Question about the universe structure?

In summary: And then, when you put inflation into the mix, you recognize that the overall spatial curvature that we observe is a combination of the overall spatial curvature of the inflating patch plus a correction due to perturbations early-on during inflation. Since those perturbations are...not randomly distributed, they tend to cluster in certain places...which is why we see concentrations of galaxies, for example.
  • #1
Hyperspace2
85
1
question about the universe structure?

I have a question.
Does universe consist curved spacetime everywhere? ,


I believe there are plenty of flat spacetime, isn't it? . If it is so then eveywhere worm hole is not possible isn't it?
 
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  • #2


According to current cosmological models, the curvature of spacetime is small, nonzero, and nearly constant on large scales. On smaller scales, you have, e.g., the region near the Earth's surface, which is more highly curved.

Hyperspace2 said:
I believe there are plenty of flat spacetime, isn't it? .
Perfectly flat? Not likely.

Hyperspace2 said:
If it is so then eveywhere worm hole is not possible isn't it?
How does this connect logically to the rest of your post?
 
  • #3


bcrowell said:
How does this connect logically to the rest of your post?

worm hole connects the shortest distance between two points in curved spacetime.
If majority of spacetime tends to be flat ,then we cannot drill that worm hole everywhere,isn't it ? or can we?
 
  • #4


bcrowell said:
According to current cosmological models, the curvature of spacetime is small, nonzero, and nearly constant on large scales.
Not correct. The curvature of space is extremely small on large scales. There is very significant curvature of space-time, however, which we see as the expansion of the universe.

That said, we do not expect our universe to be, on average, perfectly flat (in terms of space). Our current observations show it's flat to within about a percent or so. But there is expected to be some deviation we can't (yet) detect.
 
  • #5


Chalnoth said:
Not correct. The curvature of space is extremely small on large scales. There is very significant curvature of space-time, however, which we see as the expansion of the universe.

That said, we do not expect our universe to be, on average, perfectly flat (in terms of space). Our current observations show it's flat to within about a percent or so. But there is expected to be some deviation we can't (yet) detect.

if much percent of space was flat than , worm hole was not possible,isn't it?
Should we inspect before we make a hole.

I mean Dr Ronald L. Mallett couldnot make his wormhole in his laboratory, did he have to inspect some place to actually create wormhole.
 
  • #6


Hyperspace2 said:
if much percent of space was flat than , worm hole was not possible,isn't it?
There are other reasons to suspect that such wormholes don't exist, but the overall spatial curvature isn't one of them.
 
  • #7


Chalnoth said:
bcrowell said:
According to current cosmological models, the curvature of spacetime is small, nonzero, and nearly constant on large scales.
Not correct. The curvature of space is extremely small on large scales. There is very significant curvature of space-time, however, which we see as the expansion of the universe.
I think that bcrowell's statement is entirely correct. Curvature of spacetime is significant, but still small (i.e. large curvature radius).
 
  • #8


Ich said:
I think that bcrowell's statement is entirely correct. Curvature of spacetime is significant, but still small (i.e. large curvature radius).
The point is as you go to large enough scales, the curvature radius starts to become significant compared to the scales you're considering.

I suppose there is an intermediate set of scales where the space-time curvature can be considered small, though. At least on relatively short time scales.
 
  • #9


,then we cannot drill that worm hole everywhere,isn't it ? or can we?
You can't drill wormholes.

So I was under the impression that measuring the curvature to be about 1% was simply our limited technology. Is it definitely known that the universe could not possibly be flat, and why/how?
 
  • #10


hadsed said:
So I was under the impression that measuring the curvature to be about 1% was simply our limited technology. Is it definitely known that the universe could not possibly be flat, and why/how?
The first thing to point out is that the curvature is represented as a real number. This means that as long as you have physics which don't predict that the value must be some specific number, any specific number you might choose actually has zero probability of being the real value of the curvature.

Imagine, for instance, that we had initial physics that made for a probability that the curvature could be anywhere from -0.1 to 0.1 with equal probability in that range. The probability for any set of values being true is:

(# of values that match the condition)/(total # of possible values)

The problem here is that there is only one possible value that matches the condition of zero curvature, but there are actually an infinite number of potential values for the curvature between -0.1 and 0.1. In fact, there are an infinite number of potential values for the curvature between -0.00000000000001 and 0.00000000000001.

And then, when you put inflation into the mix, you recognize that the overall spatial curvature that we observe is a combination of the overall spatial curvature of the inflating patch plus a correction due to perturbations early-on during inflation. Since those perturbations are random, the curvature we measure just won't be identically zero, even if it just so happens that there is some weird physics that sets the overall curvature to zero identically.
 
  • #11


hadsed said:
You can't drill wormholes.

why?
 

What is the current understanding of the structure of the universe?

The current understanding of the structure of the universe is that it consists of galaxies, which are clusters of stars, gas, and dust held together by gravity. These galaxies are organized into larger structures known as galaxy clusters and superclusters. The universe also contains vast expanses of empty space.

What is the shape of the universe?

The shape of the universe is a hotly debated topic in cosmology. Some theories suggest that the universe is flat, meaning that parallel lines will never intersect. Other theories propose a curved universe, such as a sphere or a saddle shape. Currently, there is not enough evidence to determine the exact shape of the universe.

How does dark matter and dark energy affect the structure of the universe?

Dark matter and dark energy are two mysterious components of the universe that have a significant impact on its structure. Dark matter is thought to make up about 85% of the total mass of the universe and helps hold galaxies together through its gravitational pull. Dark energy, on the other hand, is believed to be responsible for the accelerating expansion of the universe.

What is the role of the cosmic microwave background in understanding the structure of the universe?

The cosmic microwave background (CMB) is the remnant radiation from the early universe, which can be observed in all directions of space. By studying the properties of the CMB, scientists can gain insights into the composition and evolution of the universe. It also provides evidence for the Big Bang theory and supports the idea of an expanding universe.

How does the structure of the universe change over time?

The structure of the universe is constantly evolving. In the early stages, the universe was a hot and dense plasma of particles that expanded rapidly. As the universe cooled, particles began to clump together, eventually forming stars, galaxies, and larger structures. The expansion of the universe also continues to shape its structure, as galaxies move further apart from each other due to the force of dark energy.

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