What on earth is 'mass has a constant volume' supposed to mean?
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Shambolic - keeping it complex analytic

I, too, hate the rubber sheet analogy because it often confuses students into thinking that space is some kind of substance or something! What Einstein said is that the geometry of space-time is curved around objects with mass. That curvature of space-time alters the paths of objects moving through spaces, causing them to have curved trajectories. It really has nothing at all to do with rubber sheets - just geometry.

BTW, take what you read on that "space gravity" page that was linked to on the first page of this thread with a grain of salt. The guy that wrote it is a psuedoscientist, although he does get some stuff right and some stuff wrong.
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"Science is the most precious thing we have."
-Albert Einstein

Here is a nice little link that has a quick discussion:

http://members.aol.com/RELAPHYZIX/GRAPHINGGRAVITY.html

Check it out.


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BENFOW
CLICK HERE TO VISIT THE POOR MAN'S ASTRO WEBSITE

Here are some references to "electro-gravity", which are fun, though I have no idea if they're any good or not:

http://rognerud.com/physics/html/rotating.html
http://jnaudin.free.fr/html/electrog.htm
http://jnaudin.free.fr/html/lifters.htm
http://alephzero.gmxhome.de/antigrav/

Have fun!

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I have formally 'resigned' (tactical withdraw) from the Space-Talk boards; mine were many questions, ideas, but no real answers. Thanks. 04/10/04.

Disclaimer: Please note the ideas expressed here by me are cutting edge theory, very speculative in nature, and not physics as it is being currently taught. Caveat lector.

Copernicus 2 -

Take that stuff with a grain of salt. "Electro-gravity"? Sounds kinda fishy to me...
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"Science is the most precious thing we have."
-Albert Einstein

gravity is a psuedo-force much in the same way that centrifugal force is a psuedo-force. it is caused by the temporal inertia of mass (its tendancy to remain at rest in a given moment in time) being accelerated through space-time.
the acceleration is provided by the accelerated expansion of the universe. as a body of mass exists in space, the 'outward' expansion of space tries to push the body of mass through time as well. as space expands, it encounters resistance from the temporal inertia of the body of mass resulting in a curvature of space-time around it.
other bodies of mass are not actually 'pulled' towards another body of mass, so much as space-time is expanding around them. 'realatively' speaking, the distance between the bodies of mass will become less... in a sense, it is the function of a percentage of the realative distances between the two bodies of mass as compared to the mean volume of space at a given moment in time. (of course, other factors such as total mass and velocity and trajectory influence the behaviours of the various bodies of mass which interact with each other.)


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an open mind with a closed fist

Just what is said in the following link:

http://members.aol.com/RELAPHYZIX/GRAPHINGGRAVITY.html

but, of course, before the recent discovery of the acceleration of the Universe's expansion, what was the explanation offered by allthe pseudo-experts??
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BENFOW
CLICK HERE TO VISIT THE POOR MAN'S ASTRO WEBSITE

well I'll be shooker-shnooked! I had no idea that anyone else had come up with this theory before me! I don't know whether to be humbled or to feel proud that my mind is on par with some of the most noteable physicists out there!

it would seem to me that explanations prior to the discovery of the accelerated expansion of the universe are now obsolete and irrelevant... unless you are interested in the history of the progress of modern science, of course.
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an open mind with a closed fist

I don't know about 'the most noteable physicists out there'; more like 'some guy with a bit of maths know-how, an opinion, and a website'.
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Shambolic - keeping it complex analytic

its a new subject, but we are learing things about anti-gravity.

The universe wasn't slowing down; it was speeding up! "This seemed to imply," he says, "that some force is acting against gravity."


http://www.time.com/time/innovators/science/profile_riess.html

http://nedwww.ipac.caltech.edu/level5/March01/Dark/Dark.html


On May 9th two teams of scientists issued a "midterm report" on the expansion rate of the universe, one of the long-term Key Projects being undertaken by the Hubble Space Telescope. Both groups use HST to pick out Cepheid variable stars in distant galaxies. These stars pulsate at rates related to their brightness, so they serve as "standard candles" that allow distances to be measured accurately.

It's then possible to calculate how fast the universe is flying apart. One team, led by Wendy Freedman, finds that this controversial Hubble "constant" lies between 68 and 78 kilometers per second per megaparsec. That value, combined with the usual assumption about the large-scale density of matter, implies that the universe is only 8 or 9 billion years old. The second team, led by Allan Sandage, studied Cepheids only in galaxies in which Type Ia supernovae have been seen. That enables them to gauge other supernova-hosting galaxies hundreds of millions of light-years away. Their Hubble value is only 57.
km/sec/Mpc, implying an age of about 12 billion years.

http://physicsweb.org/article/news/3/5/12/1

So can the universe be younger than the stars it contains? No, but the results may mean that ours is a low-density universe whose expansion is only gradually slowed by gravity. Or Einstein's infamous "cosmological constant," which imbues empty space with antigravity-like properties, also might be involved.






For w = -1 we have Einstein's cosmological constant with = 8 G / c2 (cosmological vacuum with w = -1) and the gravitating mass is M = -8 r3 / 3. Thus the generalized Newtonian potential leads to a gravitational interaction acceleration

which is expected to dominate at distances larger than



(8)

where 1 is the mass within a sphere of radius rc in units of solar masses M = 2 × 1030 kg and 52 is the cosmological constant in units of 10-52 m-2



(6)

This generalized force includes a repulsive term
http://hubble.nasa.gov/project-news/

http://www.geocities.com/anti_gravity/exper.html