[Serious] Is the Past Real?

[polymath257]

I would disagree with that. The brain takes time to process the information from the senses. In fact, it can take fairly substantial fractions of a second to do so. So, the actual experience is always delayed from even the sensory event, let alone the event being sensed.

In the case of, say, a nuclear event at the site of an individual, it would be likely that no experience would be had at all since the vaporization of the body would happen much faster than the nerve signals and the brain processing. A nuke a kilometer away  would be a different matter, depending on the size and speed of the fireball.

Yes, I do agree that parsing out what constitutes the present subjectively from within the universe has value.  I am curious about time at the cosmic level. Does the universe, as a whole have multiple states? If space-time is entirely within the universe, then it would seem it could not have multiple states or change.

I don't see why not. First, a probability distribution that is different in different time slices would allow, even require 'change through time'.

The notion of 'time at the cosmic level' is problematic in relativity and particularly so in a curved spacetime. You could define the local time as that experienced by a comoving observer, but there is no guarantee that generalizes globally.