.

Yes, that's true. But can there be a mechanical model correctly
generating relativity space? I'm guessing that there can and
even more, within such a model could lurk a "theory of everything".
I'm always very suspicious of mathematics being used as an explanation!
Sure, it's a wonderful way to predict quantities (provided mathematical
model limits aren't exceeded), but I get more than just a little tired
of every science program on PBS saying how Newton "explained"
gravity. Newton himself said he did no such thing and suggested
that the "explanation" gravity might lie within some kind
"impulses" in the aether.

bjacoby

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Due to SPAM innundation above address is turned off!

Subject: Question about Ether and Space-Time. What's the difference?
From:
Date: 12/18/03 1:08 AM Central Standard Time
Message-id:
============
Let me jump in without dealing with any particular state of the discussion.

A quote of Einstein from the Project Gutenberg is:
http://www.gutenberg.net/etext05/slrtv10.txt

"The space-time theory and the kinematics of the special theory of relativity
were modelled on the Maxwell-Lorentz theory of the electromagnetic field. This
theory therefore satisfies the conditions of the special theory of relativity,
but when viewed from the latter it acquires a novel aspect. For if K be a
system of co-ordinates relatively to which the Lorentzian ether is at rest, the
Maxwell-Lorentz equations are valid primarily with reference to K. But by the
special theory of relativity the same equations without any change of meaning
also hold in relation to any new system of
co-ordinates K' which is moving in uniform translation relatively to K. Now
comes the anxious question:--Why must I in the theory
distinguish the K system above all K' systems, which are physically equivalent
to it in all respects, by assuming that the ether is at rest relatively to the
K system? For the theoretician such an asymmetry in the theoretical structure,
with no corresponding
asymmetry in the system of experience, is intolerable. If we assume the ether
to be at rest relatively to K, but in motion relatively to K', the physical
equivalence of K and K' seems to me from the logical standpoint, not indeed
downright incorrect,but nevertheless inacceptable."

Notice the confusion of the man. He asks, "Why must I in the theory distinguish
the K system above all K' systems, which are physically equivalent to it in all
respects, by assuming that the ether is at rest relatively to the K system?"

If he is talking about the Lorentz theory, the K system is unique in that it is
defined to be at rest in the ether. So if he wishes to follow the teaching of
Lorentz, K is unique and the various K's are not. Of course, the Lorentz theory
will predict that rods shorten and clocks run slow 'at speed'. (What I call the
'physics of fast motion', as opposed to SR.) And the Lorentz theory will then
'explain' his results as a 'simpler' way to compute certain results, though not
fully 'correct' in that they cannot distinguish between K and K'. It will also
predict that certain types of experiments will never, by themselves, show speed
relative to the ether. It will not predict that other types of experiments,
such as say measuring the Doppler of the CMBR, can not be interpreted as giving
a measure of speed through the ether, thus calibrating the speed of the earths
K' relative to the ether and allowing all other K' speed to be measured
relative to that.

If, on the other hand, he does not follow Lorentz, he if free to follow his
idea to where it leads. Of course, he would have been aware that his results
would not EVER allow the distinction between K and K', which was already
allowed for by Lorentz. But he in not free to insert: "-Why must I in the
theory distinguish the K system above all K' systems, which are physically
equivalent to it in all respects" unless he recognizes that that is only true
in 'his' theory. His system has found a way to throw the baby out with the bath
water. If his system has no way to distinguish between K and K', well, so be
it. K and K' are not physically equivalent in all respects in the Lorentzian
system, only in the SR system. So the price of his 'simplification' of
calculations is to be unable to incorporate the value of 'speed through ether'
that may be measured by some new technique. That is one of the most significant
results of the SR system. Both Lorentzian ether and Einsteinian SR let you
design a cyclotron. Only one lets your incorporate a 'speed through ether'
measurement in anything. The steps from Newton to Lorentz to Einstein were not
steps of increasing ability to define the world. The SR theory took one step
back.

When he complains that: "For the theoretician such an asymmetry in the
theoretical structure, with no corresponding
asymmetry in the system of experience, is intolerable." he doth protest too
much. The theoretician cannot expect that experimental science has progressed
so far ahead of him that all that is so has already been discovered. His
'experience' may be that of someone who has not yet 'been around the block' and
hence is not a trustworthy criterian of 'what is so'. The existance today of
the CMBR asymetry is a perfect example of a possible 'asymmetry in the system
of experience' that exists today but that did not exist when he was using his
lack of asymmetry exerience as a proof that an asymetry did not exist.

etc. etc. etc.

End of 'Let me jump in . . ."

Earl Gasner


============
wrote:

That's not what Einstein said at all. You can find the full text,
thanks to Project Gutenberg, at
http://www.gutenberg.net/etext05/slrtv10.txt


The full quote: "There are weighty arguements to be adduced in favor of
the aether hypothesis. To deny Aether is ultimately to assume that
that physical space has no physical qualities whatever. The fundamental
facts or mechanics do not harmonize with this view...according
to the general theory of relativity space is endowed with physical
qualities; in this sense, therefore, there exists an aether. According
to the General Theory of Relativity space without aether is unthinkable."

Another quote from the same essay:

"We may assume the existence of an ether; only we must give up
ascribing a definite state of motion to it, i.e. we must by abstraction
take from it the last mechanical characteristic which Lorentz had
still left it."

He is talking here about "aether drift". That does not imply that
there are no "mechanical" properties. Either that or Einstein isn't
being very consistent.

Today the aether model has simply been thrown out and replaced
with pure mathematics. Lame excuses, like things being "unknowable"
abound. Let's see. Einstein thought quantum mechanics was bunk
and aether essential! Gosh, I may be a kook, but I seem to be
in some pretty good company!

bjacoby
(Just call me Min jr.)
--
Due to SPAM innundation above address is turned off!