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The closer we look at time, the stranger it gets

sciencefocus.com

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Re: The closer we look at time, the stranger it gets

#61

Post by sigmoid10 »

My_Name wrote: post #55

They nearly have it in the article but don't take the next step, which is to realise that time is gravity. We are falling towards the future at the speed of causality. You can slow your experience of that by travelling really fast, or by being near something with a large gravity. Quantum particles can simply ignore gravity and time while we are forced to feel their effects due to our size, like a mote of dust can ign…

Well, almost. Because these usual descriptions you give here are approximations. Yes, to the first order, gravity is expressed as the effect on time in general relativity. So you could describe how planets move simply by calculating how they move differently through time. But in the full picture, the way you move through space or near strong gravitational fields also influences your experience of space itself. So the ultimate realization is that gravity is space and time. Or spacetime. Basically exactly what the article says when it references general relativity. And it holds as well for quantum particles. They experience spacetime just as well as we do. The ultimate question is, does spacetime itself also come quantized when you look close enough? This is the true head banging one that noone knows.

Re: The closer we look at time, the stranger it gets

#62

Post by benchly »

My_Name wrote: post #55

They nearly have it in the article but don't take the next step, which is to realise that time is gravity. We are falling towards the future at the speed of causality. You can slow your experience of that by travelling really fast, or by being near something with a large gravity. Quantum particles can simply ignore gravity and time while we are forced to feel their effects due to our size, like a mote of dust can ign…

You might be interested in The Order of Time by Carlo Ravelli. Time and gravity are certainly linked, but from what I took away from the book (which is a lot to digest, even as non-mathy as it tries to be) is that Time is really heat. Heat moves only from hot to cold, dispersing in some entropic fashion as we move toward the final state of the universe, but in the meantime we can measure that time/heat "flows" at different rates, depending on how near or far you are from large bodies.

I likely need to reread it, though, as some of its ideas are a bit above my weight class when it comes to understanding physics. But, you may enjoy it!

Re: The closer we look at time, the stranger it gets

#63

Post by drcongo »

grishka wrote: post #44

There's another inscrutable mystery in physics, the nature of consciousness. Time might as well be an artifact of that . I'm surprised this article doesn't mention this possibility. Here's an interesting lecture about it: https://www.youtube.com/watch?v=YusrOYGAhqM

I got downvoted on here not so long ago for mentioning time as an emergent property of quantum consciousness so maybe it's controversial.

Re: The closer we look at time, the stranger it gets

#65

Post by Tor3 »

tacker2000 wrote: post #30
ChuckMcM wrote: post #14

This was perhaps my favorite part of Physics 390 ("modern physics") which was about quantum dynamics and relativity. The speed of light is defined in terms of a velocity (~300,000,000 m/s) but if you were traveling at the speed of light time stops (which keeps the rule that its constant in all frames of reference). That and time passes more quickly at higher altitudes and these days we can actually measure that. Wild…

Also see the twin paradox, which is related to this and equally fascinating. If one twin stays on earth and the other makes an intergalactic trip (with the speed of light), upon return, the one on earth will have aged much more than the one on the trip.

The paradox isn't actually when the twin is returning, the paradox is seen during the trip away from earth. Both are observing each other through telescopes, and both can see the clock on the wall in each other's home (a house, or for the twin, his space ship. Which has got a big window). And both can observe that the other twin's clock is moving at a slower pace than their own clock. And that's the paradox.

(p.s. the spacefaring twin doesn't have to move at the speed of light, and indeed cannot, it's enough to move at a "relativistic" speed, i.e. fast enough that this is actually measurable. With today's clock that doesn't have to be very fast actually)

Re: The closer we look at time, the stranger it gets

#66

Post by hhjinks »

kburman wrote: post #59
MaxikCZ wrote: post #38

Earlier quoted context omitted.

The fact that at speed of light time stops is just so bonkers to me. A photon is, from its point of reference, at the point of creation and at the point of destination at the same "time". Its literally seeing both parts of the universe at the same time, and since its traveled some distance over that time it cannot perceive, its essentially connecting 2 points in spacetime. If I understand it correctly, every photon e…

Have a question related to this, if a photon has zero proper time between emission and absorption, how should I think about the influence of later-created photons or fields on it? In our frame, we can interact with a photon long after it's emitted send it through a filter, bounce it off a mirror, measure it, etc. But from the photon's own “no proper time” perspective, does it make sense to ask how something created a…

>does it make sense to ask how something created after its emission could affect its path

The problem here is likely the concept of "after". It's relativity; what's "after" in our frame of reference isn't after in all frames of reference.

Re: The closer we look at time, the stranger it gets

#67

Post by raldi »

card_zero wrote: post #56
ben_w wrote: post #54

Earlier quoted context omitted.

> we can't measure how quickly it "flows" or at least how quickly we travel through it. I don't understand this, because it seems like "with a clock" is too obvious an answer, so surely you can't have meant what it sounds like it meant?

If we say that seconds "pass", at what rate do they pass? Could they pass at some rate other than one second per second? That would entail outer seconds (second seconds, if you like). Which also have their own rate at which they pass, so now we need a third-level "flow of time", and so on. So to say seconds "pass" is describing something else. They aren't moving.

You’ve never listened to a podcast at a rate of 1.5 seconds per second?

Re: The closer we look at time, the stranger it gets

#68

Post by oersted »

f3b5 wrote: post #60
tornikeo wrote: post #25

Not related to this article, but this post seems to attract so many cranks. Just look at other comments. The amount of weird (out-of-touch) comments on this post is fascinating.

Some of those might be AI accounts that found an ambiguous topic for upvote farming.

What might be the motivation for upvote farming on HN? There is the personal satisfaction of a carefully written comment being acknowledged and validated, but otherwise?

You do get some minimal upgrades with enough karma, like the ability to downvote. But it's not like you get any priority or special treatment, and the numbers are not exposed unless you open individual profiles.

I suppose it could be useful to give legitimacy to bot accounts to be able to inflate upvotes of some posts, but from what I've seen vote-ring detection is really good on HN.

Re: The closer we look at time, the stranger it gets

#69

Post by hhjinks »

ricardobeat wrote: post #13
slyfox125 wrote: post #9

We understand "time" in the context that we must: to subsist in order to procreate. The extent it exists outside of our own perception as we imagine it does, is debatable. Ultimately, time is our sensory interpretation of the world around us to facilitate our survival and thus, we may never make sense of it outside the constraints it exists within.

We know empirically that time only flows in one direction, it can’t be described as just a perception. You’d have had at least the tiniest of evidence that time sometimes flows backwards.

How would you measure time going backwards if you can only perceive it going forwards? How can you "experience" everything around you going "backwards" if that includes your memory? How can you determine that a specific moment in time was arrived at by time going forward, or by going backwards?

Re: The closer we look at time, the stranger it gets

#70

Post by oersted »

card_zero wrote: post #56
ben_w wrote: post #54

Earlier quoted context omitted.

> we can't measure how quickly it "flows" or at least how quickly we travel through it. I don't understand this, because it seems like "with a clock" is too obvious an answer, so surely you can't have meant what it sounds like it meant?

If we say that seconds "pass", at what rate do they pass? Could they pass at some rate other than one second per second? That would entail outer seconds (second seconds, if you like). Which also have their own rate at which they pass, so now we need a third-level "flow of time", and so on. So to say seconds "pass" is describing something else. They aren't moving.

I feel like you are overthinking it a bit, entangled in semantics. You can take any process that has a fixed frequency (like a clock), and measure the change in frequency in different situations, from the same point of reference. Moving that device at different speeds or into different places in a gravitational field. This is why satellite clocks move at a different rate than those on Earth.

Practically speaking, that's really what we care about when we talk about the speed of time. If some process takes a certain amount of time to complete, sending it to space and back, without changing anything else about it, might make it complete earlier from our point of reference.

It is actually about seconds per second, and there is an inner and an outer second as you say. There’s nothing wrong with that, because it is always a relative difference between two frames of reference. There are the seconds for our point of view, and there are the seconds for the device we are sending to space and back.

I think you are struggling to understand how to measure the absolute speed of time, but there’s no such thing, it’s always a comparison, it is relative.

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