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Is time a fundamental part of reality? A quiet revolution in physics suggests not (theconversation.com)

submitted 2 days ago by Powderhorn@beehaw.org to c/science@beehaw.org

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Time feels like the most basic feature of reality. Seconds tick, days pass and everything from planetary motion to human memory seems to unfold along a single, irreversible direction. We are born and we die, in exactly that order. We plan our lives around time, measure it obsessively and experience it as an unbroken flow from past to future. It feels so obvious that time moves forward that questioning it can seem almost pointless.

And yet, for more than a century, physics has struggled to say what time actually is. This struggle is not philosophical nitpicking. It sits at the heart of some of the deepest problems in science.

Modern physics relies on different, but equally important, frameworks. One is Albert Einstein’s theory of general relativity, which describes the gravity and motion of large objects such as planets. Another is quantum mechanics, which rules the microcosmos of atoms and particles. And on an even larger scale, the standard model of cosmology describes the birth and evolution of the universe as a whole. All rely on time, yet they treat it in incompatible ways.

When physicists try to combine these theories into a single framework, time often behaves in unexpected and troubling ways. Sometimes it stretches. Sometimes it slows. Sometimes it disappears entirely.

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[–] irotsoma@piefed.blahaj.zone 3 points 2 days ago (1 children)

It also works much like space, only a single dimension. And similar to space, the distance between two points on a line can change if the line is stretched without affecting the distances of things around it necessarily, the distance between to places in time can change locally through time dilation.

So take a piece of elastic and an piece of paper. Draw a line on the elastic and an equal length line on the paper. Take two small windup toys or some other thing that can move in a straight line at a steady pace and that both move at the same speed. And put one on the paper and one on the elastic. Now imagine that the toys or whatever can only look down, directly at the line and points (i.e. they're one dimensional).

Normally, both will reach the end of their lines at the same time. But stretch the elastic and run them again and one reaches the end faster than the other. There's been no break in the line and the points weren't changed and they're both still moving the same speed, but the space that the elastic one exists in has been stretched or "bent".

Not the best analogy exactly for understanding the concept itself, but understanding that there's often an underlying thing that usually remains unobserved or in the case of time dilation or bending 3D space, something that is not observable by humans (or the toys) is what to take away. What we perceive is only a small part of what exists. We can only see the effects those things have on space and time to prove that they must exist.

[–] remington@beehaw.org 1 points 2 days ago

That’s interesting. I like that analogy.