I How is the arrow of time defined?

[PeterDonis]

A white hole model that fits cosmological observations would have to be the time reverse of a star collapsing to form a black hole.

And we would have to be inside the non-vacuum region occupied by the exploding matter, yes.

we cannot rule out the possibility that the universe is a very large white hole

Not just based on the observation that the universe is expanding and that its matter density appears to be uniform on large scales, no. But the article you quote does not take into account the fact that the expansion is accelerating (it was written in 1997, when that part of our current best-fit cosmological model was still not fully established). There is no way to get accelerating expansion in a white hole model; the expansion in such a model can only decelerate.

 

[Stephen Tashi]

Perhaps the processes that implement our consciousness only have a "forward" direction in time, so we think time goes in that direction because our processes of thought go that way.

As far as we can tell, this isn't the case; the processes that implement our consciousness do not involve any of the particular aspects of the weak interaction that are known to be time asymmetric.

What is the interpretation of "As far as we can tell"? I think you mean that as far as we can imagine a mathematical model of physical processes that implement consciousness, we imagine them to be time symmetric. On the other hand "as far a we can tell" from direct experience, we do distinguish between a past and a future.

 

[PeterDonis]

I think you mean that as far as we can imagine a mathematical model of physical processes that implement consciousness

No, I mean as far as we can tell about the actual physical processes that go on in our brains, they don't involve any of the aspects of weak interactions that are known to be time asymmetric. It's all basically electromagnetism, which is known to be time symmetric.

"as far a we can tell" from direct experience, we do distinguish between a past and a future.

Yes, but that doesn't tell us whether the underlying physical laws are time asymmetric. It just tells us that something is time asymmetric. That something could just as well be the initial conditions.