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Latest comment by angryphysicist

angryphysicist Says:

May 17th, 2007 at 12:42 pm

“But then, just sometimes, some radical thinking in science happens to work.”

History tends to disagree with this. The track record for “radical thinking” is notoriously bad…worse than the track record for economists’ empirical predictions being valid! (And *that* is saying something!)

The problem is that no one really remembers the “radical” off-the-wall theories *because they were wrong.* Who remembers Tesla’s dynamical gravity? No one, because General Relativity was: 1) the more cautious solution, 2) actually was a theory that existed (Tesla’s theory, as far as I know, was largely nonexistent).

Everything Einstein did was cautious and conservative; Brownian motion combined the well accepted realms of mechanics and thermodynamics, the Photoelectric effect involved thermodynamics and electrodynamics, and Special Relativity involved mechanics and electrodynamics. All of them were extremely cautious and conservative moves.

Actually, I’m flipping through the appendices in Rovelli’s book “Quantum Gravity”, and in appendix C1 he covers this discussion quite well.

May 18th, 2007 at 10:59 pm

RB: I’m not really well read in Tesla’s work, only loosely familiar with some of it. It seems, to say the very least, impressive! I cannot comment really anymore than that unfortunately.

Carlbrannen: I suppose it’s my inner purist general relativist speaking, but I don’t really have a problem with the tensor notation. Index gymnastics should be approached more as a game than a chore

You are right though about the orbits, it can be done without the tensor notation *sometimes*; there are sometimes when it can’t be done without it but perhaps that’s my inner general relativist speaking again.

May 20th, 2007 at 8:29 pm

Andrew Daw Says:

“Surely not, history of physics and science in general tells us that if it wasn’t for ideas that were highly radical in their time (eg those of Copernicus, Gallileo, Newton, Darwin, Lavoisier, Pasteur, Planck, Einstein etc) there would have been no progress at all in understanding how the natural world is the way that it is. ”

But all of these people’s “radical” thoughts were based off of empirical findings, not off of pure speculation like what is happening today.

Copernicus’ big discovery was that the empirical findings of Kepler et al. did not work with the geocentric model of his times; instead it worked with heliocentric model.

Galileo found by rolling balls of different masses down a curved incline that the rate at which the bodies fell was not linked to their masses, contrary to the popular Aristotlean theory. He figured it out empirically not through “pure reason” alone as modern theorists are doing now.

The same goes for Darwin, Planck, Einstein, and others.

Was it challenging for their times? Yeah, of course; but it was, in my humble opinion, a different sort of “radical thinking” than what is being done today by “pure reason” alone. They actually used empiricism whereas an appallingly large number of theoretical physicists do not anymore; which is rather depressing.

Pioneer1 Says:

“Pysicists routinely set G = 1 = 0.0000006. In a field where 1 = 0.0000006 or anything physicists want it to be there can be no science. Numbers in physics are corrupted.”

Um, G isn’t a number, it’s a constant with different values in different scale systems. The MKS system has it at about (2/3)*10^-10 m^3 kg^-1 s^-2, the CGS system has it off by a margin of 10 or so. The Planck scale has it at one planck volume per planck mass times planck time squared ().

There’s nothing really “corrupt” about it, it’s just a different scale that is computationally simpler to work with.

“Einstein equations is a definition. You cannot use ‘Einstein equations’ in any calculations.”

Why is it a definition and not an equation? What makes it a definition as opposed to an equation?

“When there are infinite solutions for the equations those equations cannot give a valid description of the world.”

What about an eigenvalue problem? There are an infinite solutions to:

d^{2} f(x)/dx^{2} = -f(x).

For example, f(x)=e^{ix}, or a constant nonzero multiple of it (there are thus an infinite number of solutions to the equation).

One could say “Yes, this is all very well and fine, but it is not a physics equation!” It’s the geometrized form of the (time-independent) Schrodinger equation.

May 20th, 2007 at 9:28 pm

Woops, I missed this one:

“What is the connection between tensor notation and the orbits? I don’t think NASA uses tensors to compute orbits. All you need is period and radius of the orbit.”

By “orbits” I assume you mean Newtonian paths? Because things are little more complicated than “just” the period and radius of the orbits (largely because things like “position” can become a nonlocal entity…worse, one doesn’t really speak about “position” insomuch as one takes about “the time it takes according to a nuclear clock for radiation to reach a location and come back to the observer”).

It doesn’t really matter if you use “tensor notation” or not…it’s merely a notation (actually, I believe the Cartan formalism is used, but I could be mistaken).

Frankly I don’t think it’s really efficient to be attacking the notation, since if you present it without the tensor notation you haven’t really changed anything at all. (Actually, it may be worse be tensors transform in a specific manner with coordinate transformations, which is great with something like General Relativity.) It’s a mere storm in a teacup.

When doing numerical calculations to solve the Einstein field equations with Fortran, e.g., you don’t really have much of a choice in the matter…the calculation “is equivalent” to using tensor notation. It’s just how you present the answer (whether you present them as 10 independent equations or as a matrix)…which is then presentable in tensor notation…

I suppose one could use the weak field approximations for all practical purposes…I would imagine that’s what NASA really does since they are working in the weak field!

May 21st, 2007 at 8:27 pm

“G is a defined unit, just like foot or meter. Would you say that meter is a constant of nature?”

Well, the meter is an abstraction created by humans to ease measurements.

The gravitational constant was discovered rather than invented; if I recall correctly Henry Cavendish discovered it and announced it in his work Philosophical Transactions back in 1798.

“But G is not a constant of nature, it is a defined unit. G is simply the proportionality constant in Kepler’s rule.”

Actually, G is a constant of nature. It is equal to for the Planck length , the Planck time , and the Planck mass .

May 25th, 2007 at 6:20 pm

May 27th, 2007 at 2:07 pm

Well, you define a rational unit as:

“One of the quantities is kept constant in order to measure other quantities with it.”

Suppose you had a ruler, and it had some length say a meter. Suppose you want to measure your own height with it, then the length of your ruler is kept constant in order to measure other quantities with it; so a meter (the length of the ruler) is a “rational unit”.

But a conventional unit as:

“The rational unit is expressed by scaling it with a conventional unit, such as meter.”

Which is pragmatically what we did with the rational unit. Perhaps here you mean like say a kilometer is a “conventional unit” since it’s 1000 meters long, and a meter is the “rational unit” that’s scaled? (I don’t know, I’m trying to guess an example of a “rational unit” versus a “conventional unit”.)

But then this seems like an arbitrary and pointless definition.

That’s just my take on it from first glance, it seems to be a sort of false dichotomy.

May 31st, 2007 at 12:52 am

Physicists look at A and say it is a constant of nature because it stays invariant under unit transformations. Does this make sense?

Then I fail to see how any arbitrary length is not a constant of nature as when one changes the units one measures with it is the same length.

There is more to a thing being a constant of nature than “invariance under transformations”…that’s what makes a thing a tensor

June 2nd, 2007 at 12:22 pm

But Pioneer, there is a fundamental difference between a quantity invariant under coordinate reparametrizations and constants of nature.

It seems by your scrutiny, a “Constant of Nature” is undefinable. Indeed you admitted previously that “My personal opinion is that a ‘constant of nature’ is an artifact of the system of units.”

Well, what do you mean by this?

Suppose a constant of nature X exists. Would that mean that it can only be determined through experiment, or through some a priori mathematical manipulations? If it’s the latter and it’s expressed in one set of units, would that change the fact that we have a “new” constant of nature X’? Why does it suddenly change with a change of units?

“But how do physicists derive G? I believe that G is not derived from measurements but it is defined.”

Could you elaborate? Physicists just randomly pick a value for “G” that works?

I did a simple google search and came up with a number of experiments that can derive the experimental value of G:

Some of these you could probably do at home

June 4th, 2007 at 8:25 pm

Pioneer, you never even defined what a constant of nature is…as a matter of fact, if memory serves, you refused to do so.

Your entire argument seems to be sophistry, which is the source of John’s frustration (frankly I’m surprised he stayed with you as long as he did).

Actually, it reminds me quite a bit of Hegelian psychobabble…”the antithesis of an axiom is an anti-axiom which has the resulting synthesis of Truth not to be confused with truth, as Truth is a person but not an individual nor is it alive but it’s not dead…blah blah blah. Ah but we haven’t defined what an axiom is! So I can redefine it thus, tacitly, and still claim the high ground!”

It’s little more than intellectual masturbation. I think it was Karl Marx who once said “The philosophers have only interpreted the world. The point however is to change it.” Your word games, which by the by is pure idealism that Wittgenstein laid to waste long ago, is little more than a mediocre attempt to interpret the world…no offense.

June 6th, 2007 at 5:57 pm

Pioneer

If I am reading your argument correctly, you said that if it is a definition then it is not a constant of nature.

No, what I am saying is that you are using the phrase “constant of nature” and you are refusing to define it.

You wish me to identify your use of sophistry? Well, since you apparently are misusing the term to refer to a historical group of philosophers, which is the incorrect context of its use (I’m using it in the modern sense of the word: sophistry makes heavy use of specious arguments in order to deceive someone).

Where have you used linguistic sleight-of-hand, you might ask; your definition of “conventional units” and so forth is evidence enough of it.

Wittgenstein remarked that if something could be said meaningfully in one language, it could be said in any language. But your argument cannot even be presented in English, much less French or any other language one would like.

It seems to suggest sloppy thinking. Indeed the shroud of mystery that makes “constants of nature” so seemingly “deep” a discussion is because we cannot meaningfully talk to you about it, you haven’t even defined or referred to what you mean by “constant of nature”!

You have not given any criteria for what a constant of nature is. You seem to allege that the constants of nature “don’t exist” because they use units…but since you haven’t even defined what a constant of nature is it doesn’t matter.

You appear to have a vague “inkling” of what a “constant of nature” is, but you don’t really have any well defined criteria for identifying a “constant of nature”. Without this, there’s nothing to attack.

It’s pure linguistic “sleight-of-hand”, and sophistry not even at its best.

Now, perhaps if you could mirror the mathematicians and start with a few definitions (like “constant of nature” which you repeatedly refuse to define), and then present structured logical arguments, maybe just maybe you’ll either convince someone or you’ll realize a mistake in your argument.

But your technique of presenting specious arguments is rather unappealing, and your linguistic sleight-of-hand doubly so.

June 22, 2007

Pioneer, you do realize that force is a classical explanation that is openly described as a mere approximation to the underlying quantum phenomena, right…?

Because it seems that your, uhm, criticism of force is entirely irrelevant to everything.