How our brains create time (Humans)

by David Turell , Saturday, April 30, 2022, 18:39 (719 days ago) @ David Turell

Ethan Siegal on time:

https://bigthink.com/starts-with-a-bang/does-time-exist-182965/?utm_source=mailchimp&am...

"Time is relative, not absolute. Time always marches forward, not backward, but we still lack an explanation for the arrow of time. Thermodynamically, the Universe has an arrow of time, which “flows” in the same direction as increasing entropy. And when we investigate the Universe on a fundamental level, it turns out that time may not be fundamental at all.

"But existence itself? It’s very, very difficult to take that property away from time and to still wind up with a Universe consistent with what we observe. Here’s why.

"When it comes to the question of existence, physics is very simple and straightforward about what it considers to be a satisfactory answer.

"Can you measure it?
Can you quantify it?
Can you define it in a mathematically self-consistent way?
Is it, itself, an observable quantity, and do other observables depend on it in an inextricable way?
If your answers to these questions are all in the affirmative, there’s no way out of it: you’ve got yourself a quantity that exists.

***

"Yes, you get different answers to the question of “How much time has passed?” or “When did this event occur?” or even “Which event happened first?” depending on where you are and how you’re moving, but no one is more “right” or “wrong” than anyone else. Instead, we just need to transform our idea of time — according to the laws of relativity — to match what someone at either a different location or moving at a different relative speed would conclude.

***

"In fact, almost all of the laws of physics — including motion, gravitation, electromagnetism, and even the strong nuclear force — are completely time-reversible. They are the same forward and backward in time, and you cannot discern, simply by watching a physical system unfold, which one is occurring.

***

"It will often happen that a neutron decays into a proton, an electron, and an anti-electron neutrino. But it never happens that a proton, an electron, and an anti-electron neutrino spontaneously react together to form a neutron. In fact, in a variety of ways, the weak interaction is the poster-child for time-asymmetric reactions in physics.

"The second way, however, is even more familiar to most of us. Every time you:

"scramble an egg,
drop a full glass of water onto the ground and watch it shatter,
or simply open the door between a hot room and a cold one,
you are creating a situation where there will be a thermodynamic arrow of time.

***

"We do not know what causes our perceived arrow of time. We always observe time to be flowing forward and not backward; we recognize the passage of time and are subject to the laws of physics moving forward in time, just as all physical objects and quantities are. But whether the entropy of your system remains constant, increases slowly, increases rapidly, or is even artificially decreased by inputting energy into it, the perceived arrow of time never ceases to flow nor reverses direction.

"While time is definitely real, it may or may not be fundamental. In our present way of looking at the Universe, we view something like entropy as a derived quantity and treat time as though it’s fundamental. However, mathematically, it is possible to treat entropy as though it’s a fundamental quantity, and then time behaves as though it can be an emergent quantity. We do not yet know enough about the Universe to comment much about the potential validity of this approach.

"Time is an integral part of the Universe, and the boundary between events that have been observed or measured to have a definitive outcome and those whose outcome has not yet been decided is the best way we have to define, precisely, what we mean by the moment of “now”. As esteemed physicist Lee Smolin put it in an exclusive interview with him:

“'in the Copenhagen version of quantum mechanics, there is a quantum world and there is a classical world, and a boundary between them: when things become definite. When things that are indefinite in the quantum world become definite. And what they’re trying to say is that is the fundamental thing that happens in nature, when things that are indefinite become definite. And that’s what “now” is. The moment now, the present moment, that all these people say is missing from science and missing from physics, that is the transition from indefinite to definite.”

"Time may or may not be fundamental, and our perceived arrow of time may or may not (my hunch is “not”) be related to the thermodynamic arrow of time. But the fact that we can measure, observe, and quantify it should put any doubts of its non-existence to rest."

Comment: We invent segments of time, but what we are doing is setting up arbitrary measurements of sequential events, based on our 24-hour day,