What is time? Sean Carroll explains. (The philosophical view favored by physics)

[C C]

https://youtu.be/MAScJvxCy2Y

VIDEO EXCERPTS: In lecture one we discussed this analogy of thinking about the universe as a movie reel or a film strip: A series of frames, a series of moments. ... The whole movie reel defines what we think of as the universe. It's this four-dimensional thing -- both space and time. And I have to caution that when we use that analogy, it's very tempting to wonder whether or not like a film strip, moments of time are discrete.

As far as we know, nothing in physics tells us that time is discrete. As far as we can tell, time is perfectly smooth and continuous.

People sometimes wonder whether or not a future reconciliation between quantum mechanics -- the theory that happens at the very small scales -- and Einstein's theory of gravity may someday tell us that time really is discrete.

[...] But as far as we know, that's not true. Their best understanding right now ... has time being absolutely smooth and continuous. That's not to say that we will not get a better understanding of it in the future. But right now, I'm not trying to use the filmstrip analogy to say that time comes in discrete packets...

[...] Looking at this four-dimensional block universe to treat the past present and future on an equal footing, this seems to be the right way of looking at things as suggested by the current laws of physics.

I should be honest in saying that it's a controversial point of view. Many philosophical stances are controversial. There are certainly philosophers out there who don't believe in eternalism. To me it seems to be the logical consequence of the physicist's way of looking at the universe. But it should be kept in mind that there are other ways to do it.

What does it mean if it is true that the past, present, and future are equally real? We certainly think of them very differently. We treat the future very differently from the past.

Another way of thinking about our sort of folk traditional, everyday way of thinking about the universe is the growing block universe model. I said that presentism treats the present moment as real, and the past and future are not real. So a slight twist on this idea is to treat the present and the past as real, but not the future.

[...] So the past is fixed, it's in the books, it's real. [...] Whereas the future is up for grabs. So maybe we should treat them very, very differently. This seems natural to us as human beings, but it has no reflection in the ultimate laws of physics. It is not something that we get any warrant for from our best understanding of the universe.

[...] It's the arrow of time that gives us the impression that time passes, that time flows, that we progress through different moments. So from that perspective we understand that it's not that the past is more real than the future, it's that we know more about the past. Our memories access moments in the past, and when I say memories, I don't just mean the actual memories in our brains. I mean any record, any fossil, anything that we can look and believe it gives us reliable knowledge about the past.

We live in a world where memories exist, where there are history books. There are no history books written about the future. That's the difference between them, which can ultimately be traced to the arrow of time.

So it's not that the past and the future don't exist, it's that we have different access to them. We were in the past, and the memories of that past are still reflected in the present day.

[...] All moments of time seem to be real, but some we understand better than others. That's something we're going to be developing when we get to the reflection of the arrow of time and how we think and about how our brain processes information. So all this is a little bit philosophical, as we promised. So let's get more concrete about how it plays out in the everyday world...

What Is Time? Professor Sean Carroll Explains. ... https://youtu.be/MAScJvxCy2Y
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https://www.youtube-nocookie.com/embed/MAScJvxCy2Y

[Magical Realist]

It might be more accurate to say that instead of experiencing time as this continuously flowing transition from before to after that we are actually strobing the events that are happening around us. It's like those strobe lights we played with when we were kids. You throw a pillow in the air and you see a succession of freeze frames of the pillow flying thru space. But that of course is only an illusion. Likewise our consciousness is always strobing at a certain and perhaps variable frequency. We experience the events around us as discrete moments like microseconds, one causing the next in perfect lawlike manner. But that is just our subjective perspective. In reality there is just the continuous flowing of events, the smooth flux of happening itself like that of a river. The whole domain of past, present, and future really fusing together into one streaming reality. A song, a story, a film, a life.

[C C]

It might be more accurate to say that instead of experiencing time as this continuously flowing transition from before to after that we are actually strobing the events that are happening around us. It's like those strobe lights we played with when we were kids. You throw a pillow in the air and you see a succession of freeze frames of the pillow flying thru space. But that of course is only an illusion. Likewise our consciousness is always strobing at a certain and perhaps variable frequency. We experience the events around us as discrete moments like microseconds, one causing the next in perfect lawlike manner. But that is just our subjective perspective. In reality there is just the continuous flowing of events, the smooth flux of happening itself like that of a river. The whole domain of past, present, and future really fusing together into one streaming reality. A song, a story, a film, a life.

And if there really were objective or mind-independent discrete units of time (instead of a continuum), then they would have to accommodate changes at the subatomic level, which can even occur in the range of rontoseconds (one octillionth of a second).

Since snapshots of human consciousness (our cognitive states) are indeed measured in milliseconds (i.e., slow in comparison), a single one of our time intervals would have to contradictorily extend over an incredible multitude of those (speculative) objective global units. Meaning that the latter would have to co-exist with each other (like those frames of a movie). Or else somehow our "subjective nows" would be more fundamental -- always surviving longer than a single, ludicrously brief state of the universe that existed "out there". An inversion which would make no sense in the context of physicalism.

Thus, Einstein's work isn't even necessary to infer that all the different states (figurative 4D slices of the cosmos) endure -- that is, if one desires to hang on to materialism and not succumb to a heavy dose of anthropocentrism. Immaterialism, solipsism, "this is a dream", etc -- whatever it would take to enable a reality to revolve around the human experience rate of change, instead of a (fancifully imagined) objective one.

[Magical Realist]

Reinstalling the idea of a continuous flow of time right there at the primal intracerebral lapse has the advantage of freeing us from an exclusively compositional or quantitative kind of causality and logic. Instead of the bottom up accumulation of moments resulting in a higher level whole state, we have the continuity of moments qualitatively changing and transforming into new states. The part and the whole are no longer discrete from each other but intertwined within a dynamic transmuting flux. The whole universe sings itself thru our scintillating neurons, resonating forth the colorful music that holds everything together.