1

Physics, Astronomy & Cosmology / Liquid surface waves in an acoustic resonator

« on: 15/11/2024 03:30:53 »

That sounds like a fancy title for what happens when you partly fill a wineglass and rub the edge.

Well, it is. The acoustic waves in the glass see a response in the liquid in the glass--waves start forming.
The kinds of waves can depend to some extent on the kind of glass. With lead glass, it seems to be easier to get a standing radial pattern on the surface of the water.

My conjecture is that these waves are not because the bulk of the liquid is vibrating, the surface pattern can't be very deep. So it's likely entirely electrostatic--the glass is vibrating so is producing an electric field displacement, this is projected over the surface of the water.

But I bet that's not the only causative agency--plasma physics is complicated and, the dipole moment of water molecules means it does act somewhat like a plasma does, when subjected to an oscillating electric field. The difference between tension at the surface and tension below it is why the surface responds and the pattern isn't destroyed.

Or is this all off the wall?

2

General Science / Is ChatGPT better than it was?

« on: 27/10/2024 10:31:17 »

My experience with this AI has been mixed. Sometimes it makes good suggestions, but often it gets repetitive.

I can get it to agree with me about things I know are true, or see if it disagrees when I intentionally say something wrong. Going back over questions you've had a response to, isn't usually worth the effort.

Anyone else with maybe better results out there?
I noticed there are quite a few "GPT" options, including coding tutors, resume writers, ... I'm impressed. At least, with the number of them.

3

Physics, Astronomy & Cosmology / Theoretical information

« on: 21/10/2024 20:50:08 »

With all the fuss about information entropy having the same kind of equation as thermodynamic entropy, and information theory being about how much structure or hierarchy there is in ah, the system under consideration, I've got a question.

My question for the pundits is, how much information is there in a scientific theory? Can it be compressed, transmitted and received, this information, which would be a necessary thing for it to "be" information . . . ?

But, is the question meaningful? If it is then it must be about information, per se. If not, . . .

4

That CAN'T be true! / Earthquakes and Presidents

« on: 06/08/2024 21:57:17 »

One Vladimir Keilis-Borok, a Russian geologist, developed a theory for predicting earthquakes which, when he collaborated with a colleague, Alan Lichtman, became a theory that predicts the outcome of US presidential elections.

So that has to be an example of looking for a pattern somewhere and then seeing the pattern somewhere else entirely. And it just so happens it's easier to predict a presidential race in the US than it is, still, to predict an earthquake, even in California.

Why though, to all the above? Why does it work or succeed, but fail in its original domain, this pattern-recognition theory, also why is Alan Lichtman a household name, but the other guy isn't?

5

Just Chat! / Political joke

« on: 31/07/2024 21:59:19 »

Two of Darth Vader's minions walk into a bar.

The bartender asks, "So how's the planet conquering business, guys?"
One of the minions says, "Well, you know, gain a world, lose a soul" . . .

6

Just Chat! / Cannibal rap

« on: 02/03/2024 09:14:57 »

You will have to imagine Anthony Hopkins doing that wine-savouring thing to a rap beat.

Interspersed with verse like so

" 'Ullo John, got a nice chianti? Allo John, got a nice chianti?
I've got some lovely fava beans.
I've got some lovely fava beans.
vsst!, vsst, vsstt! vsstt!  vss vsst vss . . "

And so on. Should get the street crowd going.

Apologies for my dry sense of humour.

7

Just Chat! / Is Category Theory the well of mathematical philosophy

« on: 28/02/2024 09:30:53 »

Despite my obvious disdain for what passes for the usual sense of philosophers, the meaning of the word does still have a certain, um, categorical significance.

I'll say that the Theory of Categories does seem to be a kind of mathematical heaven, for people with PhDs.
I get that impression watching some lecturers bang on about modules and algebras and what have you.

I think some of the female lecturers are very good, reassuring about all the abstract ideas that her students will be tested on, so it's about the things they need to figure out by themselves, given what they know about rings, fields, groups etc. It's a bit like psychiatry for math majors.

Anyways, does anyone here have any interest in this stuff, or some understanding of how far it all goes, this attempt to codify all mathematical objects and relations between them? or how doing this appears to simplify things considerably, in that mathematics is actually mind bogglingly simple? The general linear group is everywhere, as they say>

8

Physics, Astronomy & Cosmology / Graph of a group

« on: 25/01/2024 21:06:09 »

In this Youtube vid, the author explains how to construct two graphs, and use them to confirm that both preserve a group structure. It isn't about the Rubik's cube, which is used as an example of symmetry (i.e. a group).

The structure of a group is determined by the group operation; if the operation is preserved the two representations (graphs) are homomorphisms.

It's in French, but with an English translation. The diagrams and graphs are what give the game away here.

9

Just Chat! / My Jonny Clarke impersonation

« on: 18/01/2024 04:10:29 »

This is about a place that actually still exists. It's a suburb that was once basically a railway station and a big railyard.
You get the idea.

Evidently Frankton town

Frankton, Frankton, you're a load of bloody plankton.
Frankton, Wankton, I did not get thanked in,
Frankton.

My Dad once dranked in,
And I once banked in,
Frankton

The streets were manked in,
The Pub bloody stanked in,
Me account got blanked in,
Frankton.

Frankton, Wankton, don't get too skanked in;
You won't get bloody thanked in,
Frankton.

10

Physics, Astronomy & Cosmology / What is the Hopf gauge?

« on: 15/01/2024 09:01:43 »

I heard someone say something thought-provoking on a Youtube vid about the Hopf fibration.

This guy is some mathematician, a professor, and he said the Hopf fibration is our reality; I assume he meant something like the universe is a principal Hopf bundle.

?

11

Just Chat! / Trump's legal problems

« on: 08/01/2024 17:06:02 »

There isn't much on this site about the guy, you know, orange face, yells a lot. Yeah, him.

So currently he has four major indictments in four different states. My summary goes like this.

He is about to lose his New York real estate business--a Demolition Derby in Manhattan.

He is waiting to find out if the Supreme Court can save him from being convicted of, well, treason I guess--A Dark and Stormy Day in D.C.

He has that RICO indictment--A Rainy Night in Georgia.

And coming in last, the classified documents indictment for obstruction--a Fart in a Hurricane in Florida.

12

Just Chat! / Are you a Dick?

« on: 20/12/2023 19:56:02 »

Seriously.

Dick is a nickname for Richard, which starts with Ric. This Old-Germanic word, 'rik' means leader or ruler. The word rich used to mean wealth in the sense of land, a rich was a kingdom or earldom or what have you. We also today have the old meaning of a reach of land, and so on,

Anyways, the name Richard used to mean strong ruler or leader. Henry, another common regal name, is from Heinrich and guess what? The name means one leader. The German reich is cognate with the old meaning of land as a kingdom.

Derek, is from Theodoric, Frederic means peaceful leader. There are most likely a lot more.
But if you are a Dick, it means you have a modified version of Theodoric as a substitute for what your actual name means, as above.

13

Geek Speak / Variation of the three wise men puzzle

« on: 16/11/2023 23:32:50 »

Since this is a problem in logic I thought this place would be appropriate.

So here goes.

The traditional version of this puzzle is as follows.
A certain king wishes to determine which of his three wise men is the wisest. He arranges them in a circle so that they can see and hear each other and tells them that he will put a white or black spot on each of their foreheads but that at least one spot will be white.  He then offers his favor to the one who will first tell him the color of his spot. After a while, the wisest announces that he knows the color of his spot. How does he do this?

In my variation, the three men are blindfolded first, the spot of paint is applied, then the blindfolds are removed. One of the three men keeps his eyes closed and "after a while" announces he knows the color of his spot. How, using similar logic for the traditional version (which I have intentionally not supplied) does it work out?
A hint, it relies strongly on reasoning about what other wise men would reason, given the situation described.

14

Just Chat! / What's the difference between fair and balanced

« on: 15/10/2023 22:45:12 »

If you type "fair and balanced" into google's search bar, most of the hits are about the journalistic meaning.

Given the situation in Israel, these two words might be seen in a different context.
All that aside, the more important context is the one I haven't mentioned: statistics.

Statistics is the backbone of scientific discovery (e.g. the Higgs boson, or its signal, in the data).

The simplest heuristic I have is a fair coin, with a balanced 'result' if I randomise it somehow, so I get a distribution of heads and tails. Ok, say I balance the coin on its edge, what does a fair coin have to say about that?

15

Physics, Astronomy & Cosmology / Cartesian and Polar coordinates

« on: 10/10/2023 03:40:52 »

I think I might have found a youtube vid that explains how polar coordinates are a Hilbert space, if you have vectors with (r,θ) these are orthonormal, hence geometrically perpendicular in the abstract Hilbert vector space.

The video describes how to visualise a transform from polar vector space to Cartesian space. The latter is where we usually define real angles and distances which are not orthogonal, like in the real world. Orthogonality is something that "falls out" of the vector algebra, if you have an inner product defined.

And it explains what Christoffel symbols are in an intuitive way. I'd recommend watching it at least twice; it really gives you a good idea about the metric and why there is one. This is the low-dimensional stuff so it's easy to visualise.

the vid: https://www.youtube.com/watch?v=TvFvL_sMg4g

16

Physics, Astronomy & Cosmology / Weird physics with a guitar string

« on: 06/09/2023 10:51:32 »

I did something a few years ago, ok more than ten years, but I haven't been able to explain it and it isn't a thing on youtube yet.

It involved using an old unwound guitar string in a torsion pendulum. I fixed one end by looping the string through the end bead, around a horizontal pipe and pulling it as tight as possible, the other end was tied in a knot around a piece of steel weighing about 2.5 kg, I actually didn't weigh it or bother with the string's gauge.

I checked the fixed end wasn't rotating by fixing a small piece of sticky tape around the string at the fixed end, so I had a way to see any rotation at that small region, and spinning the weight. I attached more of these small '"flags" along the string so I had about ten or so.

To my surprise, and anyone can try this, some of the little flags started rotating in the opposite direction to the weight, then rotating the same way again. This became more apparent as the weight was spun up then released. I did this over weeks of this thing sitting outside hanging from a steel t-bar, the guitar string never broke.


footnote: I was fortunate that the materials, particularly the weight and how it was shaped, were available. The piece of steel would be recognisable to a scaffolder, it was a flat u-shape with a small length of steel pipe welded to the bottom. I lived with some tradies for a while, in Sandringham.
The other essential is a place to hang it that doesn't disturb the peace too much.

17

Technology / Geeks shall inherit the earth

« on: 21/08/2023 01:39:34 »

A question I have is, what do you think the future will be like for the average person, in terms of how much the technology they use affects what they control, y'know, otherwise?

Will kids be able to dash off an algorithm or two with the help of an AI bot, perhaps for the new IBM quantum computer on the cloud? How many people will be tech savvy, in the sense early amateur radio enthusiasts needed to be?

Will it be the same kind of exclusive club? And how many early ham radio clubs were there in Asia or Africa, what kind of tech-relativity, the West vs the Rest, would you expect in this future?

18

Physics, Astronomy & Cosmology / Talking about Physics

« on: 26/04/2023 02:00:21 »

Hi. I recently had a discussion online about the subject of physics, in which I posted something about simplification, and how that seems to be where physics starts, at least. At the simple end.

A couple of examples are 1) how we can make a large, complicated object like a planet, into a less-complicated 'blob' of matter; since the mass of the planet is the important detail we don't need to know about how the matter is distributed or anything else about it. We can replace the planet with an equivalent mass, theoretically.

Then 2) there's the particle in a rectangular well, a box with infinite potential.
--In electronics you study circuits with ideal elements even though real electronic devices aren't ideal.

And at the really simple end are time and distance. The first, time, is still the subject of debate as to its conceptual existence, or actual physical existence. Distance on the other hand isn't a thing we question very much, although there are theories that suggest the universe is a hologram they are quite complicated, not easy to understand the way we understand distance innately.

If we had a simple explanation for why time and distance appear to be so different, maybe it would all be simple and easy to understand.

But usually you start at the simple end, right? I don't know, perhaps the way momentum starts with a mass and a velocity, but depending on whether you have a relativistic or a quantum context you then have a more complex physical thing. Or do you just have a more complex idea?

p.s. I was asked more than once, in the discussion I mentioned, to define what I thought "physical" means. So I said anything with physical units is physical. I also would say a distance is about as physical as you can get.
You don't erase a distance by measuring it; time on the other hand doesn't seem to work that way.
(?)

19

Physics, Astronomy & Cosmology / How are physical units defined?

« on: 02/08/2022 00:32:22 »

I've been having a stoush with someone recently, about a simple enough thing which is, how physical units are defined.

It seems that, at first we don't bother defining distance, other than in terms of a unit thereof. That is, we just assume that distances are somehow axiomatic. This is clearly not the case when we define units of time; currently defined accurately in terms of a single, 'central' frequency, and the constant speed of light.

But physics doesn't stop and ask, "what really is a unit of distance", or "what is a unit of time", etc. Physics just assumes that units can be defined in terms of each other--speed, in terms of time and distance e.g.--and doesn't bother with the philosophy.

Distance "is what it is"; you measure some and just get on with it. In fact humans measure distances all the time, walking or driving is a 'measurement' of distance; when you move any part of your body it 'moves through' a distance and this constitutes a measurement (of distance). Accurate measurements aren't a rule as such, but are assumed to be a requirement if a theory is being supported by experiments.

Or, why don't we have definitions of time and distance, etc, in other more fundamental terms?

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Physics, Astronomy & Cosmology / Is mass a number?

« on: 29/04/2022 10:00:40 »

This idea is being promoted at another site. I can't make much sense of it.

But I'm wondering if it's true does that mean there's a proof? Isn't it relatively straightforward to prove a number exists?

Or is there a way to prove mass isn't a number? Or do you just accept mass occupies a volume, the same volume some matter is in and forget about proving it?