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Space and time aren't fundamental properties of the universe

Started by Mrs Wogans lemon drizzle, December 01, 2021, 10:36:46 PM

Previous topic - Next topic

touchingcloth

Quote from: bgmnts on December 02, 2021, 01:11:17 AMSo that thing's spewing time back into the universe?

Precisely. That's why we're experiencing these curious time phenomena on the board.

Mister Six

Quote from: JesusAndYourBush on December 01, 2021, 11:20:48 PMA few weeks ago I watched episode 1 of Carl Sagan's 'Cosmos'.  A few days later Brian Cox's 'Universe' started and I watched episode 1. It was full of speculation (which to be fair Cox didn't try and hide, several times using phrases like "we don't actually know if this is true".)

Sagan was the Mack Daddy, Cox in comparison a mere shadow.  I saw ep.2 and that wasn't much better. I was at a gig when ep.3 was on and couldn't be arsed watching it on iplayer, and a few weeks ago I read an interview with Cox where he pinpointed the black hole episode as being the one with a lot of way out speculation so I decided to give that a miss as well.

That's not really Cox's fault, surely? Just an inevitable result of making a show about modern scientific understanding. Sagan's Cosmos is more than 40 years old, and astrophysics has come a long way since then. The cutting edge of science is equations on a whiteboard now - the telescopes and light spectrum readings and all that are often just a way to confirm or deny the theories.



Ambient Sheep

Quote from: touchingcloth on December 02, 2021, 01:11:57 AMPrecisely. That's why we're experiencing these curious time phenomena on the board.

That has nothing to do with Henry's cat and you know it.

Elderly Sumo Prophecy

I don't like Brian Cox's mouth. It's like he's smirking at me, even though he's not.

Twit 2


shoulders

The idea of Carl Sagan doing a tv show is great until you remember his speaking voice.

'Cos-mohwse'

Urgh

This is probably equally what Americans think about Confessor Brian Cox's accent.

Icehaven

I don't like Brian Cox and he was supposed to be making a guest appearance at a music festival I went to at Jodrell Bank telescope about 10/15 years ago, but he cancelled at the last minute and I think I was the only person there who was delighted. I think he was only going waffle about "phythics" for a few minutes anyway. I reckon he cancelled because he suddenly realised everyone would be yelling at him to do Things Can Only Get Better.


Alberon

I did watch about twenty minutes of an episode of Universe, but it was so glacially slow and devoid of information I got bored and switched over. There really is a need for a series, and I except probably a much cheaper one, where they can go into things in more depth. Maybe even link to webpages with more info. Just about everyone can pause TV now, they don't need to be so shallow and slow.

I think Universe could have been improved by having it presented by the other Brian Cox in Logan Roy mode.

greencalx

Quantum shit and cosmology is at the opposite end of physics to what I do, so I'm as much in the dark about what Cox might have meant as anyone else. I'd be surprised if he had the special theory of relativity (which is the one that unifies space and time) in mind when referring to something that he didn't understand, as this is fairly bread and butter stuff in a physics degree (although it makes my brain hurt on those rare occasions that I have to revisit it). I'm guessing he has one of the more esoteric theories (like string theory) in mind, but my understanding is that such theories don't (yet) hold any explanatory power beyond the more mainstream ones and are treated with caution by most physicists.

Quote from: Alberon on December 01, 2021, 10:46:42 PMAs far as Quantum Mechanics is concerned time doesn't seem to exist. How does that work?

I'm not sure that's true: the time-dependent Schrödinger equation certainly has time in it, although this is the classical notion of time (not relativistic spacetime). That said you can do relativistic versions (Klein-Gordon / Dirac) both of which are defined on spacetime. My relativistic QM is very rusty, but certainly the Schrödinger equation describes phenomena like the broadening of wave packets (particle starts off with a fairly well-defined position, but becomes more spread out over time) and scattering processes (chuck a proton at something, see where it goes). Indeed it's the latter that's used to analyse the very much time-dependent processes of smashing things together in particle accelerators to see what comes out.

Perhaps what you're referring to is that quantum and classical mechanics both involve reversible equations of motion, in the sense that if I run a system, pause it, turn everything round, and press play again, the system will retrace its steps. Another way of saying the same thing is that you can't tell whether a movie of a reversible system is being played forwards or backwards. This is an idealisation: clearly in the real world we can tell the difference between things going forwards and backwards. It's easier to hack irreversibility into classical mechanics than quantum mechanics, by including dissipative processes like friction that then allow you to identify an arrow of time. There's some recent(-ish) research on open quantum systems that have some sort of coupling to the environment and entanglement going on that I believe also includes dissipation, but this is yet to percolate into the undergraduate curriculum and is not that widely understood. I have a hunch that wave function collapse is a dissipative process, and you therefore need thermodynamics to properly understand it, as thermodynamics is the only branch of physics that properly respects irreversibility and dissipation. One of the things I'd like to do if a sabbatical year ever materialises is to dig into this literature and see if I'm right...

I'm fairly sure that didn't answer your question.

Inspector Norse




Johnny Yesno

Quote from: The Dog on December 02, 2021, 01:11:37 AMInside a black hole - and I do not really understand the details of this - time and space get really mixed up.

Yeah, that's a weird one. They swap over at the event horizon, meaning an object can only travel in one direction towards the singularity but can move backwards or forwards in time.

https://www.einstein-online.info/en/spotlight/changing_places/

touchingcloth

Quote from: greencalx on December 02, 2021, 09:11:11 AMOne of the things I'd like to do if a sabbatical year ever materialises is to dig into this

I bet you would, you dirty irreversibly-aged bollocks. I bet you fucking would.

Buelligan

Quote from: Mrs Wogans lemon drizzle on December 01, 2021, 10:36:46 PMBrian Cox

Not even the worst drummer in the Monkees.  Fucking hell, it's like they took smug and injected it into an egg whose nucleus had been removed.

Johnny Yesno

Quote from: Cloud on December 01, 2021, 10:56:46 PMThis is why I don't rule anything out any more like afterlife or being part of a simulation. 

Basic physics (and biology) says things like, well you're conscious as part of a brain function and when you die that's it, it's all very simple

Quantum is all "we know fuck all and some VERY WEIRD SHIT goes on". Just observing something can affect it? It's almost like a message from the simulation that everything you think you know is bollocks.

This is an illustration of why you need to understand the meaning of the terms or you end up in some woo territory pretty quickly. In this case, it's important to know that 'just observing something' usually means shining light on it.

The Dog

QuoteI'd be surprised if he had the special theory of relativity (which is the one that unifies space and time) in mind when referring to something that he didn't understand, as this is fairly bread and butter stuff in a physics degree

GR isn't though, and space and time switching roles inside the event horizon of a black hole spacetime isn't something you'd expect a particle physicist or a keyboard player to know, so I reckon that's what he was talking about.

Alberon

I've never liked the idea that a waveform collapses simply through being 'observed'. When I was a technician one of the experiments I set up for the students was the double-slit experiment.

https://en.wikipedia.org/wiki/Double-slit_experiment

Where light was shone through two slits and would form an interferance pattern on the other side. But even if you sent light through the slits one particle at a time it would still build up the same pattern. But if you have detectors on both slits the pattern does not build up. That is light acts like a particle and not a wave.

But the idea the universe alters due to if it is 'observed' or not doesn't make sense to me. So I'm much more in favour of the idea that the waveform doesn't collapse it simply expands to entangle the 'observer'.

Johnny Yesno

#51
Quote from: Alberon on December 02, 2021, 10:02:16 AMI've never liked the idea that a waveform collapses simply through being 'observed'. When I was a technician one of the experiments I set up for the students was the double-slit experiment.

https://en.wikipedia.org/wiki/Double-slit_experiment

Where light was shone through two slits and would form an interferance pattern on the other side. But even if you sent light through the slits one particle at a time it would still build up the same pattern. But if you have detectors on both slits the pattern does not build up. That is light acts like a particle and not a wave.

But the idea the universe alters due to if it is 'observed' or not doesn't make sense to me. So I'm much more in favour of the idea that the waveform doesn't collapse it simply expands to entangle the 'observer'.

As I intimated earlier, my understanding is that 'observing' particles and whatnot usually means interfering with them in some way, so it's not as woo as it sounds.

I don't know why I put 'observe' in quotes. I just shouldn't be surprised if my solar powered watch starts working when I take it from the darkness of my house into the daylight outside so I can read the face better.

Alberon

Yeah, that's why I put observer in quote marks.

It seems simpler to me for the entanglement to expand rather than collapse.

greencalx

I think wave function collapse is an idealisation of a much more complex process, possibly involving some combination of entanglement and dissipation.

shiftwork2

Fundamentally there are Skips and Picnics.

Rest of this shit is fucking gravy

shiftwork2

I had a lecturer who did the 'wave function mysteriously collapses when observed' caper before looking around for approval.  You could 100% tell that cunt didn't understand it.

shiftwork2


idunnosomename

Is it like not being able to have a wee when theres someone else there

Uncle TechTip

Quote from: greencalx on December 02, 2021, 09:11:11 AMQuantum shit and cosmology is at the opposite end of physics to what I do, so I'm as much in the dark about what Cox might have meant as anyone else. I'd be surprised if he had the special theory of relativity (which is the one that unifies space and time) in mind when referring to something that he didn't understand, as this is fairly bread and butter stuff in a physics degree (although it makes my brain hurt on those rare occasions that I have to revisit it). I'm guessing he has one of the more esoteric theories (like string theory) in mind, but my understanding is that such theories don't (yet) hold any explanatory power beyond the more mainstream ones and are treated with caution by most physicists.

I'm not sure that's true: the time-dependent Schrödinger equation certainly has time in it, although this is the classical notion of time (not relativistic spacetime). That said you can do relativistic versions (Klein-Gordon / Dirac) both of which are defined on spacetime. My relativistic QM is very rusty, but certainly the Schrödinger equation describes phenomena like the broadening of wave packets (particle starts off with a fairly well-defined position, but becomes more spread out over time) and scattering processes (chuck a proton at something, see where it goes). Indeed it's the latter that's used to analyse the very much time-dependent processes of smashing things together in particle accelerators to see what comes out.

Perhaps what you're referring to is that quantum and classical mechanics both involve reversible equations of motion, in the sense that if I run a system, pause it, turn everything round, and press play again, the system will retrace its steps. Another way of saying the same thing is that you can't tell whether a movie of a reversible system is being played forwards or backwards. This is an idealisation: clearly in the real world we can tell the difference between things going forwards and backwards. It's easier to hack irreversibility into classical mechanics than quantum mechanics, by including dissipative processes like friction that then allow you to identify an arrow of time. There's some recent(-ish) research on open quantum systems that have some sort of coupling to the environment and entanglement going on that I believe also includes dissipation, but this is yet to percolate into the undergraduate curriculum and is not that widely understood. I have a hunch that wave function collapse is a dissipative process, and you therefore need thermodynamics to properly understand it, as thermodynamics is the only branch of physics that properly respects irreversibility and dissipation. One of the things I'd like to do if a sabbatical year ever materialises is to dig into this literature and see if I'm right...

I'm fairly sure that didn't answer your question.


I assume stuff like this is why Cox takes the pop science route.

Chollis

I feel like a right cunt for enjoying The Planets and Universe now