I simply cannot wrap my head around this, any more than I can the Twin Paradox. Maybe some physics guy here can explain it to us.

This all sounds like hand-waving and navel-gazing, smoke and mirrors from the physicists, but they can make machines and predict events that are not interpretable by classical physics. They are on to something, and I’m afraid we’ve been left out.

I don’t know, nobody does. The physicists make these weird assumptions that meet the symmetries of their mathematics and their observations and it helps them make valid predictions about atomic particles and gravity waves and multiple universes. What that all has to do with the universe we actually interact with, the chemical, biological, psychological, cultural, historical universe we actually live in, I don’t know. Yeah, yeah, I know they are intimately connected, but until we know how, it is all meaningless to us.

Maybe it has to do with dimensions. Have you ever read Abbott’s “Flatland”? The two dimensional creatures of that world are smart, and they are observant, and they are good mathematicians, but since they can’t see the third dimension, and since they can only think of it mathematically, they just can’t grasp the world around them, even when a helpful 3-d human tries to explain it all to them. The Flatlanders can see the shadows of 3D objects projected into their space, but they cannot see the objects themselves. Look up “Tesseract”. Its the 3D shadow of a 4D
hypercube, projected into our 3D space.

https://en.wikipedia.org/wiki/Tesseract

Maybe our inability to see some higher-level dimension makes it impossible for us to grasp the true nature of reality. I’ve always suspected there is at least one other dimension, perhaps many more, but I haven’t any clue as to what they might be.

I’m just speculating, but I think the next dimension is “Complexity”. An event in space time can be described as a manifold in (x, y, z, ict, C). We have just started to explore this dimension using fractal geometry.

But I’m just speculating. Maybe our brains simply cannot understand the nature of reality, even if we are capable of partially describing it using abstract mathematics.

Even if we can agree on why a “now” exists, can we presume that there’s a universal now even for people who occupy the same frame of reference?

So even though we’re aware that the entire universe exists, in terms purely of space, we for the most part perceive ourselves as existing only within the confines of our current surroundings–which represent, of course, only the tiniest part of the whole. I can certainly imagine myself anywhere else in the universe, but it’s abstract and unreal. In the end, I am where I am.

The same with time: our surrounding “area” is the present–past and future are beyond our temporal horizon. Our senses are capable of perceiving–and perhaps our brain capable of interpreting–only our tiny local snippet of spacetime.

OK, so that might help explain the notion of “the present.” What then differentiates the past from the future? For example, why can we remember the past, but not the future?

Einstein’s description (and it may not be the last word either) is not directly accessible to our senses, we certainly evolved to function in that universe, but we did not evolve the ability to understand it, or even perceive it.

Think of it this way. When we throw a baseball, we have complete control of its flight with our muscles and bones, balance of our bodies, and with the information received through our eyes and sense of touch and balance. But the motion of the ball involves things like gravitational forces, air resistance, things we weren’t even aware of when we evolved the ability to throw stones and weapons. We simply don’t need to know about the Laws of Motion or the mechanics of fluids
to hit a rabbit, or a catcher’s mitt. But we nonetheless managed to evolve the means of doing so fairly accurately, and, what’s much more important, we also evolved the ability to LEARN how to throw different things with sufficient accuracy for our own purposes: hand grenades, life preservers, Frisbees, pub darts, all without any knowledge of Isaac Newton or Albert Einstein.

In fact, a mastery of classical dynamics and kinematics is actually quite useless when what we are trying to do is keep the ball out of the strike zone, but as close to it as possible, while simultaneously making it as hard as we can for the batter to predict its motion and hit it. Incidentally, he is using those same human skills we rely on to throw in order to swing his bat and get a hit. And that human reality is totally inaccessible to either Einstein or Newton. They knew nothing about baseball. They didn’t have to.

There is a real world, and the perceptual world we live in. Both are equally valid, one is actually part of the other, but only one is experienced by us directly, and accessible to our actions. Try not to think of which world is more real, or more important. That is the wrong way to think about it. In fact, it can be quite misleading.

There is really only one world, we just can’t see all of its parts at once. There may be a totality and continuity of space-time, just as there is to the surface of the earth, but each of us walks and sees a different landscape.