General Question

krrazypassions's avatar

Can this be the explanation for dark energy?

Asked by krrazypassions (1332 points ) June 19th, 2011

Gravity is a long-range force. However, we assume it to act over infinite distances. All other forces are short-range and do not act beyond a certain range.

Maybe there is a limit to the distance upto which the gravitational force acts. Gravity stops acting after the distant galaxies have moved beyond a certain distance from each other, after which the galaxies continue to move away from each other, unrestricted due to the absence of a gravitational pull.

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10 Answers

ragingloli's avatar

Not really, because that does not explain the fact that the expansion of the universe is accelerating.

krrazypassions's avatar

@ragingloli haha.. i know.. what i said until now would only cause all distant galaxies to move apart at constant velocities- there would be no acceleration- unless you have the property of gravity to become repulsive beyond that range.

filmfann's avatar

@ragingloli What if the expansion of the universe isn’t accelerating? What if we are slowing down? That would cause our perception of time to be different, and our perception of the universe would speed up.
Probably a novice question, but I can take the hate.

krrazypassions's avatar

@filmfann It was discovered in the year 1997 that the expansion of the universe in accelerating, and since then more and more evidence has pointed out to the same fact. The factor for this acceleration was termed as dark energy.. this is how dark energy was ‘discovered’.

two teams won the prize for this discovery
paper by team 1
paper by team 2

And my question is about the factor causing this acceleration. Is it some unknown dark energy or is it rather some unknown property of the gravity?

Qingu's avatar

@krrazypassions, gravity works over distances via an inverse square law. This has been known since Newton.

What you’re proposing is that, at some arbitrary point, the inverse square law just stops applying. There are several problems with this idea.

1. There’s absolutely no evidence for it.
2. It’s not “elegant”—it creates more questions than it answers. What’s the source of the arbitrary monkey wrench in the inverse square law?

ragingloli's avatar

It is my understanding that it has been observed that in a vacuum, virtual particles pop in and out of existence constantly. This creates pressure, forcing the galaxies apart.

Qingu's avatar

Also, it’s not true that other forces “don’t act beyond a certain range.” It’s just that their action is infinitesmally small. Also, electromagnetism (unlike gravity) has two charges—so it can attract or repel. That’s why the sun doesn’t electromagnetically attract the earth. It’s not because electromagnetism doesn’t work over that distance; it’s because the sun’s and the earth’s positive and negative charges are about equal, so they cancel each other out.

Qingu's avatar

@ragingloli, I’m not sure that’s true… though it might be. But if it is true, it’s actually just question-begging. Since the reason there are virtual particles in a vacuum is because there is vacuum energy. So the question then becomes “what is the source of all this vacuum energy that the virtual particles are borrowing?”

krrazypassions's avatar

as Nassim Haramein puts it, “If the universe is expanding, something must be contracting?” based on the law “Every action has equal and opposite reaction”

mattbrowne's avatar

Maybe technicolor theory might explain not only to the nature of dark matter, but also dark energy. More research needed here.

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