The self-evident versus the counter-intuitive

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drossall
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Re: The self-evident versus the counter-intuitive

Postby drossall » 24 Nov 2016, 7:05pm

This may be only slightly on-topic, but I rather like the Dunning-Kruger effect, which says, to all intents and purposes, that only people who are qualified to do something are qualified to assess whether or not they are qualified.

Although Ben Goldacre paraphrased it as "being too stupid to know how stupid you are being".

landsurfer
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Re: The self-evident versus the counter-intuitive

Postby landsurfer » 24 Nov 2016, 7:53pm

TonyR wrote:Jevons' Paradox.

The Mpemba effect whereby a hot glass of water will freeze quicker than a cold glass of water if you put them in a freezer together.


It would appear that the Mpemba effect is false.
It was taken to the cleaners by a clutch of boffins on Radio 4 this evening.
The results of Mpemba and his mentor, in Tanzania, have proved to be unrepeatable.
Personally, I have always taken it for granted, and possibly a lot of others in the thermo dynamics industries have as well, aircon, cabin conditioning, etc etc ....
They even gave you a "try this at home" experiment to do ....

Unless...... It's all a Tory party plot of course ...........lol
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kwackers
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Re: The self-evident versus the counter-intuitive

Postby kwackers » 24 Nov 2016, 9:39pm

drossall wrote:This may be only slightly on-topic, but I rather like the Dunning-Kruger effect, which says, to all intents and purposes, that only people who are qualified to do something are qualified to assess whether or not they are qualified.

Although Ben Goldacre paraphrased it as "being too stupid to know how stupid you are being".

Or as I like to think; knowing you're stupid is the first step to lifting yourself above the masses.

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bovlomov
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Re: The self-evident versus the counter-intuitive

Postby bovlomov » 24 Nov 2016, 11:02pm

drossall wrote:This may be only slightly on-topic, but I rather like the Dunning-Kruger effect, which says, to all intents and purposes, that only people who are qualified to do something are qualified to assess whether or not they are qualified.

As far as I recall, the funniest part about the Dunning-Kruger research was that when incompetent people (who had a high opinion of their own competence) failed at their given tasks, it was explained to them how they failed, but this only served to increase their self-belief.

The lesson, I think, is that some humans have exceptionally robust strategies for avoiding uncomfortable truths about themselves. Trouble is, they are the ones usually to be found in charge of the rest of us.

Stevek76
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Re: The self-evident versus the counter-intuitive

Postby Stevek76 » 25 Nov 2016, 1:06pm

landsurfer wrote:It would appear that the Mpemba effect is false.
It was taken to the cleaners by a clutch of boffins on Radio 4 this evening.
The results of Mpemba and his mentor, in Tanzania, have proved to be unrepeatable.
Personally, I have always taken it for granted, and possibly a lot of others in the thermo dynamics industries have as well, aircon, cabin conditioning, etc etc ....
They even gave you a "try this at home" experiment to do ....

Unless...... It's all a Tory party plot of course ...........lol


? plenty of others have reproduced it, the problem is it's very inconsistently reproducible. I think it's one of those things that, thanks to rather rubbish mainstream media consistently misreporting the issues at hand gets very misunderstood. Even publications that give the pretence of being specialist quality science aimed can be pretty bad at times (eg new scientist).

The effect has been known to be highly inconsistent since the start (and has been documented long before Mpemba noticed it) which has the knock on problem that it's highly likely to not be a single matter, hence it gets 'solved' every few years under a highly specific set of circumstances where a certain contributory fact is highlighted - and there are several: supercooling, convection, progression of freezing differing, that latent heat of freezing is relatively large (equiv to ~80 to 0C cooling) etc and then these things tend to get a life of their own!

landsurfer
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Re: The self-evident versus the counter-intuitive

Postby landsurfer » 25 Nov 2016, 3:34pm

The boffins where sure it was not reproducible as the underlying issue is where the ice forms first.
On the surface.
In the centre.
Or at the bottom.
Possibly in strata between the temperature zones within the water.
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Flinders
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Re: The self-evident versus the counter-intuitive

Postby Flinders » 25 Nov 2016, 3:35pm

Walking through-semi-frozen puddles last weekend I noticed something I have noticed before- when a puddle has lots of bits of ice in, sometimes -but not by any means every time- the water seems sort of soupy and thicker than 'normal' water. I may just be imagining it, but I doubt it, when I notice it it is very notiecable, if you see what I mean.
It is a bit odd.....

A mathematician friend once spent about an hour explaining to me the goat-behind-the-doors puzzle. In the end we had to do it stage by stage, a bit at a time. It took a long time, but I did eventually 'get' it. However, I don't think I could explain it to anyone else. I just have a sort of hazy feeling it is about the combination of how probabilities are affected if you do something more than once, like the old coin-tossing thing.

Thankfully my work doesn't involve time and sequences as an issue; time is a constant not a variable, even if the job itself takes a lot of 'time' to do. Though it was not always so......

landsurfer
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Re: The self-evident versus the counter-intuitive

Postby landsurfer » 25 Nov 2016, 5:04pm

Schrodingers Cat paradox .... is that similar to the goat behind the doors ......

Would some one help me with the spelling!!! :roll:
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drossall
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Re: The self-evident versus the counter-intuitive

Postby drossall » 25 Nov 2016, 6:50pm

No.

In the Monty Hall problem, there really is a goat or a car behind each door. If you were allowed to go round and look, you'd see, but the goat or car would have been there all the time. This is a macroscopic effect - it happens with big things.

In quantum mechanics (which deals with subatomic particles), it's rather more bizarre. It can genuinely be said that some things don't have definite properties until you measure them. Rather, the probability actually describes what is happening.

So, in principle, if there's a subatomic event that may or may not happen, you could link it to some poison that would kill a cat in the same box. If the event has happened, the cat is dead. If it hasn't, the cat is still alive. However, since whether the event has happened can only be described by a probability (until you open the box and find out, i.e. measure it), the cat can be said to be alive and dead at the same time.

The key difference from Monty Hall is that it is not the case that, if you could only know what was in the box, the cat is either alive or dead. It really is both, with a certain probability of each, until you open the box and "measure" whether it is alive or dead, at which point it has to go into one state or the other (because the linked subatomic event then has to go into one or other state).

Remember, however, that this is a thought experiment. It's trying to put across what quantum mechanics means (or could mean). Quantum mechanical effects do not really happen at macroscopic scales, so it's doubtful that anything vaguely analogous could actually be put into practice.

More here, including that this is only one way of understanding quantum mechanics (which is pretty strange regardless of how you understand it).

landsurfer
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Re: The self-evident versus the counter-intuitive

Postby landsurfer » 26 Nov 2016, 8:24am

Thanks for that drossall.
My exposure to quantum mechanics is via reading popular science books, Hawking, Levey, Sagan etc.
That was probably the simplest explanation of the cat paradox i have come across.
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kwackers
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Re: The self-evident versus the counter-intuitive

Postby kwackers » 26 Nov 2016, 8:49am

drossall wrote:Quantum mechanical effects do not really happen at macroscopic scales

They've demonstrated the effects with decent sized clusters of atoms so who knows how big it could get!
I'm not sure getting a whole cat into a stable quantum state is ever likely to happen though, it's not even that easy to get them into a stable 'classical' state! :lol:

Here's something that puzzles me.

Light can behave as a wave, so it has a wavelength that implies it changes with time. Yet time doesn't pass for light, a photon that leaves a star on the far side of the universe 14 billion light years away hits my eyeball from its perspective the instant it left.
So if no time passes how can it change with time and thus where does its wavelength come from?

A physics guy I know tried to explain it to me but his explanation seemed to be based on the concept that a lot of names of properties we apply like 'wave' imply something they're not.
So I'm prepared to accept that they're not waves in the way we understand them but they still appear to be properties that change with time - time that hasn't passed...

drossall
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Re: The self-evident versus the counter-intuitive

Postby drossall » 26 Nov 2016, 9:48am

In my understanding, light has both wave-like and particle-like properties, and it's hard to say meaningfully that it is one or the other. In different situations, it's more helpful to use one or other description. Where you tend to get into a mess is where you try to mix the two. I think that's what you are doing. You could view it as closely related to the cat situation, where you have a live-dead duality; the cat is both but, once you've determined it to be one or the other, you can't go back.

So, you've got some live-dead light and, once you've found it to be live, you're trying to go back to it being dead, which is producing an irreconcilable contradiction. I said it was strange! So, wavelengths do not imply change for a particle, because that's like trying to view the particle as moving along the wave, which is trying to have both descriptions at once.

One famous experiment is this. Many of us know from school about diffraction gratings, where shining light through two parallel slits produces lines on a screen on the other side. This was classically held to be a proof that light is a wave (because the interference effect that produces the lines can only really be understood as a function of waves). Now envisage reducing the light source to a point where it is only emitting one photon at a time. You still get a pattern, even though the photon "must" have gone through only one or other slit, and could not have interfered with itself. Or could it?

For more, read a bit on wave-particle duality.

Health warning: I did a physics degree 35 years ago, and was not a top student. I'm likely not to be 100% accurate from an expert's perspective. It's fascinating stuff to think about though.

drossall
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Re: The self-evident versus the counter-intuitive

Postby drossall » 26 Nov 2016, 10:28am

Another way to realise that there's a problem with your question is this.

The photon is travelling forward at the speed of light (photons tend to do that). We all know that the fastest route between two points is a straight line. If the photon is also moving from side to side in a wave pattern, it's going to have to go faster than the speed of light to compensate.

Waves and particles are useful macroscopic ideas to describe light, which exhibits properties resembling both. Thinking of it as actually being one or the other, or even a hybrid, is not so useful. The world is a very strange (and therefore exciting) place, when you get into quantum mechanics and relativity.

If this hurts your head, don't under-estimate the crisis that these kinds of idea caused in physics when they emerged. Einstein, who had produced the really confusing idea of relativity, hated the even more confusing idea of quantum mechanics. There were real debates about whether (mathematical) models of the world could have "meaning" (such as light being a particle), or were just useful tools for predicting what would happen if you tried a certain experiment (and therefore, what would happen in the real world in whatever circumstances). Physicists now are brought up with relativity and quantum mechanics and, to some extent, only people who can cope with a pain in the head get to practice physics.

But, as I said, it can be pretty exciting if you accept all that (and if your maths is a lot better than mine).

kwackers
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Re: The self-evident versus the counter-intuitive

Postby kwackers » 26 Nov 2016, 10:47am

From what my physics mate said the photon doesn't move from side to side - because it's not really a wave...
He's a clever chap so I've no reason to think he's wrong. (He's a professor of physics at Liverpool, did design work on the superconducting magnets for the LHC and has a CV that makes as much sense as the maths behind string theory so I'm guessing he's qualified to answer, even if I can't figure out what it is he's saying half the time :lol: ).

I love reading about this stuff and it gives me something to think about when I'm out running (this and evolutionary biology/biochemistry) but quantum mechanics always seems to fall back to the 'Copenhagen Interpretation' -or 'shut up and calculate'...
What's amazing is how robust quantum mechanics actually is despite nobody having much of a clue.

drossall
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Re: The self-evident versus the counter-intuitive

Postby drossall » 26 Nov 2016, 3:08pm

kwackers wrote:From what my physics mate said the photon doesn't move from side to side - because it's not really a wave...

Quite. Except that, if you're saying the particle isn't really a wave, it's arguably not really a particle either, at least in the sense of a classical picture of one.