Something struck me the other day...

[sorgoth]

I was thinking about the universe expanding at an increasing rate and the fact that gravity DOES something, but seems to use no energy, and how those two concepts didn't make any sense to me, when I started thinking about something...


What if gravity is getting weaker? What if there's something akin to a gravitational half-life? This theory would require gravitons to exist, but it seems to go with the universe expanding at an increasing rate theory. (There's less and less holding the universe back).


Now, this is more a hypothesis than a theory, I know. Comments?

 

[geni]

Gravity does use energy. It just used it in a negative way. I way to get you mind round this idear is that you need energy to move to objects apart but once you have moved them apart they still have the energy you put in in the form of gravitational potential energy

 

[espritch]

I’ve been playing around with a notion related to this. It’s a two part idea. The first part relates to dark energy. According to general relativity, gravity is a curvature of spacetime caused by matter. Now suppose the natural state of spacetime is flat. You could say the reason the universe is expanding is that spacetime is just trying to return to it’s natural state (i.e. it resists being curved and that resistance is what we call dark energy).

The second part assumes that gravity is not linear. That is to say, the gravitational effect of X amount of matter and Y amount of matter is not X+Y but rather X+Y+Z where Z is a function of the total amount of matter. This function represents a curve that is very small for small amounts of matter (the way relativity effects are tiny for low velocities); slight enough to escape notice in lab experiments. But it becomes significant for large conglomerations of matter like galaxies (the way relativistic effects become significant as you approach light speed), this might mean that dark matter doesn’t really exist and observations normally attributed to it (such as the excessive rotation rate of galaxies) are actually a result of the non linear behavior of gravity.

On a larger scale, as the universe expands, there is a net reduction in the overall density of matter in any given region of space which would reduce the Z component of gravity for that region. The result would be an increase in the rate of expansion over time.

Of course this is pure speculation on my part, but I thought I would just toss it out there for consideration.

 

[Ziggurat]

The second part assumes that gravity is not linear.
...
Of course this is pure speculation on my part, but I thought I would just toss it out there for consideration.

I think your first part is mostly just wild speculation, but I did want to interject that in general relativity, gravity is explicitly nonlinear - that's already a central aspect of the theory.

 

[clusterm2]

Of course this is pure speculation on my part, but I thought I would just toss it out there for consideration. [/B]

Is there anything other than speculation in cosmology, where computations are based on a series of nested assumptions (most of which are contentious)
Toss away, it's as believable as any other current theory.

 

[The Don]

If gravity were getting weaker there would be a profound effect on the structure of the solar system and indeed on the gravitational force as experienced on earth.

The structure of fossils, the strength of the bones and so forth is consistent with the current value of the gravitational constant. If gravity does have a half life it will be exceedingly long.

 

[neutrino_cannon]

Something struck me the other day...

Did it hurt?


If gravity did have a half-life, I know that it would make black holes even wierder than they already are.

Since that can't happen, your hypothesis is false.

I can't imagine there's any compelling evidence for this, and I would posit quite abit against it. What would happen to orbits if gravity got weaker and weaker? Where would our solar system be?

Interesting thought though. Reminds me of a theory that C might not be constant if the temperature is high enough, and creationist dribble about radioactive decay not being constant, thus invalidating radioisotope dating methods.