Why doesn't Dark Energy effect things on a smaller scale then galaxies?

Answer 1

We don't know.

"Dark energy" and "dark matter" are more-or-less euphemisms for "we have no idea what the heck is going on here."

In the case of dark matter, the "here" has to do with the rotation of galaxies. If Newton's Law of Universal Gravitation is even approximately correct on a galactic scale, then galaxies don't rotate properly. We can fix this problem in one of two ways: we can assume there's a lot of mass that's hidden from us and only interacts via gravity (and, possibly, via the weak force, which turns out to only act over such tiny distances that we can completely ignore it for something the size of a galaxy ... or for that matter, the size of a grain of sand), or we can assume Newton's equations are just the small-scale limit, and that a different law applies for objects the size of galaxies. Both approaches have been tried; both are consistent with observed data, but neither has been absolutely proven correct.

In the case of dark energy, "here" has to do with the cosmological constant. When Einstein was attempting to work out his equations about how the universe behaves, he found it necessary to add an arbitrary parameter in order to get the equation to agree with observations. Actually, the model would have been consistent with what was then known about the universe if you assumed it was expanding. Einstein didn't like that for philosophical reasons, and put in the constant.

We now know the universe is expanding, whether we like it or not, but we also know more about how it's expanding, and it turns out that having a non-zero value for the cosmological constant makes the model work better. Scientists don't like inserting random parameters into equations without at least trying to explain where they come from, and "dark energy" is one attempt to explain the fact that the cosmological constant does not appear to be zero.

The reason it "doesn't affect things on a smaller scale than galaxies" ... according to theory, it does. It's just such a very, very tiny effect that on the small scale ... and by "small scale", I mean anything not mind-bogglingly huge, not just galaxy-sized or ever galaxy cluster sized but more like "the spacing between superclusters" sized ... then the effects are utterly indetectable against the background of gravity and electromagnetic forces.

Answer2:

Dark Energy does effect things smaller than galaxies!

Dark Energy effects things on every scale from Cosmos to atom. Dark Energy is involved in every spec of mass that moves, it is the product of Momentum and the speed of light, cP. Momentum is everywhere from the neutrino to the galaxies. Momentum energy, Dark Energy is everywhere there is Momentum.

Einstein's original conception was working on a stationary cosmos involving galaxies.. His mathematics did not show the stationary condition, so he added the Cosmological Constant. This was the correct idea. Einstein was looking for a centrifugal force to counter the centripetal force of gravity. Others assumed the equations were correct and the cosmos was dynamic either expanding OR contracting. The Big bang Theory and The red shift data was combined to conclude that the cosmos is expanding.

The more correct theory i call Quaternion Physics. The cosmos is not expanding and the Dark Energy is the source of the centrifugal force to bring about Stationary. The Dark Energy is the Momentum Energy, cP where P =mV, the Momentum vector. The Momentum is everywhere large and small sizes. The Dark Energy cP is also everywhere and large an small. It can be seen that Dark Energy cP = mvc is larger than "regular' energy mvv.

The centrifugal force comes from the Divergence of the vector energy

DEL.cP = -cp/r cos(P). The centripetal force is vp/r = mv2/r, the balance of these two forces give the Continuity Condition and the derivation of the red shift;

vp/r=cp/r cos(P) gives v/c = cos(P) the source of the red shift.

Thus the red shift is everywhere orbits are stable and indicate the Continuity Condition (the scalar forces summing to zero) and the Fermion Condition.

The Quaternion Physics answers the observations without ghost energy and matter. The Gravitational Energy is W= -mGm/r + cmV= -vh'/r + cP where the scalar/Boson energy is -mGM/r = -vh'/r and the vector/Fermion energy is cmV=cP the Momentum energy is the so-called "Dark Energy", Dark Energy is everywhere from the atom to the Cosmos; e.g. W = -vh'/r + cP where the electrons and Photons have the Momentum energy, cP.

*h'=h/2pi.

Answer 2

Dark energy is thought to be a property of space itself, causing the universe's expansion to accelerate. On smaller scales, such as within galaxies or solar systems, other forces like gravity dominate and prevent the effects of dark energy from being noticeable. Additionally, the amount of dark energy per unit volume is very small, which also contributes to its negligible impact on smaller scales.