[chimera (OP)]

Rene Descartes, the man who gave us our ubiquitous XYZ spatial coordinate system, and therefore no fool, strangely did not believe in empty space, or vacuums.

Now this is depicted in the scientific history books as something of a buffoonish attitude, but I think he may have a point, even supported by a bit of modern knowledge.

What he said was that there was no such thing as empty space, only matter.

Now think on what the big bang theory tells us, it was an expanding sphere of a very isotropic gas or plasma of incredible temperature. What's outside of it, is not known. Inside the volume of hot gas, which cools down, you see the gas clumping to matter, evacuating the space formerly occupied by the hot gas.

In that sense he is correct, namely that the only place matter can be, is within the space not occupied at that point by any other matter. Therefore, space is just the temporary absence of matter, but essentially still matter.

And indeed, our present finding indeed tells us raw interstellar vacuum, many orders of magnitude better than even our best artificial vacuum, is not empty - cannot be truly empty even, only temporarily.

'True nothingness' is probably that which lies outside it, but vacuum in that sense is indeed nothing but a forced disequilibrium in the distribution of matter.

Strange, eh? []

[DoctorBeaver]

quote:In that sense he is correct, namely that the only place matter can be, is within the space not occupied at that point by any other matter. Therefore, space is just the temporary absence of matter, but essentially still matter.

So could you say that land is just the temporary absence of water, but essentially still water? Or that where a man is standing is only the temporary absence of an African land snail, but essentially still occupied by an African land snail?
Sorry, but that is just twaddle & not even logically coherent. It doesn't logically follow that empty space is empty because it is the "temporary absence of matter". In fact it's exactly the opposite. The expansion of the universe is creating more "empty space" & if the expansion continues the less likely it is that there will be matter to fill all the empty space. The concept you put forward really isn't even deserving of an erudite reply.
Descartes was a good thinker so either he had an aberrant moment when he came up with that or you've incorrectly interpreted what he said

[chimera (OP)]

quote:Originally posted by DoctorBeaver

Descartes was a good thinker so either he had an aberrant moment when he came up with that or you've incorrectly interpreted what he said

No, I think I interpret him quite correctly, and that his theory in this case is rejected in some kind of reflex, because eithere it is too simple, too counterintuitive, or both. But again, that is to my best knowledge, exactly what he meant.

Your counterexamples are twaddle, of course. We're talking first principles here, not snails. At no point of the big bang vacuum was created, more like 'evacuated' later, by the accumulation of matter. So you go from a hogomenous gas to a very thin lumpy one.

[DoctorBeaver]

quote:At no point of the big bang vacuum was created, more like 'evacuated' later, by the accumulation of matter. So you go from a hogomenous gas to a very thin lumpy one.

That is more-or-less what I was getting at. Once a certain area of space has been evacuated, because of the greater scattering of the contents the less likely it is to be refilled. The longer the expansion continues without more matter being created, the more likely it is that the evacuation will be permanent.

& yes I know my examples were twaddle. Reductio ad absurdam. []

I wasn't trying to demean your intelligence, by the way. Descartes' theory may well have seemed logical given the knowledge of the universe at that time. But now we know it's expanding it just doesn't make sense anymore. Or is it me who's missing the point?

[chimera (OP)]

quote:Originally posted by DoctorBeaver

Or is it me who's missing the point?

I think so. Expansion aside, there is a difference between 'vacuum' and 'nothing'. What Descartes said, was that if you go from a gas to evacuated space, since all the matter and energy has lumped into stars and planets and more dense clouds of gas, the remainder is still not really 'empty'.

Now if this dilute gas aka vacuum is expanding, that could well be because however thin, it is still of higher pressure than what's outside of this universe, namely real nothingness, of no pressure, meaning the universe might even have 'surface tension'. Note that these expanses of thin gas would expand much faster than the solidified matter, if at all.

Come to think of it, that's not far off from what's observed.

[DoctorBeaver]

Now that makes more sense. I think it was the phrase "temporary evacuation" that was throwing me off track.

[chimera (OP)]

Now the main mental switch is accepting the fact, that what we see as vacuum, is only an absence of matter. It once was occupied by it, and can be again. At no point in time of this universe 'space' was essentially different from 'matter'. The opposition or dichotomy is a false one. Even talking about 'space-time' does not really make the coin drop, in that sense.

Space is just matter on vacation, to paraphrase my sig...

[DoctorBeaver]

Now you've done it again. "...that what we see as vacuum, is only an absence of matter. It once was occupied by it, and can be again."
Yes, it can be, but the more "dilute" space becomes, the less likely it is that any given area will be re-occupied.
I fully appreciate the difference between vacuum & nothingness, but I don't see that as the issue except insofar as a vacuum will always be at a greater pressure than nothingness

[gsmollin]

I thought twice about jumping in on this good debate, but I can't resist. You two remind me of 17th century philosophers, except you haven't brought up angels and pinheads yet...

The debate about space and matter stretches way back, and our present philosophy can be blamed on Isaac Newton. It was he who declared space "absolute". He pissed off a lot of people in the Royal Society at that time, who thought that space could not be absolute, but only relative between material objects. They were right, of course, but nobody but Newton was in a position to describe it all in quantitative terms. So he did, and space became absolute, relative to the "fixed stars". The stars aren't fixed, and even Einstein didn't know that, but at least he had the imagination to throw off the shackles of Newtonian fixed-space, and describe it in relative terms.

Both of you should read Einstein's book, "Relativity". It goes through this in a lot of detail, with "mathematics at the level of a university matriculation exam" (A. E.). He describes most of your debate points, and it is a very good read.

[chimera (OP)]

quote:Originally posted by DoctorBeaver

Now you've done it again. "...that what we see as vacuum, is only an absence of matter. It once was occupied by it, and can be again."
Yes, it can be, but the more "dilute" space becomes, the less likely it is that any given area will be re-occupied.
I fully appreciate the difference between vacuum & nothingness, but I don't see that as the issue except insofar as a vacuum will always be at a greater pressure than nothingness

[sorry gsmollin, we're on a roll here, and I'll check out the book]

True, you cannot say there WILL be matter, but more importantly, it is the only place for matter (and energy, and light) to go TO, if you see what I mean. This very thin soup is still a far cry of true nothingness, perhaps even light cannot cross 'true nothingness' for lack of substrate, bringing back the whole discussion in fact about 'aether' with the vacuum taking that epithet  nolens volens, if you will.

And remember, our lab vacuums are not even a billionth as empty as deep space. We cannot do it, let alone 'tear a rip' in the fabric of' 'reality' or spacetime. That would require enough force to not only overcome gravity, but also you'd have to push two entire 'halves' of the universe apart over a tiny space, but they might as well be like the most gigantic Magdenburger half-globes, and I don't think even 50 kazillion horses could pull it off.

But again, I think it might be possible light does not travel in true nothingness, and likewise matter can only go where it once was, in that sense, to 'vacuum' space.

[and frankly, I never heard Einstein about what's *outside* our turf]

[chimera (OP)]

quote:Originally posted by gsmollin

I thought twice about jumping in on this good debate, but I can't resist. You two remind me of 17th century philosophers, except you haven't brought up angels and pinheads yet...

Just on a side-note: we *are* discussing a 17th century philosopher, and angels and pinheads were dediced at the Synod of Nicae in the 4th century, if I remember correctly, and I think they agreed on the number 133.

Angels that is, that could dance on the head of a pin, great controversy in early Christianity, needles(s) to say.

[DoctorBeaver]

quote:But again, I think it might be possible light does not travel in true nothingness, and likewise matter can only go where it once was, in that sense, to 'vacuum' space.

Light cannot travel through nothingess because the very fact that a photon is there means that it cannot be empty. It therefore must become a vacuum as soon as the photon enters it.

I met a some Angels at a rock concert once & I sure-as-Hell wouldn't want to try putting any of them on a pinhead!

[gsmollin]

Once again, philosophers, I must kibbitz. Quantum mechanics requires a Newtonian space, with absolute timelines and coordinates. Relativity requires a 4-dimensional continuum, no absolutes. Mixing these two has led numerous mathmaticians and physicists to dance on the head of a pin. I don't know if any angels got off, but you can just get wrapped around an axle with this, like verybody else has, so far.

[DoctorBeaver]

gsmolin - there's nothing unwarranted or intrusive about your comments (yes, I know what kibbitz means! [:p])

quote:Relativity requires a 4-dimensional continuum, no absolutes

Does Riemann geometry not have co-ordinates? I can understand that there would be difficulties with it but I would have thought not impossible

[chimera (OP)]

quote:Originally posted by gsmollin

 Relativity requires a 4-dimensional continuum, no absolutes.

Isn't the speed of light an absolute?

And is a 4-dimensional space not just 3-dimensional space doing a rerun, slightly different this time? I mean, it's the same 3 dimensions, just later. Time is just a sequence counter, in that sense. Not a real dimension always present, like the other 3. Those other three are ALWAYS present. You cannot have something 2D within this universe, it will always have SOME thickness, and therefore a 3d dimension. But 'time' you can leave out of quite a few models. Only when you wish to show a *process* time comes into the picture.

[DoctorBeaver]

quote:And is a 4-dimensional space not just 3-dimensional space doing a rerun, slightly different this time? I mean, it's the same 3 dimensions, just later. Time is just a sequence counter, in that sense. Not a real dimension always present, like the other 3. Those other three are ALWAYS present

Imagine a 2D object being moved along a 3rd dimension by an external force. The 2D object could not percieve that force as such as it exists in a dimension unaccessible to the object. The object wouldn't realise it was actually moving but things around it would change as a result of that movement.
Now, in my analogy, substitute a human being for the 2D object and have Time as a 4th D through which we are being moved by an external force. We can easily percieve & understand the 3rd D which was so mysterious to the 2D object and it's Time (the 4th D) which presents us with conceptual problems. It's quite possible that the 4th D is always present, just that we can't percieve it.
Think also of a photon. It travels at the speed of light which, I believe, as a result of time dilation means that from its perspective the entire life of the universe passes in zero time. For it, the 4th D doesn't exist. (Something in the murky depths of my brain tells me that the photon situation has some profound importance but the concept won't quite manifest itself yet.I'll probably wake up at 3am & shout "Eureka!")

[DoctorBeaver]

I'm thinking out loud here so please forgive if it ends up being total rubbish.

Gravity distorts spacetime & in intense gravitational fields time goes completely mental. Rather than time merely being affected by gravity, could it be a function of gravity or maybe a consequence of gravitational effects?
In my previous reply I referred to a hypothetical force propelling us through time. Gravity affects the 3 dimensions we are aware of & the 4th which we postulate, so what if gravity exists in a dimension other than 1 of those 4 yet exerts an influence on them?
It's not only gravity that makes time go silly, relativistic speeds do the same. Returning to my 2D object, there could be a variety of factors that could cause it to move through a 3rd D - e.g. a breeze, someone pushing with their finger, etc.. Einstein said that gravity & acceleration are the same thing - who am I to argue with him!. But what if they're not? What if they are merely 2 identical effects of different phenomena? The 2D object might say that breeze and a pushing-finger are the same thing as the effect of both is identical: but we can understand that they're totally different.
erm... I'm not sure where I'm going with this. I'll have to think about it a bit more. But I'll leave this post here so people have the chance to point & laugh at me. [V]

[chimera (OP)]

See, how picking up where 17th century geniuses left off aint so bad. It really makes you *think*.

Currently reading Leibniz's Monadologies. Weird, but very interesting.

(found that tip in one of Lee Smolin's books, who in turn got that advice from Julian Barbour, who's some physicist's guru of sorts - 'read Leibniz')

[DoctorBeaver]

Are you saying that I'm an anachronism?

[gsmollin]

quote:Originally posted by chimera

quote:Originally posted by gsmollin

 Relativity requires a 4-dimensional continuum, no absolutes.

Isn't the speed of light an absolute?

And is a 4-dimensional space not just 3-dimensional space doing a rerun, slightly different this time? I mean, it's the same 3 dimensions, just later. Time is just a sequence counter, in that sense. Not a real dimension always present, like the other 3. Those other three are ALWAYS present. You cannot have something 2D within this universe, it will always have SOME thickness, and therefore a 3d dimension. But 'time' you can leave out of quite a few models. Only when you wish to show a *process* time comes into the picture.

The speed of light is an absolute. The 4 dimensions are not. Time is not a sequence counter. That is the Newtonian viewpoint. You can't leave time out, except in mathematical models. Physically its always 4-D.  Different viewpoints of the same events all have their own clocks running at different speeds, and will report a different process. You can always take a "snapshot", but the snapshot had to occur at a "time". A snapshot at a different time shows a different picture.