Jim Al-Khalili And Quantum Mechanics

[vascop]

For those of you interested in Quantum Mechanics: I hope you watched Jim Al-Khalili's programme 1 of 2 last night on BBC4 at 9pm. Very interesting I thought.

[ToraToraTora]

damm missed it, do you know if it's repeated anywhere?

[jim360]

It's on iPlayer, so you should be able to watch it there. See:

[jim360]

I didn't watch it myself, by the way.

[ToraToraTora]

ok thanks

[Old_Geezer]

Thanks for the info. May try to catch next week's then.

[VHG]

It is complex stuff.

I did watch it, and TRIED to follow it, but even though he kept trying to show simple examples to explain certain theories, I still did not really understand much of what he was talking about.

He showed a machine at the end which was sending light beams through mirrors and so on, and he said if the result is below 2 Einstein was wrong, and if it was above 2 Bohr was wrong, but I did not really understand WHAT was happening and why the number TWO was so important.

I am not saying all of this is a reason not to watch it, but he does cover some complex ideas that are way above most people's heads.

[Old_Geezer]

Maybe he explains in one of his paperbacks ;-)

[Quizmonster]

As a total non-scientist, but a fan of Al-Khalili's programmes, I too got about 75% of it but the "TWO" part of it lost me as well, I'm afraid.

[Old_Geezer]

It is my guess that 2 is important because, if it was above 2 Bohr was wrong, and if it was below 2 Einstein was wrong !

Darn it, at this rate I'll have to knock the PC gaming on the head and run the iPlayer Einstein's Nightmare instead.

[Old_Geezer]

Watched it while my hard drive was being scanned.
(Couldn't get on with much else until that was done anyway.)

The 2 comes out from Bell's Theorem and the CHSH inequality.
http://en.wikipedia.org/wiki/Bell%27s_theorem

[Arksided]

I will give it a watch, however I do need Dr. Brian Cox to explain things to me with his jelly beans and stuff.

[Quizmonster]

OG, early in your link the following words are used, "an analogy (based on spin measurements on pairs of entangled electrons) to EPR's hypothetical paradox..."
This is part of an 'explaNATion'!?
I daresay it might well be to some but not to a person who is - as already cofessed to above - "a total non-scientist", I'm afraid.
But thanks for trying. I don't mind in the least understanding only 75% of what JAK has to say!

[jim360]

It's very difficult to explain the origin of specific numbers. Most obviously that's because they arise from the mathematical equations at the heart of the subject, equations often being inaccessible without understanding the notation and the concepts.

I'll have to familiarise myself with the experiment in question and if I get round to that I'll see if I can clarify things anyway.

[Old_Geezer]

IMO one often doesn't need to know how all the t's are crossed and the i's dotted to understand the general gist of something.

It has been a hindrance to me that in college I was always "at sea" unless I could understand where everything came from. And I do mean that nothing seemed to fit comfortably in my mind and feel understood until it all did (at least at some level). I think it may be because my memory has always been awful so learning rote is a big issue for me, but understanding how, I'm better at.

But for "popular science" stuff away from the colleges and work, I'm happy to know where the instructor is coming from. If I understand their conclusions and see what they ploughed through to get them, I'm confident their peers would have given it all a good going over.

[jim360]

In general I agree with you. I think it should be clear enough that Einstein and Bohr had competing theories that lead to distinct predictions and that this experiment can distinguish between them. It should be possible to go into more detail about how these predictions differ, too. Main reason I won't is because I need to read up on the subject first.

But exact numerical results require a whole different level of explanation and it's common that even experts in the field might not immediately understand the significance of a particular number. It could depend on the method used or the units or some wacky normalisation, or all sorts of other things. That makes sharing numbers tricky and often somewhat pointless.

[Peter Pedant]

I thought it was good and worth another go

John Stewart Bell was the son of travellers and they bust a gut to get him to Queens Belfast. And the fella made good.

Bells theorem was pretty hard to understand the wiki gives a definite non-proven verdict....

IN kuhns book - Planck is asked - oh Dr Plank how did you get the old professors to accept your new ideas - and he answers .... 'they died'

apparently the old have invested too much in their own old stupid ideas to say to the bright young men - 'hey you're right and I am wrong '

and I was irresistibly reminded of this when I heard the details of the long term argument between Einstein and ( the other guy ) [QM-boy]

and the fact that a fella ( Bell ) gave the possible answer in 1964
and everyone ignored him.....

[ToraToraTora]

brilliant program, the sheer brilliance of John Bell sorting out the Bohr/Einstien dicotomy was new to me. I think though that Einstien claimed the deck was stacked because he could not bring himself to go along with what he thought was just fantastical folly and that was the best explanation. Bohr was happier with the fantasy as is most of the physicists that have used quantum mechanics since but have no idea why it works they are just happpy it does! I also loved the curtain analogy that helped get the idea across. Yes I watched it on Iplayer. I now have it series linked.

[vascop]

The second program will be about quantum biology. Having read "The Mathematics of Life" by Professor Ian Stewart, which doesn't cover quantum biology, I'm really looking forward to watching it. I'm recording both programs and then making myself a DVD so I can watch them again and again if necessary.

[jim360]

Quantum biology sounds interesting, I'll try to remember to watch that one.

[bibblebub]

Just watched it, and the number 2 that was suddenly introduced for the Clauser/Aspect experiment was just the rhs of a probability equation that wasn't explained, just pre-written on a white board. This equation was similar to the Bell equation introduced a bit earlier but was not that one; indicating how such equations are derived would require a knowledge of quantum physics that only a handful (or less) of viewers would have so they just have to bring it into the show without explanation.