exchemist

I did - spot of sunstroke from the fine weather here in Brittany where I am on holiday…..

What bothers me is why the unit of charge on the electron is 1/3 or 2/3 that of the electron. Suggests something odd or missing in our theories. But off-topic for this thread, I suppose. What has this to do with the fine structure constant?

Lousy time to pull this stunt when we’ve all just seen what happens when regulatory corners are cut in a safety-critical industry.

Yes I started on this but changed my mind, thinking it made things too much in one go. But indeed, let's see what he has to say. My guess is he'll divert away onto something that dodges actual experimentation. But I'll be happy to be proved wrong.

You can't just airily dismiss particle physics as "voodoo". The determination of all these constants relies on it. You see, in physics, all these things fit together. Maxwell's equations are a c.19th theory that has been explained in the c.20th by virtue of the twin discoveries of relativity and quantum theory. To give you a simple example of this interlinking, Einstein's famous mass-energy equivalence relation E=mc² is a special case of his more general relation E² = (mc²)² + (pc)², in which p is momentum. If p=0, i.e. a system at rest relative to the observer, this reduces to E=mc², which we can observe for instance in the mass and energy balance of nuclear reactions. But for light, consisting of photons with zero rest mass, that term is zero and we are left instead with E=pc. If you apply de Broglie's relation, p=h/λ (from quantum mechanics) to that (λ being the wavelength), and note the relation between speed, wavelength and frequency,ν, for any wave, c=νλ, you get E= hc/(c/ν), i.e. E=hν, which is Planck's relation for the way the energy of a photon depends on its frequency. So that is more evidence that SR, which is where Einstein's formula comes from, is correct and that the invariance of c, which is what SR is all founded upon, is also sound. So it is all interlinked, each piece supports the rest and all the elements have been tested by observation. Your final comment about particle accelerators shows you still don't get it. Sure, the equipment is stationary in the lab (relative to the observers) but the particles whizzing along inside are moving, relative to that frame, at close to the speed of light. So what they experience, from their frame of reference, is a lab - with its coils carrying a current of moving charges and thus a magnetic field, whizzing past them at close to light speed. This in fact is one way to observe the time dilation predicted by SR. Particles that are unstable and have a known decay lifetime, as measured at rest, are found to have longer lifetimes when whizzing along very fast in this way. And the degree to which this happens is as SR predicts. SR wins again!

In your scenario of one wire moving relative to the other, the extra motion will alter the current flow as seen from the other reference frame and this will affect the magnetic field experienced in each frame. But this can be allowed for without altering the value of μ₀ in the calculation. In fact, the joke is that the whole phenomenon of magnetism arises precisely due to relativity, i.e. how an electric field in one frame appears from the viewpoint of another that is moving relative to it. Further reading here: https://en.wikipedia.org/wiki/Relativistic_electromagnetism

Universal? I'm not sure what that means and it's not what I said. I said μ₀ is a constant. @swansont has explained to you what that means. I also said that nothing in physics says μ₀ is frame-dependent. Look, if μ₀ were frame-dependent, then relativistically moving particles in magnetic fields, e.g. in particle accelerators, would behave respond to the field differently from prediction as their velocities through it changed. So far as I am aware (I'm open to correction from the real physicists here ) that is not a feature of particle physics. And indeed, as @MigL has observed, if it were to be frame-dependent, than ε₀ would also need to alter in the opposite sense such that the observed invariance of c is maintained. Because that is where we start from. I know you keep arguing that the invariance of c can't really be observed, but that's because you have steadfastly refused to consider the observational evidence for that, in spite of my attempts to get you to do so.

Others have pointed out your misunderstanding of the concept of force and of what F=ma means. As for “circular logic”, I reiterate my basic point that c is observed to be invariant, so that is an input number to all these formulae, not an output. You have not shown the magnetic constant is not a constant. And you have no basis for describing the charge on the electron or Planck’s constant as “dubious”, when your ignorance of the simplest physics is painfully apparent in this thread. You don’t even know how units work. I’m sure everyone here is enthusiastic about helping you learn, but for goodness sake don’t claim modern physics is “wrong”, given your current level of understanding. That is just farcical, frankly.

I’m familiar with de Broglie’s relation. What’s a de Broglie bound?

Ah I see. So sonar can be used to transmit text. Interesting.

That’s odd. They looked like tyre tracks to me. Is there so little going on in that yard? I’m inclined to think it’s not so much a hoax as a bunch of credulous true believers putting 2 and 2 together and getting 5.75.

But what I want to understand is how can they “lose contact” when that’s what happens anyway as soon as they submerge?

Sadly this is now also a feature of another forum I subscribe to. But I agree. The notion that shoving the ads in your face, when you are in the middle of following a train of discussion, will make you come under the influence and buy something, seems absurd to the point of offensive. However I feel sure the response will be that it's a feature of the site software that's considered essential to the moneymaking side of the site. As they say in The Right Stuff, "Know what makes this bird go up? Funding makes this bird go up." So it may be a price we users have to pay.

What "contact" was lost? I thought radio didn't work under water.

Sure but the image is effectively split into an infinite series of images, one for each wavelength, is it not? So it does involve splitting into colours. That's why its full name is "chromatic" aberration, surely?

I've told you how μ₀ is measured, the most modern being via measuring α, the fine structure constant and then applying the values of the charge on the electron e, Planck's constant h, and the speed of light c, by mean of the relation μ₀ = 2αh/e²c. This is all done in the lab and does not need to involve relativity. Acceleration does not come into it. The units of μ₀ are N/A², i.e. force/current squared, which falls out of the formula. α itself, i.e. the thing being measured, is dimensionless. You say "therefore light speed is relative to the frame" but this firstly does not follow and secondly it is contrary to observation, namely that the speed of light is not relative to the frame of reference. You seem to me to be looking at this from the wrong end of the telescope. This being science, it starts from the observations and then derives theories consistent with them. c is found by observation to be invariant and not frame dependent. So that is what we start from, not where we end up by some derivation or other. So it's pointless futzing around with formulae containing c and trying to show that it can't be constant, due to some claimed frame-dependence of one or more quantities in a formula, when experiment says otherwise.

This is nonsense. So long as observer and the observed phenomenon are all in the same frame of reference, you don't need to concern yourself at all with the issue of reference frames. There is no "relative motion between frames" when you measure μ₀, or Sommerfeld's constant (the fine structure constant), α. Everything is in the same lab, including the observer, and the phenomena observed in the making of the measurements do not involve relativistic effects. Nothing in physics says that μ₀ is frame-dependent. You appear to be making this up, in a forlorn attempt to pick holes in relativity, without understanding what μ₀ is.

You have misunderstood this. The magnetic constant is still regarded as, er, a constant. The distinction is that it is now treated as measured rather than defined. But it is still a constant. It makes little sense saying it is frame-dependent, as it is measured via a pair of parallel wires in the same frame as the observer, or alternatively derived from measuring the fine structure constant (via quantum phenomena, again measured in the same frame as the observer) and applying defined values of the electron charge and Planck’s constant.

Good, so we are agreed we can forget the “simulation” stuff. I would not use the term “intelligent design” for what is really just the well-known “fine tuning” argument for God. That argument is older than ID and, unlike ID, is intellectually honest, though I am not convinced by it. Though I wouldn’t be surprised if the ID people have adopted it, now that their own pseudoscience has been so thoroughly discredited. I suspect the reason the fine structure constant intrigues people more than other apparently arbitrary constants of nature, say the values of magnetic permeability or electric permittivity of the vacuum, or indeed Planck’s constant, is that it is dimensionless, i.e. just a number.

In this Wiki article: https://en.wikipedia.org/wiki/Vacuum_permittivity there is a formula that plugs in the relevant values of the quantities and shows the relation between them. It's important to use consistent units. There are some notes showing equivalent ways of expressing the units.

Well I think Sabine is spot-on, as far as science goes. The whole notion of simulation is firstly untestable, so it's metaphysics, not science, and secondly it immediately demands the question: " Simulated by who, or what, and to what end?" It's God by another name, basically - just more IT nerdy, and therefore more hip and trendy. I'm not impressed by Tyson. For a start he dismisses philosophy as a waste of time, which shows a lack of understanding of the foundations of his own subject, (details here: https://scientiasalon.wordpress.com/2014/05/12/neil-degrasse-tyson-and-the-value-of-philosophy/ ) and then, that stated point of view notwithstanding, he starts indulging in metaphysical speculation himself! (I have not watched the video, as I find videos a very inefficient way of communicating information. If you can link a write-up of the ideas, I might read that.)

What equation are you working from?

No. It’s just a number. Every physical constant has to have a value. This “simulation” stuff seems to be just an IT nerd’s version of the “fine tuning” argument for God, which I have never found persuasive.

I hadn't heard about the prostate. What does milk do to it? As a 69yr old man, I have an interest in this.

That was going to be De Sanity Clause I think. But he seems to be proving so uncharismatic and unpleasant that he's not gaining the traction he hoped, even though aping TFG at every turn. By the way, "TFG" always makes me laugh. I instinctively think it means either That F***ing Guy or The Fat Guy, though actually I gather it doesn't stand for either. Suppose if it were the latter then Chris "Zeppelin" Christie would have to be (TFG)².