So the universe's expansion is accelerating -- this is my take....

Constant acceleration requires a constant net applied force.

F = m * a

Therefore acceleration of an object will be directly related to the force applied to it.

A car accelerating is not an example of constant acceleration. When you step on the gas peddle you are supplying a constant amount of fuel (energy) to the engine. A constant increase in kinetic energy results.

KE = 0.5 * m * v^2

Therefore a car's speed will increase with the square root of the fuel supplied to the engine. Constant acceleration would require the speed to increase at the same rate always.

a = v / t

Therefore a car does not accelerate at a constant rate. But apparently the universe does! So if we substitute acceleration into the kinetic energy we get this:

KE = 0.5 * m * (a * t)^2

The kinetic energy of galaxies that are flying away from each other faster and faster has to increase with the square of time passed (parabolic with time).

Speculation - Galactic Solar Sails

Gravity pulls matter together and generates heat, e.g. cores of stars and planets. The heat escapes, and impinges on other planets and stars, transferring momentum and pushing them away. The giant size of galaxies might make them act like sails, so even though this effect might not tear solar systems apart, it might act on structures as large and gossamer as an entire galaxy.

Opinions?