Be the first pioneers to continue the Astronomy Discussions at our new Astronomy meeting place...
The Space and Astronomy Agora
|Lets Make A Deal, You Stay Out Of The Forums I've Been Visiting And I'll Stay Out Of The Forums You've Been Visiting.
Forum List | Follow Ups | Post Message | Back to Thread Topics | In Response To
Posted by Zephram Cochrane/">Zephram Cochrane on February 16, 2000 18:44:00 UTC
: : : Yabbut, a vacuum is an extreme case of a decompressed mass. Vacuums are not sources of anti-gravity.
: What about the gravitational field due to vacuum energy? Theoretically it acts as a source of gravity (i.e. cosmilogical constant).
: : What you really need is negative mass-energy, negative pressures or negative stress-energy-momentum tensors (happy with that pmb).
: : I found the two terms "energy-momentum tensor" and "stress-energy tensor" confusing since they refer to the same thing.
: In general - I'm happy if I'm clear.
: : This has never been observed in real life.
: What about the Casimir effect or the new experimental evidence of inflation and the accelerating expantion of the universe?
: : In physics every force (but gravity) has an equal but opposite.
: Do you mean by this that it has never been directly observed or is not allowed/predicted within general relativity?
: There is something that is very important in cosmology nowadays. It's known as a vacuum domain wall. They may have existed in the early universe. These objects are like walls but they repell matter rather than attact matter. A cosmic string neither repells nor attracts objects (i.e. gravitational force = 0) but it does alter the space around it making it non-Euclidean. However for straight cosmic strings the spacetime is flat. Also the spacetime near a vacuum domain wall is flat, yet there is a gravitational field.
Unless otherwise specified, web site content Copyright 1994-2020 John Huggins All Rights Reserved
Forum posts are Copyright their authors as specified in the heading above the post.
"dbHTML," "AstroGuide," "ASTRONOMY.NET" & "VA.NET"
are trademarks of John Huggins