Quantum Physics

I can't say I really followed what she was proving.

But, your record player disk is rotating around the center (or axis or whatever), it isn't not rolling like a wheel down a slope. So much of that triangle infinate stuff probably doesn't matter.

Your figure near the edge is travelling a longer distance at a higher speed than the one nearer the center. 

So I suppose you can say that the "speed" setting the record player doesn't set the speed, but it sets the time of one full rotation.

Ahh, I see Halfie's here. So maybe the video's explanation can be explained.

the "speed" setting the record player doesn't set the speed, but it sets the time of one full rotation.- Amarie

{{ Yes but even with only one rotation, and fogoetting the exact speed of it turning, the thing near the middle of the wheel travels a lot less further to go round once than the thing on the outside, so you still have two objects leaving at same time, travelling at same speed, but over different distances, and yet they both arrival at end of the rotation at the exact same time!
Why cant we live in a sensible universe?! }}

I was away yesterday, then found all these videos waiting for me.  Including one about different expansion of the universe posted over a month ago I somehow missed.  That one I can dismiss by saying astronomy is a duct tape and twine sort of enterprise I don't really trust.  There was an earlier story I posted (but can't find now) which showed that differential expansion due to different mass densities in the universe may very simply explain either dark energy or dark matter, I don't recall which.  It would link to that video.

But on to the present one.  Petty - your questions about model soldiers is actually a totally different and very simple question.  Soldiers at the edge and halfway along the radius of the record player are NOT going at the same speed.  The one at the edge is travelling a larger circumference in the same time as the one on the smaller circumference.  Speed = distance/time so the one travelling the larger distance is travelling at a higher speed.  Nothing whatsoever to be confused about.

But the delightful and screamingly intelligent young lady you discovered is asking a very different question which knocked me sideways, and both her explanation and way of explaining things dazzled me.  To summarize: when rolling a wheel across the ground, it looks like the axle travels the same distance as the circumference, which seems not true because the circumference goes round and round while the axle goes straight.  She seemed to dispense with that by showing the bouncy cycloid a single point on the circumference travelled.  But putting paint on a smaller wheel and showing it paints the same length line as the larger wheel seems to make that confusing again.

Leave it to Galileo (centuries later he STILL comes across as freakishly brilliant) to put his finger on what's going on by converting circles to hexagons to demonstrate that the smaller hexagon is skipping.

But the above is just my added commentary.  I can't possibly explain things any better than that dear lady (who I'm quickly falling in love with seeing what else she has posted on her youtube channel) so I'll just leave you to rewatch it.

Soldiers at the edge and halfway along the radius of the record player are NOT going at the same speed.- Halfy

{{ But if its say on record going at 45rpm, then the whole thing, middle and edge is going at 45rpm? So the speed is the same? And if the speed at the edge compared to near middle is different why then why when its going at 45rpm doesn't the sound from a record sound like the chipmunks at the edge where its faster and slower near middle?}}

rpm is NOT speed. A person standing on the equator for one day has clearly travelled a much further distance than someone standing a pace off the pole. They both travel one revolution, but one has gone 40,000 km in one day, the other has gone about 6 meters. Clearly the one on the equator is travelling faster, even if they both did one revolution in one day.

For the same sound the record records the same number of ticks per second, whether on the edge or halfway down. If you had a record with a single pitch for the entire playing time and you looked with a magnifying glass, you'd see the edge had a stretched out pattern compared to halfway to the edge. Hitting the same number of ticks per second, but moving faster so they are more spread out.

Meanwhile I've got to work out how to steal that young woman away from her husband. I need her in my life. Not sure how to compete with a tall Frenchman in the romance department, but I'll work on it.

Actually, let me summarize the central mystery of the video that people seem to have missed.

We know that when a wheel revolves, both the circumference and a circle halfway to the axle go around exactly once; but the circumference maps out a longer distance than the half sized circle. But if you do the thing with paint that she did at two different levels, you get an equal length line from both! How can this be?

As Amarie points out the inner wheel is turning at a slower linear speed, so that the closer together points on the little wheel land at the same time as the wider spaced points on the bigger wheel. You can put spokes through them and have a dot on each wheel for each spoke. The confusion comes when you realize there's more room for dots on the outer wheel. How can this be when every line that goes through the small wheel could also go through the larger wheel and vice versa? It seems every point on the inner wheel is matched to one on the outer.

And so we come to types of infinity. But I really don't think I'm explaining any better than she did, so just go back and watch her video again.

{{ As if 2020 wasnt weird enough}}

Wiggles like this in the past have meant the field is close to doing a flip, which would be crazy!

{{ Oh good, just what we need, a planet devestating pole flip, combined with all our means of communication and control going down all at once! }}

{{ The Aliens are coming! That'd top off 2020! }}

Orcseses!

I think it's just a shockwave that sloshes a plasma, but not so much to make higher energy waves.

{{ Oh now thats just dull! Its got be aliens eventually- ideally some I can wave my towel at and catch a lift from off this insane rock }}

Are orcs any better than Vogons?

{{ Halfy and Dave- your help is needed.
Apprently thispaper solves th einformationpardox about Black Holes.
unfortunately just reading the synopsis at the start breaks my brain and makes it hurt!

'When absorbing boundary conditions are used to evaporate a black hole in AdS/CFT,
we show that there is a phase transition in the location of the quantum Ryu-Takayanagi
surface, at precisely the Page time. The new RT surface lies slightly inside the event horizon,
at an infalling time approximately the scrambling time β/2π log SBH into the past. We can
immediately derive the Page curve, using the Ryu-Takayanagi formula, and the HaydenPreskill decoding criterion, using entanglement wedge reconstruction. Because part of the
interior is now encoded in the early Hawking radiation, the decreasing entanglement entropy
of the black hole is exactly consistent with the semiclassical bulk entanglement of the latetime Hawking modes, despite the absence of a firewall.
By studying the entanglement wedge of highly mixed states, we can understand the state
dependence of the interior reconstructions. A crucial role is played by the existence of tiny,
non-perturbative errors in entanglement wedge reconstruction. Directly after the Page time,
interior operators can only be reconstructed from the Hawking radiation if the initial state
of the black hole is known. As the black hole continues to evaporate, reconstructions become
possible that simultaneously work for a large class of initial states. Using similar techniques,
we generalise Hayden-Preskill to show how the amount of Hawking radiation required to
reconstruct a large diary, thrown into the black hole, depends on both the energy and the
entropy of the diary. Finally we argue that, before the evaporation begins, a single, stateindependent interior reconstruction exists for any code space of microstates with entropy
strictly less than the Bekenstein-Hawking entropy, and show that this is sufficient state
dependence to avoid the AMPSS typical-state firewall paradox.'

Can you help explain it? }}

I'm afraid you're largely on your own.

All I can say is that for a long time a paradox about black holes was that when things fell in, the information that goes with them was destroyed. "So what?" you say. Problem is that information has been linked to entropy, and black holes seemed to be simplifying the universe, thus reversing entropy. The resolution was found by relating the information to the extra Hawking radiation that was produced when the black hole is fed. What's Hawking radiation? It's often explained by quantum fluctuations that create particle/antiparticle pairs, then one falls in and the other is left. Turns out this isn't really right but the real explanation is as far beyond me as that synopsis you printed is.

Where were we? Oh yeah - I have to say that abstract looks like hookum to me. Where did it come from?

{{ this is cool- Virgin have tested the first passengers in their hyperloop test track- basically you sit in a pod and its a vaccumm tube and you get shot along it at silly speeds! Travel of the future! }}

https://www.bbc.com/news/technology-54838982

I think this video does a pretty good job of getting across quantum mechanics, though at points you should ignore the equations they occasionally stick up and just look at the pictures (you should not ignore the pythagorean theorem, but other things).

the first half is about waves and vectors in classical physics, then it takes it into quantum. Gave me some nice new insights myself.

there has been recent experiments at CERN showing discrepencies from the standard model of particle physics. But all may be due to poorly done calculations.

https://www.yahoo.com/news/proof-physics-muons-magnetic-moment-153139108.html

I expect this may bear out. I'm rather agnostic on this but it makes sense. I do hope that similar calculations that make dark mater go away will also make it go away - I don't like dark matter.

{{ This is fascinating. }}

I had never heard of Theia before, its really interesting.

That is interesting. I've never completely bought evidence for the theory that the moon was formed by impact, but this adds corroborating evidence.

{{ This is cool.

'A project to create electricity from gravity has generated its first power at a demonstrator site in Edinburgh.
The Gravitricity system acts like a giant battery to balance the electricity coming from renewables.
Experts say such storage systems will be increasingly important as our reliance on wind and solar energy grows.
The system works by using excess power to raise heavy weights which keep that energy "stored" until it is needed. Electricity is generated when the weights are dropped.
It has been designed to be housed in old mine shafts rather than towers and in the UK could go to depths of 750m (2,461ft) - twice the height of the Eiffel Tower in Paris.
But in African countries, where it could be placed in holes specifically built for the job, the depth could exceed 2km (1.2 miles).
"For wind farms and things like that, the storage doesn't come naturally so it's really helpful to have other systems that are able to provide storage."
The company says it provides a cost-effective alternative to lithium-ion batteries which doesn't require rare earth metals like cobalt and nickel.- BBC Scotland

Mind you, 'Gravitricity', this is why you shouldnt let engineers name their own creations! }}

One of the most obvious and efficient energy storage systems possible; I think people just don't like the bulk and lack of portability or it would dominate.

I love this girl so, so much. She's a genius at explaining things.