astronomy and cosmology

[gowtham]

every one saying that source of dark energy is black hole ,big bang,etc.. but they aren't true.since its so powerful i can't be created by black hole or from left out big bang.hence there is a central force is creating it from center of universe

[guenter]

every one saying that source of dark energy is black hole ,big bang,etc..

No one says this.

It might be advisable to read the "Overview" in Lambda - CDM model.

[JustinW]

.since its so powerful

From the way I understand dark energy, which is little, is that it's not a matter of an overly powerfull force. It's like a small force exerted over a long period of time.

Someone will probably correct me and I hope someone will if I'm thinking and repeating something that isn't true.

 

If dark energy were a powerfull force we would feel it and observe it having a larger impact on gravity.

 

I have my own question on dark energy and the shape of the universe. If dark energy is the cause of the movement we believe is expansion and the universe is believed to be flat, then the force of dark energy is directional right? If it's not exserting it's force in any particular direction, just out, then we could assume that the universe is in the shape of a sphere. But the math that supports the cosmological constant wouldn't add up, right?

 

A comment in the OP also brings a thought to mind about a centripedal force at the center of the universe. If the universe is flat and we know is moving, why couldn't we explore the possibility that we are in orbit around the center? It might explain the red shift movement if other galaxies reach a point of an orbit that has a higher trajectory.

Edited December 14, 2011 by JustinW

[DrRocket]

 

I have my own question on dark energy and the shape of the universe. If dark energy is the cause of the movement we believe is expansion and the universe is believed to be flat, then the force of dark energy is directional right? If it's not exserting it's force in any particular direction, just out, then we could assume that the universe is in the shape of a sphere. But the math that supports the cosmological constant wouldn't add up, right?

 

Dark energy is the explanation for the observed acceleration of the expansion of the universe. No one knows what the cause of the expansion itself really is. Dark energy is not really an explanation so much as a name to given to something that is not understood. To be an explanation we would need to know that dark energy truly exists and know what it is.

 

There is no "math that supports the cosmological constant." There is observational evidence that the universe is expanding and that the rate of expansion is increasing. The increasing expansion rate requires a positive cosmological constant in cosmological models that are based on general relativity. A positive cosmological constant and dark energy are essentially the same thing. There is no solid explanation for the positive cosmological constant.

 

There is some thought that the positive cosmological constant is the result of the energy of the vacuum in quantum electrodynamics. The vacuum energy results in a negative pressure term, equivalent to a positive cosmological constant, in the stress-energy tensor. However, calculations of the value of the negative pressure over-predicts the observed cosmological constant by a factor of [math]10^{120}[/math], which is the largest over-prediction in the history of physics. In short, nobody understands what is going on. This is one of the major mysteries of current physics.

 

None of this has much to do with the question of the topology of the universe. That too is an open question, and one that is likely to stay open for a long time. The (spatial) universe could be a 3-sphere, it could be flat Euclidean space, it could be hyperbolic, it could be a flat 3-torus or it could be something else. Nobody knows.

[JustinW]

Yes I agree. I was basing my questions on the more popular models and understand that they are incomplete and unreliable until a new model comes out that can explain these things.

 

There is some thought that the positive cosmological constant is the result of the energy of the vacuum in quantum electrodynamics. The vacuum energy results in a negative pressure term, equivalent to a positive cosmological constant, in the stress-energy tensor. However, calculations of the value of the negative pressure over-predicts the observed cosmological constant by a factor of , which is the largest over-prediction in the history of physics. In short, nobody understands what is going on. This is one of the major mysteries of current physics.

Yes I've done a little reading on the subject. The theory couldn't be true just on the basic definition of how a vacuum works. When matter is removed from space, it creates a vacuum. The more matter that is removed the greater the vacuum. If space were expanding then the vacuum of space would grow equal to the rate of expansion.

 

And until further proof of expansion is known, I don't see how we can favor expansion over just plain movement. (via red shift)

Edited December 14, 2011 by JustinW