Parallel universes? Quantum shit and stuff like that.

[hummingofevil]

Physics teacher with Theoretical Physics background here and I'll be honest I don't really know where to start with a lot of it. John Gribbin has written some very good books on quantum physics and string theory though to be honest I don't really get half of it and the half I do get comes from having studied the mathematics behind it. At a push I think I could probably explain quantum entanglement to you but I'm not convinced that even if you understood the concepts, my explanations would be convincing enough for you to think I'm talking bollocks. :)

For what it's worth I think this is the best bit of Physics done in decades.

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

The detection of gravitational waves. It proved the following in one swoop:

- Gravitational waves exist.
- Black holes exist (and this is a direct observation of them).
- Einstein's Theory of Relativity is verified (well more verified - more experimental evidence to support the ideas).
- The detail in General Relativity is pretty much spot on .

I'll add more but scan through that article and some of the values stated are mindmeltingly impressive but concrete enough so that it still seems real (unlike Quantum phenomena that are very much real and verifyable by experiment can seem so unreal compared with every day existence).

[touchingcloth]

One thing that's mad about quantum entanglement is that it's inescapable - even if you don't believe that they are entangled with each other and can communicate instantaneously across time and space, you're forced to believe something equally mad to explain the observed results.

It's been a while since I read around the subject - and I'm emphatically not a physicist - but as I understand it, it's something like:

1. Multiple properties of particles can't be measured at the same time due to the observer effect. Take speed and position - the only way to observe either thing about a particle is to bounce other particles off it not too dissimilar to bouncing radar off a car - because measuring the speed accurately disturbs the position and vice versa.

2. Particles can come in identical pairs through certain physical processes. You can make two identical particles which happen to be moving or spinning in opposite directions.

3. You'd think you could use point 2 to get around point 1 - measure the first particle's speed and the second one's position. You can't actually do this in practice, and the repeatedly observed result is that measuring the first particle affects measurements made on the second instantaneously. That's what's known as entanglement - even once separated by space the particles share some form of connection, and it seems to operate faster than light.

4. Things going faster than light is usually a sign that something has gone wrong with a calculation or a measurement somewhere, so taken at face value point 3 is disturbing enough, but so is any interpretation you care to dream up for it.

One option is that they aren't entangled, but just happen to coincidentally behave the same way at the same time in different places - it's not the fact that the first particle is having its speed measured which affects the position of the second, they just have speeds and positions which are in sync with one another. That's called "hidden local variables", and I'm not sure on the reasons why but as I understand it it's not a widely accepted explanation of point 3.

Another option is that of hidden non-local variables, that separately from the 2 particles there's some 3rd thing which communicates with them and tells them which speeds and positions they should have at any given time. That obviously combines elements of both faster than light and hidden local variables, and I'm not aware that it's seriously considered as a plausible option.

Remaining explanations run the gamut from "god does it" to "the measurements of point 3 are no good, we're doing it wrong and particles don't actually behave that way". That latter one is not a terrible explanation in itself, but the effects of point 3 are some of the most reliably repeatable experiments can be done, and with among the most precise results of any experiment - if point 3 isn't true or at least a good approximation of truth then arguably all of science needs to be reappraised.

I wish I had the grounding in maths to be able to follow the arguments in something other than the kind of layperson talk I've used above, but I do find the inescapable weirdness of it all fascinating. You can say you don't believe any given explanation, but you have to believe in something equally weird in its own way.

Just a btw but "speed" and "position" above aren't great examples of the sorts of properties which actually get measured for particles, but they're good stand ins when you're already talking in analogies.

[Alberon]

Part of my job as a Physics technician was to set up and run the double slit experiment as part of the undergraduate course.

Quantum mechanics is bloody weird. It's one of those things that if you think you fully understand it, you don't.

[Dewt]

Part of my job as a Physics technician was to set up and run the double slit experiment as part of the undergraduate course.

Can I have a hold of your long laser

[touchingcloth]

Wasn't the "cat in a box" thing originally supposed to highlight how all the quantum weirdness doesn't really scale up to a macro level? It's deliberately absurd, and wouldn't work in real life (not least because the cat is observing itself).

The thought experiment as originally conceived has the radioactive decay of a particle as the trigger - stick the cat in a box with a gun triggered by detecting a radioactive particle - as the decay of particles is itself a quantum process where it can be said (I think) that particles are both decayed and undecayed at the same time, if you stick one particle in as a trigger and then wait for the amount of time where the chance that it has decayed is exactly 50%, then the cat itself can be said to be both alive and dead at the same time. It isn't really both alive and dead, so it's really just a handy device because a dead cat is visual in the way that an alpha particle isn't.

[Zetetic]

That's called "hidden local variables", and I'm not sure on the reasons why but as I understand it it's not a widely accepted explanation of point 3.

There's a bunch of experimental evidence that shows that you don't get the right results from a local variable theory, at this point. (And the "maybe we're just bad at measuring it" get-out is increasingly untenable.)

Another option is that of hidden non-local variables,.. and I'm not aware that it's seriously considered as a plausible option.

It's basically the same as giving up, isn't it?

("God does it" is a form of hidden non-local variables, presumably.)

[MinnieTimperley]

Cant even get my head around what is at the end of an infinite universe.

[Kryton]

Physics teacher with Theoretical Physics background here and I'll be honest I don't really know where to start with a lot of it. John Gribbin has written some very good books on quantum physics and string theory though to be honest I don't really get half of it and the half I do get comes from having studied the mathematics behind it. At a push I think I could probably explain quantum entanglement to you but I'm not convinced that even if you understood the concepts, my explanations would be convincing enough for you to think I'm talking bollocks. :)

For what it's worth I think this is the best bit of Physics done in decades.

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

The detection of gravitational waves. It proved the following in one swoop:

- Gravitational waves exist.
- Black holes exist (and this is a direct observation of them).
- Einstein's Theory of Relativity is verified (well more verified - more experimental evidence to support the ideas).
- The detail in General Relativity is pretty much spot on .

I'll add more but scan through that article and some of the values stated are mindmeltingly impressive but concrete enough so that it still seems real (unlike Quantum phenomena that are very much real and verifyable by experiment can seem so unreal compared with every day existence).

So this might be a stupid question but how generally accepted is it that gravity itself might be responsible for such changes in observation? That's the gist I'm getting, but I also understand it's just one of a few theories? I honestly don't know.

[Kryton]

Or let me rephrase it, is gravity a factor or a result?

[Mister Six]

Cant even get my head around what is at the end of an infinite universe.

IIRC there is no "end" to the 3D universe we inhabit - it all just curves in on itself, kind of. As a result everybody is at the "centre" of the universe, because everything else extends out (and around) them, no matter where they are in relation to one another.

[touchingcloth]

There's a bunch of experimental evidence that shows that you don't get the right results from a local variable theory, at this point. (And the "maybe we're just bad at measuring it" get-out is increasingly untenable.)
It's basically the same as giving up, isn't it?

("God does it" is a form of hidden non-local variables, presumably.)

All very good points, and I don't think the "bad at measuring" thing holds much water. It's a bit like evolutionary science in that there are so many different experiments and lines of evidence explaining the same thing - there was a point where you could rubbish fossil evidence or DNA similarities in isolation, but taken together along with the ton of other forms of evidence it's just not tenable to disagree with evolution in some form without an appeal to magic.

[Schrodingers Cat]

IIRC there is no "end" to the 3D universe we inhabit - it all just curves in on itself, kind of. As a result everybody is at the "centre" of the universe, because everything else extends out (and around) them, no matter where they are in relation to one another.

It depends on who you ask. We still don't know enough to give a firm answer really. (Or at least that was true the last I checked) Generally it is regarded as finite, but limitless, so as you said, that it curves back on itself i.e. if you were to hypothetically travel far enough, you would arrive back where you started. Others seem to think that you could keep going forever without anykind of boundary, but would eventually just stop seeing matter. The problem is we don't know the shape or density of the universe. This curvature of spacetime would have huge implications on the ultimate fate of the universe - an open universe keeps expanding forever, a flat one stops and holds a(n essentially) fixed size, and a closed niverse would collapse in on itself (the so-called big crunch).

The whole thing of us being at the centre is a consequence of the big bang. Because the universe was infitesimally small at te time the big bang happened at all locations at the same time. So wherever you are, it was where the bang happened i.e. the centre.

[BlodwynPig]

IIRC there is no "end" to the 3D universe we inhabit - it all just curves in on itself, kind of. As a result everybody is at the "centre" of the universe, because everything else extends out (and around) them, no matter where they are in relation to one another.

Winds of time are blowing through me

[Dewt]

[Alberon]

It depends on who you ask. We still don't know enough to give a firm answer really. (Or at least that was true the last I checked) Generally it is regarded as finite, but limitless, so as you said, that it curves back on itself i.e. if you were to hypothetically travel far enough, you would arrive back where you started. Others seem to think that you could keep going forever without anykind of boundary, but would eventually just stop seeing matter. The problem is we don't know the shape or density of the universe. This curvature of spacetime would have huge implications on the ultimate fate of the universe - an open universe keeps expanding forever, a flat one stops and holds a(n essentially) fixed size, and a closed niverse would collapse in on itself (the so-called big crunch).

The whole thing of us being at the centre is a consequence of the big bang. Because the universe was infitesimally small at te time the big bang happened at all locations at the same time. So wherever you are, it was where the bang happened i.e. the centre.

Everywhere looks like the centre of the universe because of the way space expands. Going back to 2D Flatland it could be like a balloon. Put dots on it to represent galaxies and then inflate the balloon. The dots grow further apart without moving. That's sort of how it works in our 3D universe. Because the speed of light is impossible to surpass we can never even travel to all the universe we can see. And as the universe expands and ages fewer and fewer galaxies will be viewable until only the Local Group of galaxies are left.

It is possible the universe is literally infinite in every dimension, but there's no way to ever tell. If it's beyond 46.5 billion light years away it's effectively in another universe as we can never go there or even see it. If the universe is infinite in every direction then there are an infinite number of copies of us living lives similar to ours - all the parallel worlds existing in just one universe. Even if the universe is infinite in all three dimensions it can still be a finite brane drifting in an higher dimensional space.

[Schrodingers Cat]

It's basically the same as giving up, isn't it?

("God does it" is a form of hidden non-local variables, presumably.)

Not that physicists are entirely above that kind of thing!
I mean, my favourite topic is Dark Matter and Dark Energy, which is entirley a placeholder solution until we find something better. For those who somehow haven't heard of it: we can only account for about 4% of the universe. This is made up of what we call lumious, baryonic matter. As in, it emits or reflects light and is made up of baryons. We know Dark Matter must exist because there's a huge amount of missing mass - this was observed because distant galaxies are spinning much faster than they should be, so conservation of anglular momentum, there must be something missing. Unfortunatley, we have no idea what.
"So 90% of the universe is missing?"
"yes"
"OK, so what are we looking for?"
"Dunno"
"Where are we looking for it?"
"Dunno"
"You're certain its missing?
"Yes"
"Bugger"
The usual explanatiosn we have rely on what's called Supersymmetric particles we haven't observed before and last I saw we were running out of energy space for. Even if we did find these SUSY particles, it still leaves the questions "why have we not seen them before even though they apparantly exist in huge quantities in the universe? Maybe if we find them it will answer that for us, who knows?
Dark Energy is even weirder and tries to explain why the universe's expansion is accelerating. I know much less about this, other than we barely understand it at all.

[Alberon]

I think we're getting close to working out what Dark Matter is, but as for Dark Energy... We're still pretty much stumped on that.

[touchingcloth]

Not that physicists are entirely above that kind of thing!
I mean, my favourite topic is Dark Matter and Dark Energy, which is entirley a placeholder solution until we find something better. For those who somehow haven't heard of it: we can only account for about 4% of the universe. This is made up of what we call lumious, baryonic matter. As in, it emits or reflects light and is made up of baryons. We know Dark Matter must exist because there's a huge amount of missing mass - this was observed because distant galaxies are spinning much faster than they should be, so conservation of anglular momentum, there must be something missing. Unfortunatley, we have no idea what.
"So 90% of the universe is missing?"
"yes"
"OK, so what are we looking for?"
"Dunno"
"Where are we looking for it?"
"Dunno"
"You're certain its missing?
"Yes"
"Bugger"
The usual explanatiosn we have rely on what's called Supersymmetric particles we haven't observed before and last I saw we were running out of energy space for. Even if we did find these SUSY particles, it still leaves the questions "why have we not seen them before even though they apparantly exist in huge quantities in the universe? Maybe if we find them it will answer that for us, who knows?
Dark Energy is even weirder and tries to explain why the universe's expansion is accelerating. I know much less about this, other than we barely understand it at all.

There's also inflationism as an explanation for the very early universe's group as a similar fudge of the numbers, though as I understand it there are cases to be made that dark matter and energy are real things rather than just hacks to make the observations make sense, when things like quantum entanglement are overwhelmingly likely to be a good explanation of the way nature actually works.

[Schrodingers Cat]

There's also inflationism as an explanation for the very early universe's group as a similar fudge of the numbers, though as I understand it there are cases to be made that dark matter and energy are real things rather than just hacks to make the observations make sense, when things like quantum entanglement are overwhelmingly likely to be a good explanation of the way nature actually works.

Oh they're definitley real things. In the sense that something is there that can be measured and observed. We're just not clear what, so called it 'dark' as in mysterious and decided ot figure it out later. All things in physics start out as that - make a prediction, observe, change the science to fit the new observation. They were just so inexplicable (to start with) we had to coin a new term for them.

Entanglement is a bit different because it essentially violates existing accepted physics. But has also been observed. So, much like the aforementioned problems with gravity and QM not working on each others' scales - somethings gotta give. We clearly do not have a complete view of matter and energy on a fundametal level which works on all scales.

[hummingofevil]

Or let me rephrase it, is gravity a factor or a result?

One thing that I can see as being confusing is the idea that this observation is relying on the idea that the pulsar exists (well existed 1.4 billion years ago) and therefore there is gravity that causes this deflection but the observation of the deflection is itself is proof of the pulsar being there. I am not sure but suspect there was previous indirect observation of the black holes being there in the first place.

The simple equivalent is if you see a duck bobbing up and down on the edge of a pond it the same size wobble could be caused by a small stone being dropped close to it or a big stone thrown in on the other side of the pond. These are small but these are far away. But how do we know the difference. I'll have a read up tomorrow about this specifically.

Anyway, the way I think about it is if you imagine two blackholes spinning around each other then each one is distorting space time around it. At the point in the orbit where they are lined up one behind each other as we look at them then at that point their is a slightly bigger pull (using Newton's Law of Gravitation)  later where they appear with us to form the corners of a triangle. The effect of gravity changes ever so slightly in those two different positions. As the system is orbiting so it cycles through these two extremes and the overall effect is that is wobbles the space-time on Earth by a tiny amount.

Like looking at a bottom of a pond or a star twinkling, if you look at something through something that is moving then it appears to wobble. In this experiment's case it is actually space-time itself that is wobbling.

Anyway, the numbers that jump out to me is two blackholes, one x35 the mass of the Sun and the other x30, orbiting each other 350km apart (Newcastle to Manchester pretty much) at 200,000,000 m/s of 60% the speed of light and 75Hz (75times per second - which is basically the frequency of the bass line to Double 99's Rip Groove).

That is a lot of energy. When they combine in a 0.2s time they radiate more power than the rest of the Universe combined and this causes a deflection of a laser 1.4 billion light-years away (light travelling at 300,000 km every second for 1.4 billion years) that moves  less than the diameter of a proton over a distance of a km. That is insane to me.

[Sebastian Cobb]

Or let me rephrase it, is gravity a factor or a result?

[JesusAndYourBush]

So the next thought is what if we have a camera there, but don't record anything? make no observations? Immediatley, behaved like a wave again! Apparantly, nature knows when its being observed.

Hmm, I wonder what would happen if a camera was recording but the viewfinder was covered up so nobody could see what it was recording, and the tape was destroyed afterwards without anyone watching it.

[idunnosomename]

would anyone like to help me run a double slit experiment and solve quantum mechanics? lovely ladies only need apply

[JesusAndYourBush]

I mean, my favourite topic is Dark Matter and Dark Energy, which is entirley a placeholder solution until we find something better. For those who somehow haven't heard of it: we can only account for about 4% of the universe.

If the universe is infinite and we can only see a fraction of it, surely the bit we can't account for is the bit we can't see?

[checkoutgirl]

I have been to a parallel universe before.  It was exactly the same as this universe except I hadn't shaved yet.  Now I am back in this universe and lo and behold I have shaved.

Alien Gives Man a Beard

[Alberon]

If the universe is infinite and we can only see a fraction of it, surely the bit we can't account for is the bit we can't see?

Nope. Anything beyond the observable universe is effectively not in our universe at all any longer as it can have no influence at all on what we can see. Dark Matter makes up a large proportion of every galaxy we can see and Dark Energy is accelerating the expansion of the observable universe.

[MinnieTimperley]

Winds of time are blowing through me

We none of us can hold back the winds or even the hands of time BlodwynPig  none of us.

[DistressedArea]

Turns out that all the different universes aren't exactly parallel. Some genius discovered they were slightly askew, like they'd been dropped or knocked. Spent his life trying to make them all line up, drove him mad in the end.

Before he died, he designed a kind of quantum comb he said could be used to sort out the mess. Was an amazing technical achievement that would have destroyed all life in the universe.

Dumb boffins.

[bakabaka]

We none of us can hold back the winds or even the hands of time BlodwynPig  none of us.And it's all moving relative to me.

ftfy

[chocolate teapot]

https://www.highsnobiety.com/p/nasa-scientists-parallel-universe/?utm_medium=Social&utm_source=Facebook&fbclid=IwAR1vKMlwdoeBbDVeoJupHgT0xZsRfbz6kI0hKqJQgS3eRpsF812U19afLKM#Echobox=1589963777

"They discovered that the random noises they had recorded weren't signals coming from space but rather coming up from the earth. The finding implies that these particles are actually traveling backward in time, suggesting evidence of a parallel universe, where time is in reverse."

Reverse from what point though? the end of time going backwards?