Enough with the questions about time, already

[pamosmusic]

I do not agree. :P

Yes, we remember your past life

[Strat-itis]

Petey with the grudge

[AdroitMage]

I do not agree. :P

[emanresu]

Hm. I've had an experience and history with nasty attitudes clashing in the internets, of course.
Once it turned out that one of the rude and obnoxious dudes revealed their past.
And it was the bad type. One of the horrible and sad ones.
From that moment, I never try to bite anyone anonymously in the internet.
Because the person in the other end is a mystery.

[AdroitMage]

I did have the Einstein book but don't remember much - I think you could get a decent handle on basic General Relativity if you have college level calculus. It has been 25 years since I studied it at uni, but there's a difference between being able to explore the basic properties of the Schwarzchild metric and solving the Einstein field equations which we never did (which remember Einstein himself didn't do.)

Interestingly they did show us a way the Schwarzchild metric does drop out of Newtonian mechanics, but that's not the real solution, just a cheat haha.

The necessary field of study is Reimannian geometry which I remember falling in love with but also I remember it not being too hard (although I was cleverer back then). It's the field that explains the geometry of curved surfaces in general, such as the transformations you need for map projections for instance, and is abstracted to the 4 dimensional spacetime of Einsteinian physics.

The brain busters for me were all Quantum Mechanics problems. Horrible. I hated it. It was possible the course was badly taught but I had real problems with the math..... GR was my jam.

If you really want to understand physics, you need to learn physics. Everything else is an imperfect analogy, really. But that means starting with Newton and Maxwell. Calculus and fields.



I doubt we'll observe directly, from what I understand. The particle accelerator necessary to detect it cannot be built in the foreseeable future (the energies are crazy). However, we may be able to infer Quantum Gravity through astronomical observations and cosmological models. But it's bit of a problem for fundamental physics. We were hoping to detect supersymmetric particles back in the 80s and 90s, but no luck, so that's ruled out a lot of early Quantum Gravity models.

Yeah, that's one area of science where I think actually finding it might be a pipe dream. I put might in italics, because I suppose there is a slight chance. Prolly part wishful thinking on the part of some physicists because finding "the gravity particle" would be a giant step forward in finding the elusive "theory of everything" that unifies classical physics and qauantum physics.

"The distinction between the past, present and future is only a stubbornly persistent illusion." - Albert Einstein

Here's one way that time could be described as an illusion. I asked the following question to AI. The answer is quite interesting:


If two people are In the exact same geographical location at precisely noon and they are both looking up at the Andromeda galaxy, but one guy is moving fast while the other observer is standing still, would they both be seeing the Andromeda galaxy how it was at the exact same moment?

Edit
No, they would not be seeing the Andromeda galaxy as it was at the exact same moment. This is due to the relativity of simultaneity, one of the key insights from Einstein's special relativity.

When two observers are in relative motion, they disagree about what events are simultaneous. Even though both observers are at the same location at noon and looking at Andromeda, the moving observer and the stationary observer will have different definitions of "now" for distant events.

The effect depends on the relative velocity between the observers and follows this relationship: the time difference in their simultaneity is roughly (v × d) / c², where v is the relative velocity, d is the distance to the object, and c is the speed of light.

For Andromeda, which is about 2.5 million light-years away, even a modest relative velocity creates a significant time difference. For example, if one observer is moving at just 100 meters per second relative to the other (about 224 mph), they would disagree about simultaneity at Andromeda by roughly 8 years. If the relative speed were closer to everyday highway speeds, the difference could be decades or even centuries.

So while both observers see light that left Andromeda approximately 2.5 million years ago, the moving observer's "slice of now" through spacetime at Andromeda's location corresponds to a different moment than the stationary observer's slice. This isn't just a measurement effect - it's a fundamental feature of how spacetime works when observers are in relative motion.

That was the answer from AI. Absokutelyv mind boggling. I think I need some weed now ???.

Here's another interesting fact related to time travel:

Time travel to the past and coming back to the present moment are possible and I can prove it beyond a reasonable doubt.

[Christian Miller]

There’s nothing in the laws of physics afaik that expressly forbids time travel. In fact as you may know Kurt Gödel massive troll that he was came up with an early solution to the field equations for a rotating universe that allowed time travel. This one’s come back in the news recently.

Physicists really don’t like reverse time travel and FTL (same thing depending on your reference frame) because it destroys causality. It’s an interesting fact that all the solutions that allow either time travel or FTL violate important Energy conditions in General Relativity which suggests that they are unphysical.

(That said I can’t quite understand why it’s ok for Dark Energy to exist and apparently violate but not negative energy density, but that’s mostly on my lack of understanding of the subject. As I understand it DE doesn’t cross the red lines FTL does.)

This creates the spectre of a sort of temporal censor built into GR, but I’m not sure if anyone has dug into why the maths works this way?


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[John A.]

Physicists really don’t like reverse time travel and FTL (same thing depending on your reference frame) because it destroys causality. It’s an interesting fact that all the solutions that allow either time travel or FTL violate important Energy conditions in General Relativity which suggests that they are unphysical.

David Hume and logic destroyed causality long before modern physics came along. Given the impossibility of defining causality without circular reasoning I would have thought physicists would be more stuck on that.

[RJVB]

It’s an interesting fact that all the solutions that allow either time travel or FTL violate important Energy conditions in General Relativity which suggests that they are unphysical.

According to current knowledge, laws and theories ... IOW, until someone discovers a way to take shortcuts through the space-time continuum?

Anyone who's been at Ikea's a few times knows that you can get to the casheers a lot quicker and with a lot less effort if you know the right shortcuts

David Hume and logic destroyed causality long before modern physics came along. Given the impossibility of defining causality without circular reasoning I would have thought physicists would be more stuck on that.

The joke thread is thataways (and religion has been trying to do all that since the dawn of times).

[Tal_175]

David Hume and logic destroyed causality long before modern physics came along. Given the impossibility of defining causality without circular reasoning I would have thought physicists would be more stuck on that.

In my understanding he didn't destroy causality as in he didn't prove that causality doesn't exist.He argued that our perception of causality cannot be considered a proof of its existence. Any observation and experiment based scientific field is based on certain practical axioms (not unlike mathematical fields). One them is that what we consider reality is based on multiple people agreeing on their sensory experience (with some obvious qualifications). Another one is the principle of induction. Every rigourous field builds on a set of carefully selected assumptions. I don't find Hume's insight particularly profound w.r.t. to the modern understanding of reality, cognition and formal frameworks of inquiry.

[pauln]

True, but I heard a physicist say that the movie Interstellar got the physics correct on that.

Wouldn't physicists need the correct physics to say the movie got the physics correct?

[pauln]

The effect depends on the relative velocity between the observers and follows this relationship: the time difference in their simultaneity is roughly (v × d) / c², where v is the relative velocity, d is the distance to the object, and c is the speed of light.

For Andromeda, which is about 2.5 million light-years away, even a modest relative velocity creates a significant time difference. For example, if one observer is moving at just 100 meters per second relative to the other (about 224 mph), they would disagree about simultaneity at Andromeda by roughly 8 years. If the relative speed were closer to everyday highway speeds, the difference could be decades or even centuries.

(v x d)/c^2 takes d and c as constants, so the answer (magnitude of disagreement of simultaneity at Andromeda) is proportional to v. With v at 244 mph the answer was 8 days, but at everyday highway speeds (e.g., 70 mph) the suggestion is decades or centuries. That suggestion is an inverse proportion indicating incorrect interpretation.

I calculate the answer using that equation:
305 days at 224 mph, not 8 days
95 days at 70 mph

ChatBot solving the problem for 224 mph at 1 mile separation and 0 separation:

1 mile separation approximately 1.3 x 10^(-14) days ?(practically 0)
0 separation: In this specific scenario where the two observers are at the same position (zero separation distance), there is no disagreement of simultaneity; they will observe the same events as simultaneous.
**Conclusion:** The value for the disagreement of simultaneity between the two observers with a relative speed of 244 mph and zero separation distance is **0 days**.

For all I know, both machines are hallucinating answers.

[John A.]

In my understanding he didn't destroy causality as in he didn't prove that causality doesn't exist.He argued that our perception of causality cannot be considered a proof of its existence. Any observation and experiment based scientific field is based on certain practical axioms (not unlike mathematical fields). One them is that what we consider reality is based on multiple people agreeing on their sensory experience (with some obvious qualifications). Another one is the principle of induction. Every rigourous field builds on a set of carefully selected assumptions. I don't find Hume's insight particularly profound w.r.t. to the modern understanding of reality, cognition and formal frameworks of inquiry.

That’s some sense of humor you got there.

[Christian Miller]

David Hume and logic destroyed causality long before modern physics came along. Given the impossibility of defining causality without circular reasoning I would have thought physicists would be more stuck on that.

Would you? Ok.

Causality is a big deal for physicists - esp relativists. It’s kind of built into the maths of Relativity at a basic level. It’s the reason why c is the cosmic speed limit. It’s quite a counterintuitive version of causality tbf but it’s integral to the theory.

It’s not hard to see actually, if you use a little basic math. In the special theory, It’s basically school child geometry with a twist, Euclid with a dimension - time - that appears as an imaginary number. the key property of an imaginary number is that when it is squared it becomes negative.

So if we calculate the hypotenuse of a triangle using this weird value we get a negative component

instead of
x^2 + y^2
You have

x^2 - t^2

(If we define units so that c=1)

when you have a world line x moving at c the space time interval - the hypotenuse vanishes to zero as both x and t become equal. So you’d need to have a triangle with negative length to break the light barrier. This makes mathematical sense I suppose but it does seem unphysical.

Actually, I prefer re time travel to think of it as conservation of energy in my own dumb way. If someone travels from the future they add their mass energy to the total in the universe. So you end up breaking a fundamental principle of macrocosmic physics.

I suspect it probably messes with the Second Law as well and no one messes with the Second Law.

But I expect it’s more complicated in reality with reference frames and so on.


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[Christian Miller]

If you can’t be bothered with any of that you can say that physicists are less interested with deriving concepts from first principles than they are in coming up with a model that is mathematically self consistent and makes measurable predictions about the universe. It’s quite hard to get both. Harder still to Ind one that isn’t quickly disproven.

If this wasn’t the case they’d never have derived Quantum physics as a response to problems like the Ultraviolet catastrophe in the late 19th century. It was very much ‘here’s this black box wave function thing, no idea what it represents, and it seems kind of mad and daft, but it seems to work.’ And the rest is pop science publishing history while the real world physicists quietly got on with it.

There’s not much philosophy in any of this.

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[pamosmusic]

Unfortunately the word “hypotenuse” is forbidden on this forum, Christian. You’re going to need to leave.

[RJVB]

There’s not much philosophy in any of this.

Nah, that's what (some) physicists indulge in after they retire - become emeritus in the speak of a scifi novel I once read

(you're also allowed to call it rambling, AFAIAC ^^)

[John A.]

If you can’t be bothered with any of that you can say that physicists are less interested with deriving concepts from first principles than they are in coming up with a model that is mathematically self consistent and makes measurable predictions about the universe. It’s quite hard to get both. Harder still to Ind one that isn’t quickly disproven.

If this wasn’t the case they’d never have derived Quantum physics as a response to problems like the Ultraviolet catastrophe in the late 19th century. It was very much ‘here’s this black box wave function thing, no idea what it represents, and it seems kind of mad and daft, but it seems to work.’ And the rest is pop science publishing history while the real world physicists quietly got on with it.

There’s not much philosophy in any of this.

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That science successfully ignores the problems of causality (and induction) was actually the point of my little joke, which turns out to have been smaller than I had hoped. If you have to explain the joke ...

[On a side note, I went to a specialized math and science high school. Some friends of mine had a band called "Ultraviolet Catastrophe". If I still didn't know a bunch of that circle of friends I'd definitely have stolen that band name.]

[Christian Miller]

That science successfully ignores the problems of causality (and induction) was actually the point of my little joke, which turns out to have been smaller than I had hoped. If you have to explain the joke ...

[On a side note, I went to a specialized math and science high school. Some friends of mine had a band called "Ultraviolet Catastrophe". If I still didn't know a bunch of that circle of friends I'd definitely have stolen that band name.]

Ok, I’ll take your word for it!

Otoh the same thought re band name had occurred to me. As I’m sure it has to generations of nerds.

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[Christian Miller]

Nah, that's what (some) physicists indulge in after they retire - become emeritus in the speak of a scifi novel I once read

(you're also allowed to call it rambling, AFAIAC ^^)

They usually do it quite badly because they haven’t spent a career reading philosophy

Writing science fiction is much less offensive, but again you do actually have to be able to write a novel. At least a bit.


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[Mick-7]

"The distinction between the past, present and future is only a stubbornly persistent illusion." - Albert Einstein

Here's one way that time could be described as an illusion.

Time is our gauge for measuring the rate of physical change, but in an infinite universe, this metric becomes simply a "parenthesis in eternity."

[AdroitMage]

"The distinction between the past, present and future is only a stubbornly persistent illusion." - Albert Einstein



Time is our gauge for measuring the rate of physical change, but in an infinite universe, this metric becomes simply a "parenthesis in eternity."

Fo sho, infinity is a mind boggling thing in and of itself. No matter how large anything is, compared to infinity, infinity is always infinitely larger. According to physics, our very own universe could already be infinite. Then, there's the question, could infinity really even exist, or is it sufficient to say that no matter how fast you travel, you'll never be able to reach the edge of the universe enough to qualify it as infinite, or is it actually an infinity already?

[Christian Miller]

The most mind boggling concept of all is that in an infinite universe there must exist a version of JGO that gives useful advice to jazz guitarists. Unimaginable, but true!


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[Mick-7]

The most mind boggling concept of all is that in an infinite universe there must exist a version of JGO that gives useful advice to jazz guitarists. Unimaginable, but true!

Well, I wasn't going to mention this but one night while doing a search on my Rod Serling internet browser (which is universe-wide web enabled), I came across a video archive by a guitarist named Christian T. Miller in a parallel universe and he shared some really innovative music concepts, unfortunately I was unable to download them.

[Christian Miller]

Well, I wasn't going to mention this but one night while doing a search on my Rod Serling internet browser (which is universe-wide web enabled), I came across a video archive by a guitarist named Christian T. Miller in a parallel universe and he shared some really innovative music concepts, unfortunately I was unable to download them.

He’s a fake


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[Mick-7]