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- Thread starter BigBang1234
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Someone is wrong.Someone told me that spacetime is a matter.

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tiny-tim

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Hi BigBang1234! Welcome to PF!

If it is not mass or energy, tell me what is it.

Spacetime is a space.

It has curvature (that's only "intrinsic curvature", it doesn't mean that it's contained in some bigger space in which it has a physical curvature).

It has nothing but curvature.

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In GR space geometry is shaped by matter, but in some quantum gravity theories space and matter can be described in terms of each other

http://arxiv.org/PS_cache/arxiv/pdf/1006/1006.2230v2.pdf [Broken]

Abstract. In this paper we will discuss the question how matter emerges from

space. For that purpose we consider the smoothness structure as underlying

structure of the spacetime manifold. The smoothness structure depends on an

infinite structure – the Casson handle – representing the failure to smoothly

embed a disc without self-intersections (immersed disc). By using the Weierstrass

representation, we are able to show that the immersed discs are represented by

spinors fulfilling the Dirac equation and leading to a mass-less Dirac term in the

Einstein-Hilbert action. Between the immersed discs, there are “connecting tubes”

which are realized by an action term of a gauge field. Both terms are genuinely

geometrical and characterized by the mean curvature of the components of the

Casson handle. We also discuss the gauge group of the theory.

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I love to try to answer this question in part because it's interesting and also because every time we discuss it and I say "Spacetime IS something", meaning "it sure SEEMS like something, lots of the gurus here get apoplectic...that is excitedly angry .... because its not a conventional answer...but we can describe some attributes of spacetime that bring home how interesting it is.

Tinytim's post probably reflects conventional, current, science. But a lot that is conventional science is incomplete. You could also call spacetime a model:

http://en.wikipedia.org/wiki/Spacetime

meaning how we choose to represent space and time, and the discussion has other interesting points to make as well.

Spacetime is conventional three dimensional Eucledian space plus time (not a very satisfying answer,of course). Even if someone said "space is a matter" nobody knows what matter is either, any more than we know what time or gravity is.

Suggest you search the forums here with "what is spacetime",,,you'll finds lots of threads (discussions).

Seems like space requires time, and that spacetime IS actually something with these among its characteristics:

measured distances and elapsed times depend on your velocity and position,

it expands and that expansion is accelerating,

it seems to have horizons,

it can curve (change shape due to mass,energy or pressure)

always seems to have quantum fluctuations (quantum foam, even at zero degrees absolute)

maybe dark energy (we sure don't know what THAT is either,

some symmetries,

maybe some singularities (big bang, inside black holes),

an interval (a combination of space and time, see spacetime interval in the above reference).

Another way to think of spacetime is that it apparently originated from a big bang...in that view, some extremely high unstable entity (a bang) gave birth to mass, energy,time,distance(space) and an expanding universe. But why THESE particular entities popped out, and not others or not in different combinations, nobody knows.

Tinytim's post probably reflects conventional, current, science. But a lot that is conventional science is incomplete. You could also call spacetime a model:

http://en.wikipedia.org/wiki/Spacetime

meaning how we choose to represent space and time, and the discussion has other interesting points to make as well.

Spacetime is conventional three dimensional Eucledian space plus time (not a very satisfying answer,of course). Even if someone said "space is a matter" nobody knows what matter is either, any more than we know what time or gravity is.

Suggest you search the forums here with "what is spacetime",,,you'll finds lots of threads (discussions).

Seems like space requires time, and that spacetime IS actually something with these among its characteristics:

measured distances and elapsed times depend on your velocity and position,

it expands and that expansion is accelerating,

it seems to have horizons,

it can curve (change shape due to mass,energy or pressure)

always seems to have quantum fluctuations (quantum foam, even at zero degrees absolute)

maybe dark energy (we sure don't know what THAT is either,

some symmetries,

maybe some singularities (big bang, inside black holes),

an interval (a combination of space and time, see spacetime interval in the above reference).

Another way to think of spacetime is that it apparently originated from a big bang...in that view, some extremely high unstable entity (a bang) gave birth to mass, energy,time,distance(space) and an expanding universe. But why THESE particular entities popped out, and not others or not in different combinations, nobody knows.

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But energy is not space, and is only more like a medium it travels through. I don't see anywhere in the paper where the connection we know of between space and energy is even used (SR).

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But energy is not space, and is only more like a medium it travels through. I don't see anywhere in the paper where the connection we know of between space and energy is even used (SR).

Particles are modeled as fields, and the word "emerge" has more a meaning of equivalence(in description) than the same. Particles are also "equated" with energy . There is no accepted theory of modeling particle as photons(energy). only, there is the old "electromagnetic mass" theory by Lorentz which is not accepted yet, maybe in the future ,who knows.

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