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Author Topic: How do we know that Dark Energy has negative gravity?  (Read 2765 times)

Offline Joe L. Ogan

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We are not sure that Dark Energy even exists but it is stated that Dark Energy has negative gravity.  How can we prove this?  Thanks for comments.  Joe L. Ogan


 

Offline PhysBang

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How do we know that Dark Energy has negative gravity?
« Reply #1 on: 30/12/2009 01:32:42 »
We know it does this because we can measure its effect. For example, we can see that the recession of distant galaxies is speeding up.
 

Offline Joe L. Ogan

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How do we know that Dark Energy has negative gravity?
« Reply #2 on: 30/12/2009 02:05:19 »
We know it does this because we can measure its effect. For example, we can see that the recession of distant galaxies is speeding up.

Are we sure that Dark Energy is doing this?  We do not even know if Dark Energy exists!  Does it have negative gravity or positive energy.  That is if it even exists?  Thanks for comments.  Joe L. Ogan
 

Offline Joe L. Ogan

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How do we know that Dark Energy has negative gravity?
« Reply #3 on: 30/12/2009 22:37:07 »
We know it does this because we can measure its effect. For example, we can see that the recession of distant galaxies is speeding up.

Does Dark Energy have any matter?  I thought it was necessary for something to have matter in order to have gravity.  Does this not apply to Negative Gravity?  Thanks for comments.  Joe L. Ogan
 

Offline PhysBang

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How do we know that Dark Energy has negative gravity?
« Reply #4 on: 30/12/2009 22:52:34 »
Are we sure that Dark Energy is doing this?  We do not even know if Dark Energy exists!  Does it have negative gravity or positive energy.  That is if it even exists?  Thanks for comments.  Joe L. Ogan
Well, we know that something exists with the properties of dark energy.

There is no such thing as negative gravity and positive gravity. There is only gravity. Roughly, if we add something called the cosmological constant term to general relativity, this term can act to either attract masses to other masses or it can act to repel masses from other masses, depending on the positive or negative value of the term. This term can be used to represent a form of vacuum energy that we call dark energy if the term is positive. Currently there are different ways to measure the value of this term and get roughly the same positive value.
 

Offline Joe L. Ogan

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How do we know that Dark Energy has negative gravity?
« Reply #5 on: 30/12/2009 22:59:47 »
Are we sure that Dark Energy is doing this?  We do not even know if Dark Energy exists!  Does it have negative gravity or positive energy.  That is if it even exists?  Thanks for comments.  Joe L. Ogan
Well, we know that something exists with the properties of dark energy.

There is no such thing as negative gravity and positive gravity. There is only gravity. Roughly, if we add something called the cosmological constant term to general relativity, this term can act to either attract masses to other masses or it can act to repel masses from other masses, depending on the positive or negative value of the term. This term can be used to represent a form of vacuum energy that we call dark energy if the term is positive. Currently there are different ways to measure the value of this term and get roughly the same positive value.

Does something have to have matter to have gravity?  Does Dark Energy have matter?  Thanks for comments.  Joe L. Ogan
 

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How do we know that Dark Energy has negative gravity?
« Reply #5 on: 30/12/2009 22:59:47 »

 

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