[cosmic rain]

Physicists now admit they know the universe is flat. They have reasoned that only a flat universe with equal amounts of both positive energy and negative gravity can come from nothing. They say the rules for quantum mechanics allow for a universe to exist from nothing, based on the prediction that if opposite A is true, then eventually opposite B will also be true. Quantum physicists have never been able to explain why there is even distribution in the quantum theory, and the cosmologists have never been able to explain the uneven distribution of energy in the big bang. They have been able to determine that 98% of the materials needed for a successful universe came out of the big bang in the first several minutes, while the rest of the big bang poured out radiation for many thousands of years.

Scientists like to describe nothing as the absence of space, the absence of time, or the absence of anything associated as information. However there are differences of opinion for what the real definition of nothing is, and I guess it depends on how you want to look at it, literally. One renowned physicist doesn't believe in the absence of space as nothing. He believes nothing to be space with nothing in it. He theorizes that all of empty space can have weight, which can cause a vacuum fluctuation, and initiate a big bang. This is a scenario which can avoid many questions; one of them being how do you explain what appears to be precision based mechanics in nature? It's not just the quantum theory and the distribution of energy in the big bang that needs further explanation; it's the question of how nature can provide equal amounts of both positive and negative in a flat universe from nothing. One has to ask, can a vacuum fluctuation do all of that?

[IM Egdall]

I think this whole "flat universe" notion is a simplification. It is based on observations of the observable universe. What about the rest of the universe, the part where objects are so far away the light has not reached us yet? Is the whole universe flat? Or is it just the part we can observe?

Form what I have read, it is not at all clear that the entire universe is flat. It is more likely curved in some way. So all this talk about positive energy being canceled by negative gravity in a flat universe may not apply to the universe as a whole.

This post has been edited by IM Egdall: 3 November 2011 - 03:14 PM

[Mystery111]

IM Egdall, on 3 November 2011 - 03:13 PM, said:

I think this whole "flat universe" notion is a simplification. It is based on observations of the observable universe. What about the rest of the universe, the part where objects are so far away the light has not reached us yet? Is the whole universe flat? Or is it just the part we can observe?

Form what I have read, it is not at all clear that the entire universe is flat. It is more likely curved in some way. So all this talk about positive energy being canceled by negative gravity in a flat universe may not apply to the universe as a whole.

It is a simplification. The truth is it is almost flat, and curvature will show up when matter is present in a region. Overall it just means the matter in our universe is very diluted and also means that at some point in it's history it underwent a rapid acceleration. This would have had to have been true if indeed we are to believe everything came from a finite past, a very small region where the big bang originated. This name is often amusing. As Fred Hoyle coined it to mirror the innacuracy of how we percieved it, it was niether large nor a bang.

[questionposter]

Mystery111, on 3 November 2011 - 07:17 PM, said:

It is a simplification. The truth is it is almost flat, and curvature will show up when matter is present in a region. Overall it just means the matter in our universe is very diluted and also means that at some point in it's history it underwent a rapid acceleration. This would have had to have been true if indeed we are to believe everything came from a finite past, a very small region where the big bang originated. This name is often amusing. As Fred Hoyle coined it to mirror the innacuracy of how we percieved it, it was niether large nor a bang.

The real truth is that space doesn't naturally curve unless there is something to bend it. That's why in relatively not curved space, the angles in a triangle add up to exactly 180 degrees rather than more or less, because of space was curved negatively, then the angles in a triangle would appear to be less than 180 degrees, and if it was curved positively, the angles in a triangle would appear to be more than 180 degrees in the absence of a lot of mass to distort space a lot.

However, this flat space could go on infinitely, no one knows, we definitely don't know a lot about the whole universe, all we know as what we can measure.

This post has been edited by questionposter: 4 November 2011 - 01:27 AM

[Mystery111]

questionposter, on 4 November 2011 - 01:26 AM, said:

The real truth is that space doesn't naturally curve unless there is something to bend it. That's why in relatively not curved space, the angles in a triangle add up to exactly 180 degrees rather than more or less, because of space was curved negatively, then the angles in a triangle would appear to be less than 180 degrees, and if it was curved positively, the angles in a triangle would appear to be more than 180 degrees in the absence of a lot of mass to distort space a lot.

However, this flat space could go on infinitely, no one knows, we definitely don't know a lot about the whole universe, all we know as what we can measure.

We will begin with a standard wave equation:



This is a wave equation. Using natural units and expressing this wave equation in three dimensions



To make it into a tensorial equation, we can take to be so that [LaTeX Error: Syntax error] and differentiate as:



To work out the covariant derivative involves Christoffel Symbols by definition. This equation will describe the path of a photon for instance in a curved spacetime geodesic. They are models of parallel transport.

This post has been edited by Mystery111: 4 November 2011 - 01:42 AM

[questionposter]

Mystery111, on 4 November 2011 - 01:40 AM, said:

We will begin with a standard wave equation:



This is a wave equation. Using natural units and expressing this wave equation in three dimensions



To make it into a tensorial equation, we can take to be so that [LaTeX Error: Syntax error] and differentiate as:



To work out the covariant derivative involves Christoffel Symbols by definition. This equation will describe the path of a photon for instance in a curved spacetime geodesic. They are models of parallel transport.

But waves can also be described as a simple sine wave and more often are, and in fact, sine waves come from a unit circle, and in a unit circle, the angles of a triangle add up to 180 degrees. What your describing is I think the probability of particles, and probability is different than angles and length.

Also, did you just google "wave equations" and click on the first link and post the equations just to make yourself look smart?

http://en.wikipedia....i/Wave_equation

Because that entire post isn't very helpful for me to understand why space itself is curved unless your suggesting that the fabric of space itself is a wave and photons are part of that waving spacial fabric, which there isn't much evidence for if any at all, but perhaps some expert could explain it if I'm not getting something.

This post has been edited by questionposter: 4 November 2011 - 02:44 AM

[Mystery111]

In General Relativity, the ''connection'' is due to what is called the Christoffel Symbol . It is what is called an ''affine connection'' which defines the ability to have parallel transport i.e, curved spacetime.

questionposter, on 4 November 2011 - 01:26 AM, said:

The real truth is that space doesn't naturally curve unless there is something to bend it.

Also this isn't true. The Einstein Field equations allows you to have a zero-mass but non-zero curvature.

[Realitycheck]

Are you referring to the effect of a cosmological constant?

[questionposter]

Mystery111, on 4 November 2011 - 03:42 AM, said:

In General Relativity, the ''connection'' is due to what is called the Christoffel Symbol . It is what is called an ''affine connection'' which defines the ability to have parallel transport i.e, curved spacetime.



Also this isn't true. The Einstein Field equations allows you to have a zero-mass but non-zero curvature.

In that theory isn't space still being curved from mass and energy? I would imagine that if nothing is immediately around you then the only reason space would curve if because the force of gravity never dissipates to 0 or maybe because of photons.

Also, I still don't get the point of your equations. The fabric of space curves sometimes noticeably and gravity dissipates like a wave. How does that mean the fabric of space wouldn't be flat without anything in it?

Or are you trying to suggest it will never be flat because there will always be gravity and light to effect space wherever we go?

This post has been edited by questionposter: 4 November 2011 - 12:41 PM

[Mystery111]

Realitycheck, on 4 November 2011 - 04:46 AM, said:

Are you referring to the effect of a cosmological constant?

No. I am referring to Gravitational Waves. Gravitational waves are massless yet they cause curvature and propogate at lightspeed. To have no mass, this indiates the right hand side of



But does the absence of matter imply zero curvature for a metric? The answer is inexorably no.

Gravitational waves are not trivial, where the Ricci tensor is zero everywhere, but the Reimann tensor is not so it's not always the case you can deal with a massless universe and no curvature.

This post has been edited by Mystery111: 4 November 2011 - 01:53 PM

[IM Egdall]

questionposter, on 4 November 2011 - 02:41 AM, said:

http://en.wikipedia....i/Wave_equation
Because that entire post isn't very helpful for me to understand why space itself is curved unless your suggesting that the fabric of space itself is a wave and photons are part of that waving spacial fabric, which there isn't much evidence for if any at all, but perhaps some expert could explain it if I'm not getting something.

As I undersrtand it, the word "curve" or "curvature" is a mathematical term. I think it is equivalent to saying "warp" or more simply "change".

An example. Imagine two points in space - one above the other. They are a certain distance apart. Now let's place the Sun below the two points. (The points are radial points in that a line from the center of the Sun goes through the two points.)

Now because of the mass/energy of the Sun, these same two points are now farther apart (as seen from far away). This stretching of space is an example of space warp or space curvature.

Oh, and photons are also a source of this curvature, like all matter and energy. You are thinking about photons as waves, but per quantum field theory, all matter and energy particles (e.g. photons, electrons, quarks, etc.) travel like waves.

I hope this helps.

This post has been edited by IM Egdall: 4 November 2011 - 11:06 PM

[questionposter]

IM Egdall, on 4 November 2011 - 11:05 PM, said:

As I undersrtand it, the word "curve" or "curvature" is a mathematical term. I think it is equivalent to saying "warp" or more simply "change".

An example. Imagine two points in space - one above the other. They are a certain distance apart. Now let's place the Sun below the two points. (The points are radial points in that a line from the center of the Sun goes through the two points.)

Now because of the mass/energy of the Sun, these same two points are now farther apart (as seen from far away). This stretching of space is an example of space warp or space curvature.

Oh, and photons are also a source of this curvature, like all matter and energy. You are thinking about photons as waves, but per quantum field theory, all matter and energy particles (e.g. photons, electrons, quarks, etc.) travel like waves.

I hope this helps.

Right, but how does that directly suggest that space isn't flat on its own? Isn't the only way the sun could warp space in that way have to be the result of if space was otherwise flat?

This post has been edited by questionposter: 5 November 2011 - 04:58 PM