21

New Theories / Re: Could quantum mechanics be wrong?

« on: 18/03/2024 13:33:48 »

There is more, a lot more to this theory.

And apparently you don't understand a bit of it.

Addressing the question in the title of the thread I think the answer is no.  The reason the answer is no is because quantum theory accurately predicts the outcome of various experiments.  It very well could be that there can be a better or more accurate theory that will replace quantum theory, but that does not mean quantum theory is wrong.  Newtonian gravitational theory is not wrong, it just does not cover all areas as well as General relativity.  Newtonian gravity will do just fine in trajectories of cannon balls or sending a space ship to land on the moon but it is not so good at determining the deflection of light due to a massive body for instance.

22

New Theories / Re: Could quantum mechanics be wrong?

« on: 18/03/2024 12:22:32 »

When the electron cloud absorbs a photon, the subsequent emission of a photon doesn't necessarily obey the law of reflection (angle of incidence = angle of reflection.) The same applies to refraction because the process of absorption and emission involves transitions between quantum energy levels within the atom, which can occur in any direction.

This is just a strawman argument since the absorption and emission of photons from electrons is not how refraction or reflection are explained.

23

Physics, Astronomy & Cosmology / Re: Gas discharge tube hydrogen

« on: 17/03/2024 22:12:33 »

Hi ES, I would have said 1Mv/m for normal air but I could be wrong. Many discharge tube use additional methods to start the initial ionisation, prior to avalanche occurring such as heated filaments in florescent lamps, a high voltage external conductor in xenon flash tubes and an auxillary electrode very close to one of the main electrodes in mercury vapour lamps(to start a local ionisation). High pressure sodium lamps and tin halide lamps use a high voltage source in series with one of the electrode supplies. The gas pressure plays a major role in the voltage needed to initiate ionisation, referred to as the strike voltage: the higher the pressure, the higher the necessary voltage and a lot of discharge lamps have to cool down after power interruption before reuse as the pressure is higher when hot. Many other factors may account for the discrepancies in the calculations: random cosmic rays as you suggested or low level radionuclides. Field emission as raised by Alancalverd may play a role(wild assed guess).   

24

Physics, Astronomy & Cosmology / Re: Gas discharge tube hydrogen

« on: 17/03/2024 11:27:24 »

This " An electron could be free of the nucleus only if it absorbs a photon raising its energy beyond the transition limit. " is missing the point of a gas discharge lamp.
The voltage gradient is big enough to pull the electrons out of the atom.
In some cases they have a hot filament which emits electrons and those can be accelerated by the field and when they hit an atom (or molecule) they ionise it and start a Townsend Avalanche.

25

Physics, Astronomy & Cosmology / Re: How many spots are produced from Stern-Gerlach apparatus that rotates?

« on: 16/03/2024 13:49:27 »

I remember this experiment from my long distant college days but I had forgotten it's name. I can't add anything of value, I do however have a question: how are the silver atoms entrained in a beam? the only way I can think of is electrostatic acceleration, that would lead to charged particles which are ruled out by the terms of the experiment.

26

Physics, Astronomy & Cosmology / Re: How many spots are produced from Stern-Gerlach apparatus that rotates?

« on: 16/03/2024 13:22:42 »

In the interests of pointless pedantry, Drs Stern and Gerlach did their experiment on Earth- which is rotating.
So we already know what happened.

27

Physics, Astronomy & Cosmology / Re: How many spots are produced from Stern-Gerlach apparatus that rotates?

« on: 15/03/2024 17:43:56 »

More interestingly we can send the electrons through a z-axis aligned apparatus and then send them through a y-axis aligned apparatus.

Ahem! SG1 device splits a single beam up/down relative to its incoming vector. You now have two beams U, D with different vectors, each of which is split left-right by SG2.

Problem is that vectors U and D are not parallel so you really need two SG2s to do the second split, but assuming you can do it, you get four exit beams UL, UR, DL, DR so I think

At the end of the experiment then,  the electrons near the North pole of the last apparatus were not necessarily near the North pole of the first apparatus, they could have come from the South pole in the first apparatus. 

is potentially misleading.

However the question is what do you mean by "slowly rotating"  the device? I can imagine a magnetic field that rotates with distance along the z axis, or in practice a series of SGs each slightly rotated with respect to the previous one, so if we ignore the essential divergence of the beams at each point, we'd get a circular distribution at the exit.   But I rather think we are ignoring the weight of the elephant!

And then it looks as though you have addressed the question in your second post anyway.

You might be interested in the umpteen ways we manipulate proton spins  in an MRI system!

28

Physics, Astronomy & Cosmology / Re: How many spots are produced from Stern-Gerlach apparatus that rotates?

« on: 15/03/2024 15:23:39 »

Overall, we end up with  four spots or locations for the electrons at the end with an equal intensity on the screen:   1/4  went up and left,    1/4 went up and right,  1/4 down and left,  1/4 down and right.

OK, as expected. Measurements taken along perpendicular axes would register no particular correlation.  I take it that the deflection is small enough that a single second device measures both outputs of the first device.

Now, what happens if you do the experiment slightly differently?   Instead of having two pieces of apparatus, with one just in front of the other,   we will use just one very long Stern-Gerlach apparatus and slowly rotate the apparatus while the electrons are travelling through it.    Initially the apparatus would be aligned in z-axis direction when the electrons enter it,  it would then be rotated so that the magnetic field was aligned in the y-axis direction by the time the electrons exit from it.

Not sure. A quantum measurement is already taken (collapsed so to speak) by the initial z-alignment, so at no point is the new angle not yet measured. I think it will carry this collapsed state through the rotation, leaving again two dots. Before, you were measuring a previously unmeasured y component. Not the second time.

That's my take anyway. Good question. I'm not enough of an expert to properly justify my response. Yes, it's a lot like sending light through a series of slowly changing angled filters.

29

Just Chat! / Re: Are the first year lectures the best?

« on: 13/03/2024 17:07:22 »

Not the sort of sentiment one expects to find in a science forum - it's the unknown and unexpected that pays the rent!

The first two years were mostly about learning to use the tools of the trade, which were pretty well polished and indeed "elegant" by the time they were handed to us. But the third year was all about applying them to real-world problems of steadily increasing incompleteness in the hope that we might go on to increase humanity's store of knowledge, save lives, or make a profit, in a world full of failures and uncertainties.

There are few tools more elegant than a Japanese saw, but its purpose is to turn rough timber into a house, so at some point the apprentice carpenter has to be introduced to a real tree, and no two are alike.

In a parallel life, I remember a very polished introductory lecture on Bernouilli's theorem, which, once we had mastered the art of getting off the ground in fair weather (ask any bird), gradually morphed into the least worst  procedure for ditching in darkness (very few survivors to date).

30

Just Chat! / Re: Does an infinitely long iron bar have two tangible endpoints? (Have mercy.)

« on: 12/03/2024 22:22:04 »

Before lasers came on the scene, this was known as the scissor paradox: how fast does the shadow move as you cut a light beam  with a pair of scissors?

But as with all paradoxes, it isn't paradoxical, just badly stated. The shadow (or laser spot) doesn't transmit information in a direction perpendicular to the light beam, and any information transmitted along the beam travels at c.

31

Physics, Astronomy & Cosmology / Re: What is included in a configuration space?

« on: 01/03/2024 19:39:19 »

Under "classical" rules you can know a configuration absolutely at any point in time, but (a) Heisenberg sensibly points out that you can't, (b) if you don't know the velocities of 3 particles in space, you can't predict anything about them and (c) even if you did and there was nothing else in the space, the 3-body problem still defies an analytic solution.

32

Just Chat! / Re: What is the difference between Beer, Lager and Ale?

« on: 27/02/2024 13:46:25 »

And it wasn't intended to provide potable water; it was intended to provide an alcoholic beverage which was robust enough to survive the trip without going off.

Hops is a strange plant.  Hops is an antibacterial, which is why the high level of hops was used in British ales sent on the long trip to India.  It can also cause hyperthermia in dogs if they were to eat the flowers.  I have been making beer for many years and I also grow a couple of varieties of hops.   

Some web info is suggesting there are hops in ale, beer and lager and I'm quite prepared to believe the order is
ale > beer > lager.

Actually I think beer is a general category.  IOW if you said give me any kind of beer at a bar, you might get an ale, a lager, a porter, a bock, a pilsner....

33

Just Chat! / Re: What is the difference between Beer, Lager and Ale?

« on: 27/02/2024 13:31:16 »

. The colour, as far as I know, comes from a large quantity of malt used in manufacture.

At least part of the difference is that the malt is kilned longer/ hotter so it's more caramalised.

34

Just Chat! / Re: What is the difference between Beer, Lager and Ale?

« on: 27/02/2024 13:28:24 »

India
Pale
Ale


And it wasn't intended to provide potable water; it was intended to provide an alcoholic beverage which was robust enough to survive the trip without going off.

35

Just Chat! / Re: What is the difference between Beer, Lager and Ale?

« on: 27/02/2024 09:24:11 »

The key is in the name. According to the guide at Tuborg Brewery 60 years ago (not all school trips are a waste of time) "lagered" means "kept" - a long, cold brewing period compared with ales that are brewed short and warm and should be consumed at room temperature.

The hops are not just for flavor but act as a preservative, preventing mold and bacterial growth. IPA was developed to provide potable water for ships travelling around Her Beloved Majesty's Empire and really took off in India, to the extent that the lagers served in Indian restaurants around the world (Kingfisher, Cobra....) are less fizzy and more flavored than others and actually developed from an ale.

36

Just Chat! / Re: What is the difference between Beer, Lager and Ale?

« on: 27/02/2024 09:14:34 »

You are all forgetting porter, the black stuff, as in Guinness. The colour, as far as I know, comes from a large quantity of malt used in manufacture. Beer is my favourite drink although I rarely exceed two drinks these days as opposed to my misspent youth when I drank all alcoholic drinks to excess.

37

Just Chat! / Re: What is the difference between Beer, Lager and Ale?

« on: 27/02/2024 00:05:03 »

Ale is apparently hopless, as in without hops.

Actually ales typically have more hops than lagers as I said earlier.  Sometimes a lot more hops, such as India Pale Ales.

38

Just Chat! / Re: What is the difference between Beer, Lager and Ale?

« on: 26/02/2024 23:42:31 »

From what little I know, Lager is cold brewed, with most of the fermentation going on at the bottom of the batch. Ale is the other way around: warmer and top fermenting.

Yep, the different yeast ES hypothesised, i think that is the biggest difference in the brewers world, followed closley by wheat beer.

Ale is apparently hopless, as in without hops.

39

Just Chat! / Re: What is the difference between Beer, Lager and Ale?

« on: 26/02/2024 22:29:07 »

Beer is the common term. Ale and Lager are more specific.
From what little I know, Lager is cold brewed, with most of the fermentation going on at the bottom of the batch. Ale is the other way around: warmer and top fermenting.

Not sure if the ingredient list is necessarily different. Sounds like a different process more than a different recipe.

40

Just Chat! / Re: What is the difference between Beer, Lager and Ale?

« on: 26/02/2024 22:16:23 »

In general there are 2 main types of beer, lagers and ales.  The difference is the kind of yeast that is used.  Ales have a stronger flavor and usually more hops (bitterness).  Lagers have a lighter crisp flavor.  Lagers are also usually served colder than ales.
Lagers yeast thrives in a cool environment as low as 40F.  Ale yeast thrives in around 70F.