Physical space properties questions

In summary, space-time is generally considered to be very smooth, but on the smallest scales it may be grainy due to vacuum fluctuations. It is believed that singular points in space-time will be smoothed out once a quantum theory of gravity is developed. Space-time can be considered euclidean on a macroscopic scale, but may have hidden dimensions on a microscopic scale. The topology of physical space can differ from the usual 3D space, such as a 3-torus. This may have implications for the size and curvature of the universe, but there are currently no experimental bounds on this theory.
  • #1
neginf
56
0
Is it known if space:
1. is "grainy" or smooth ?,
2. has singular points ?,
3. is like R^3 ?
 
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  • #2
the physical space i think is amazing, you know its exist but sometimes it is so abstract!
 
  • #3
Remember that space is an element/subset of space-time.

neginf said:
1. is "grainy" or smooth ?
For all intents and purposes, space-time is very smooth. On the smallest scales, we don't know; its possible that space-time is riddled with vacuum fluctuations just like quantum fields. We might need a quantum theory of gravity to find out.

neginf said:
2. has singular points ?
General relativity (GR) says that space-time does have singular points, but most people believe that's just a sign of GR's incompleteness---and once we have a good quantum theory of gravity, those singularities will be smoothed out.

neginf said:
3. is like R^3 ?
I'm not sure what you mean here. If you mean, is space euclidean---then the answer is 'asymptotically yes', but locally no---thats why we need general relativity.
If you're asking if it has three dimensions, then---at least macroscopically---yes. But there may be 'hidden' microscopic dimensions.
 
  • #4
Thank you both for the replies.

Sorry question 3 wasn't specific enough.
Could physical space have a different topology than the usual R^3 ?
 
  • #5
neginf said:
Could physical space have a different topology than the usual R^3 ?

Yes, the simplest of them being a 3-torus.
 
  • #6
aimilvping said:
the physical space i think is amazing, you know its exist but sometimes it is so abstract!

Yeah; well, apparently its invisible, transparent to light, and even weightless ! And even though it is very hard to grasp, I have managed to get some excellent samples of deep space for further experimentation.
I found space to be very stiff. Nevertheless I was able to make massive objects pass right through it unhindered ! and was even able to make it appear to bend in a graviational field ! ;))

So you can have hours of fun and experimentation...we are offering these excellent untouched samples of space for the unheard of low low price of $12.95 per cubic centimeter...(plus s & h).
Call 1-800-vacuum; hurry before the supply runs out. :)

Creator :))
 
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  • #7
Nabeshin said:
Yes, the simplest of them being a 3-torus.
How does this interplay with measurements of flatness? The universe is flat to some high percentage, so does that place limits on the curvature of such a torus (i.e. analogous to the toroidal radius of a 2-torus)? Then, if such limits were placed, would that provide limits on the size of the universe?
 
  • #8
zhermes said:
How does this interplay with measurements of flatness? The universe is flat to some high percentage, so does that place limits on the curvature of such a torus (i.e. analogous to the toroidal radius of a 2-torus)? Then, if such limits were placed, would that provide limits on the size of the universe?

The 3-Torus is actually spatially flat everywhere, so the measurements of flatness only support such a theory. One idea of how to place limits are whether or not we see radiation running along the compactified dimensions of the torus, i.e. multiple images of the same objects. This of course gives you only an lower limit to the 'radius' of the torus, but I don't know of any actual experimental bounds on this from CMB data, for example.
 
  • #9
Aw man... so much for my conceptions of understanding.

Nabeshin said:
The 3-Torus is actually spatially flat everywhere, so the measurements of flatness only support such a theory. One idea of how to place limits are whether or not we see radiation running along the compactified dimensions of the torus, i.e. multiple images of the same objects. This of course gives you only an lower limit to the 'radius' of the torus, but I don't know of any actual experimental bounds on this from CMB data, for example.

I'm going to start a new thread on this; would appreciate if you continued the conversation there Nabeshin.
 

1. What is the definition of physical space?

Physical space refers to the three-dimensional extent in which objects and events occur and have relative position and direction. It is commonly described as the area and volume occupied by matter and energy.

2. What are the three properties of physical space?

The three properties of physical space are length, width, and height. These dimensions define the size and shape of an object or space and are essential for measuring and describing its physical properties.

3. How is physical space different from abstract space?

Physical space is the tangible and measurable extent in which objects exist, while abstract space refers to the conceptual or mental understanding of space. Physical space has specific physical properties, while abstract space is a construct of the mind.

4. Can physical space be altered or changed?

Yes, physical space can be altered or changed through various processes such as movement, deformation, or transformation. For example, the arrangement of objects in a room can alter the physical space, and natural forces such as erosion can change the physical properties of landforms.

5. How do scientists study physical space?

Scientists study physical space through various fields of study, such as physics, astronomy, and geology. They use a combination of theories, experiments, and observations to understand the properties and behavior of physical space and the objects within it.

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