# Dark energy vs. gravity

If dark energy is everywhere around us, then why don't we get separated? For example why don't I get separated from the pen kept in front of me? Or take a similar example in free space. Is dark energy's power greater than gravitational power?

• Why would you think that dark energy would "separate" you from anything? – ACuriousMind Jul 15 '14 at 16:40
• I believe he is asking why dark energy doesn't dominate over gravity at short scales. – levitopher Jul 16 '14 at 1:16
• Possible duplicates: physics.stackexchange.com/q/2110/2451 and links therein. – Qmechanic Jul 16 '14 at 10:39
• Let's assume, for the moment, that space expansion did work at our scale and in the presence of gravity. It would take more than 19 years for the pen half a metre in front of you to move more than a few atoms' widths away from you. Space does not expand very fast – Jim Apr 22 '15 at 15:59

Dark energy is responsible for the acceleration of the universe at large scale, that is, it causes the second derivative of the cosmic scale factor $a(t)$ to be positive. But a smaller scales we found agglomerates of particles where the effect of the four forces (not only gravity) is much stronger that the repulsive effect of dark energy. A useful analogy which can help to understand what's going on is that of the raisin bread where a bread is expanding on the oven but the raisins on it (the agglomerates of particles) do not expand.

The density of Dark Energy is not very high. In a place with lots of matter, the attractive forces of gravity are greater than the repulsive forces of dark energy. In mostly matter empty space, the repulsive forces of dark energy are much larger than the attractive forces of gravity.

• Not to mention the MUCH stronger electromagnetic interactions we experience. Gravity may keep me from floating away from Earth, but electromagnetism prevents me from falling through it. – Kyle Oman Jul 15 '14 at 16:43
• The strength of dark energy also scales up with distance, no? The opposite is true of gravity, of course. – Nick Stauner Jul 15 '14 at 16:43
• @NickStauner I've never heard that, I don't think that's true. – jhobbie Jul 15 '14 at 16:44
• I've probably misunderstood Hubble's law then. Can't find a source that corroborates what I said now, so I think you're right, and I wasn't. – Nick Stauner Jul 15 '14 at 16:49
• @NickStauner The reason that things that are farther away are moving faster away from us is because they are farther away. In a certain amount of time, space will double in size. That means that a galaxy intially 10MPc will be at 20Mpc, and one at 1MPc will be at 2MPc. The distance between them and us now has doubled each, but gives the first galaxy a much larger recessional velocity because it has retreated farther. Does that make sense? – jhobbie Jul 15 '14 at 16:55

Gravity and dark energy would have to be one & the same, due to the fact that gravity is spacetime and space time is basically the mother board or rather the rawness or better, the naked form of the universe.

If einstein is correct about spacetime curvature than both are just different movements of the same entity, sort of like, how a river moves forward, all while bumping into stones, splitting them and emerging into larger aquatic bodies.It still remains the same water no matter what the direction and the pull of gravity is, similar to a river becoming stagnant as the water seeps into the rocks, its curving around.

So dark energy and spacetime may be the same river representing space with a liquid light quality or an invisible light that behaves like water as a whole.

• ... What? Gravity and dark energy don't have to be "one and the same." Why do you think that? – Asher Feb 2 '16 at 3:36
• I lost you after Gravity and dark energy. Consider breaking your paragraph up into sentences. – Bill Alsept Feb 2 '16 at 3:41