[goohle]

It looks like Big Shrink (BS) theory is easier to understand: we are shrinking, our rulers are shrinking, so cosmic distances are looking bigger in every direction. It explains why our Universe is flat and why we cannot find a Universe-big source of energy for expanding of the Universe.

[jjk166]

This doesn't make sense either - if I were shrinking and you were shrinking, then the distance between us would appear to be growing larger, but it's not. Gravitationally bound systems don't expand, only the galaxies themselves seem to be moving away from one another. Combined with no mechanism to explain the shrinking, nor any reason why the various other laws of physics don't seem to be affected and it doesn't seem any easier to understand at all.

[Beldin]

Just curious, since gravity works over infinite distances (as I understand things):

When do two masses stop being gravitationally bound? Is that when each mass's relative speed exceeds the escape velocity of the other mass?

No, that can't be right: they could still end up in orbit - obviously gravitationally bound.

[msk-lywenn]

But what energy is making us shrink?

[klyrs]

From the article:

> “The memory is nothing but the change in the gravitational potential,” said Thorne, “but it’s a relativistic gravitational potential.” The energy of a passing gravitational wave creates a change in the gravitational potential; that change in potential distorts space-time, even after the wave has passed.

Gravitational waves are that energy.

[contravariant]

Conservation of energy gets a bit screwy with these kinds of cosmic models. Partially because there isn't a single direction of 'time', but also because all kinds of energy gets stored in the fabric of space-time which can cancel out all kinds of things.

Not to mention that there's no reason to assume conservation of energy still holds if the laws of physics simply change over time (which would be the case in the simplest possible theory were all interaction distances simply shrink over time).