How can space warp if it is a non-thing?

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nicholas1M7

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This recent article talks about a Gravity Probe B project which confirms that Einstein was not wrong to my bafflement:

According to Einstein, in the same way that a large ball placed on a elasticated cloth stretches the fabric and causes it to sag, so planets and stars warp space-time. A marble moving along the sagging cloth will be drawn towards the ball, as the Earth is to the Sun, but not fall into it as long as it keeps moving at speed. Gravity, argued Einstein, was not an attractive force between bodies as had been previously thought.
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http://www.guardian.co.uk/science/2007/apr/15/spaceexploration.universe
 
I see now that space can indeed be anything but flat and that massive objects do indeed warp space and control the geodesic after going through some of this article by professor Stephen Hawking:

This example shows that one can not deduce the geometry of the world from first principles, as the ancient Greeks thought. Instead, one has to measure the space we live in, and find out its geometry by experiment. However, although a way to describe curved spaces, was developed by the German, George Friedrich Riemann, in 1854, it remained just a piece of mathematics for sixty years. It could describe curved spaces that existed in the abstract, but there seemed no reason why the physical space we lived in, should be curved. This came only in 1915, when Einstein put forward the General Theory of Relativity.
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http://www.hawking.org.uk/index.php/lectures/publiclectures/63
 
nicholas1M7 said:
We can now conclude that massive objects and space obviously interact but how?
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Einstein also had the same question and addressed it to some extent in a lecture at the University of Leyden, in 1920. A transcript of the address is available as a part of "Sidelights on Relativity".

Basically Einstein held that space must have some independent and intrinsic substance of its own. That substance being the basis for the interaction between space and the material objects (ponderable matter) within it.
 
Space is a thing. We just don't know what that thing is. When we say there's nothing there, we refer to there being no matter in a vacuum. But there's still space there, that we can model the behavior of. We just can't yet say what it is. That's one reason why we can define the actions of gravity but can't pinpoint what causes it, other than to say it's a property that all mass has.
 
Rhaedas said:
Space is a thing.
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I think we have reached the limits of everyday laymen's language here. Time to come up with a more precise, meaningful word than "thing."

We're in enough trouble because laymen use "theory" to mean something quite different from what it means in science. Let's not make that mistake again.
 
mass and gravity have a relationship.

gravity and spacetime have a relationship.

A spinning gravitational mass drags upon spacetime.
 
Space always has something in it, if only the tiny vacuum fluctuations, but what is space by itself if it could be? Evidently not material, but still physical, its only quantity being volume. Seems absolute.
 
Attempting to define what space IS is a fool's errand - for now. We simply do not know enough yet to be able to do that. One thing is certain, though - it's not a thing. That's a term we reserve to describe something material.

So for now, we just wait...
 
SciWriter said:
Space always has something in it, if only the tiny vacuum fluctuations, but what is space by itself if it could be? Evidently not material, but still physical, its only quantity being volume. Seems absolute.
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If you were to cling to the quantum field theory notation that a field is actually the large scale effect of lots of particles then space-time is not a place where particles are, it is particles.

For instance, Maxwell (and a few people after him) realised you can write electromagnetism in terms of a 4-potential $$A_{\mu}$$. We now view this $$A_{\mu}$$ as the vector field associated to the photon particle. Likewise for fields for the strong and weak forces. In general relativity there's the field $$g_{\mu\nu}$$ which defines the metric. If this were to be quantised then you would have it being the large scale appearance of graviton particles.

This is precisely what happens in string theory. When you compute massless closed string modes you find a set of modes which take on all the properties of $$g_{\mu\nu}$$. The graviton is a large scale effect of string oscillations, just like all other particles. This would mean that space-time is actually some kind of seething mass of strings. This isn't an isolated concept either. The branes of string theory are often thought of as somehow 'solid' objects unto themselves but infact they should be viewed on a quantised level as massive tachyon condensates, formed of a huge number of strings in a single coherent state. Space-time is just a particular case of this, as there are examples of 'space filling branes'. Loop quantum gravity takes a similar approach but it uses spin foam networks and tries to start from them and build up. It's had considerably less success.
 
Kennyc said:
Gawd I hope not. I think everyone else explained things pretty well above.
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Particular Alphanumeric's post that says space may not be empty but a foam of superstrings is really interesting. I'll investigate it further and read up on my shit.
 
SciWriter said:
Space always has something in it, if only the tiny vacuum fluctuations, but what is space by itself if it could be? Evidently not material, but still physical, its only quantity being volume. Seems absolute.
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I particularly notice your genius in saying that space is also volume.
 
Is it so then with space, matter and time together? Is space the source of matter? And is matter the embodiment of space? Are the relations between space and matter those of the universal triunity?



We know what matter is. It is energy, motion and phenomena. Its chief factor is motion. But what is space?

But What Is Space?

What is space? The answer is at once simple and complex. The simple answer is self-evident. We can all agree upon it. Space is composed of dimensions. That is certain. Space is nothing else. It consists of dimensions.

That is the clear and obvious answer. But it is not answer enough for genuine reality such as we now would reach. We must go further.
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http://www.sacred-texts.com/nth/sotu/sotu08.htm
 
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