zztop

On 2/23/2017 at 7:45 AM, foxsboris.naumov1994 said:

 

Well here is the answer SNIP gave me: this can easily be done with determinants. If a square matrix's determinant does not equal zero, then that square matrix will have an inverse hence having a unique solution. Since this is a 2x2 matrix, just compute the determinant with the condition that it cannot equal zero:

(1)(2)-(2ab) =/= 0

2 =/= 2ab

1=/= ab

 

Did you look at the post just above yours?

zztop.

I thought that an infinite speed of gravity was mainstream,

No, it isn't.

And Van Flandern's idea that gravity had a speed of no less than 20 billion c is also to my mind not contrary to mainstream's infinite speed.

It is full fledged crackpot. Stop posting rubbish.

 

In general relativity, gravity isn't really a force, it's just the bending of space time. So I guess, in a sense, he would say zero force. Someone correct me if I'm wrong.

 

 

 

I actually think he's asking a different question.

 

I think he's asking something like this:

If a mass appeared out of nowhere, how long would it take for it to bend all of space?

I would guess instantly because it is mechanical. The same way that moving the end of a 1 light year long stick would be instantenous, instead of taking 1 light year.

 

Based on his quoting the Van Flandern crank, he's asking exactly what I answered to.

BTW: if the Sun disappeared instantly, the effects on Earth would be felt 8.5 minutes AFTER its "disappearance".

The obverse: if another "Sun" appeared instantly, next to the current Sun, its effects would be felt on Earth....8.5 minutes after its "appearance".

 

I reckon that the speed is Van Flandern's more than 20 billion c.

Some say the speed of light, c (eg LIGO's Gravitational Waves).

Some say instantaneous at all distances, ie even at infinity.

Some say instantaneous, but only locally, not at infinity.

 

 

Please stop quoting cranks, the speed of gravity is "c".

Wow now that's impressive! Can you reveal how it works, or is that a dumb question?

Here is a good synopsis.

zztop.

What is the news on Reg Cahill??

I see that he is now Emeritus. He must have retired (70yrs). But he still has a phone & office it seems.

I wonder what a free-range Reg Cahill will do. Lots of youtube, lots of seminars.

He has been retired by the faculty. Due to being an (in)famous crank.

Strange.

Yes, i have read that Maxwell was the key to Einstein's foray into the STR.

I have also read -- Maxwell's Original Equations -- by Tombe -- 2011 -- especially page 5.

 

Yes, Newton believed that light was corpuscular, ie that it wasn't a wave.

But his beliefs re light had nothing to do with his beliefs re gravity, quite the contrary.

Tombe is yet another internet crank, it is time you stopped.

We have an infinite (thin)(flat) plate.

1. Newton is standing on the plate. Does he feel a g-force?

2. Einstein is standing on the plate. Does he feel a g-force?

3. madmac is standing on the plate. Does he feel a g-force (madmac is an aetherist).

 

And, are these three g-forces (a) zero, or (b) mansized, or (c ) very large, or (d) infinite?

 

I have my own ideas re the theoretical answers. But i am interested in other's ideas.

Yes, they all feel [latex]F=2 \pi G \rho m[/latex]. Read here. It is a standard exercise given in intro to physics.

 

Imagine if Tesla's work had spawned a desire for small generators capable of powering electrical appliances for a single home, or block of apartments, or perhaps a neighborhood unit of multiple private homes. I think if we'd suspected, in Tesla and Edison's time, how much we'd depend on electricity every day, we might have been more protective of the ability to create our own.

According to the excellent video posted by "arc", the initial implementation by Edison DID have "local" power plants. In this age of cyber-terrorism it makes perfect sense to move away from central power plants and from distribution grids.

Re measuring or estimating fringe shifts. M&M used a yellow sodium light for alignment etc,

...because monochromatic light has a much shorter coherence length than white light. One needs short coherence light in order to calibrate the setup (make the arms have equal length).

but then a white acetylene light for the tests. Acetylene gave a nice big sharp black central main fringe, which they reckoned allowed measurements of 1/100th of a fringe.

Only AFTER MM calibrated the setup, they could afford to use white light since the long coherence length can no longer affect the measurement. White light had the advantage of making very sharp fringes with a very distinct central fringe.

But Pearce & Grusenick's green HeNe laser often gives fuzzy fringes (at least on the youtube video).

...which only make the fringes harder to read.

This would make green M&Ms more difficult.

ONLY if one were naive enough to use eyeballing in order to determine fringe "move".

Which reminds me, i think it was Hicks who pointed out that eyeballing the fringe shifts would give different results to photographic measurements (believe it or not).

...which is precisely why eyeballing is not used in modern MMX.

Currently (no pun intended), sure. If a significant number of people become users of DC current, expect a market for DC appliances to start opening up to take more efficient advantage.

Agreed, since all solar "power plants" come with their own inverters in order to be able to pump the energy back into the AC grid.

 

It's more than just Betamax vs VCR marketing. DC current has its advantages. AC has a lot of versatility, but only when considered as a grid. It's actually pretty difficult/costly to match the phase between grids. If you don't have a grid in the first place, a lot of the advantages disappear. Transforming voltage up and down more easily is still one of ACs big advantages, but lower voltage requirements, less danger, and longer appliance life are very tempting.

 

But my real point was more of a mindset. What if the right to control energy utilization personally had become as important to many as the right to bear arms? I would argue that perhaps, in the modern US, being in control of the power sources that run virtually everything important in your life is much more important than having guns to defend yourself. Or perhaps we need the guns because others can shut off our power?

Your point is about to get a lot stronger with the advent of solar energy. In effect solar panels constitute a "personal" power plant. They produce DC current which, unfortunately, needs to be transformed (at significant energy loss) into AC because of the fact that the appliances can only work off AC.

This means that [latex]IR - BLv = 0[/latex], right? So the velocity would be [latex]v = \frac{IR}{BL}[/latex]?

For the current I just need to replace the [latex]v[/latex] I just found in [latex]i = \frac{BLv}{R}[/latex].

 

Not exactly: [latex]G - BLv = 0[/latex]

The sum of the two forces is zero at equilibrium, right?

Yes. Meaning that [latex]i[/latex] must be 0.

Thank you very much for the help!

There is one more thing to consider: at equilibrium, the em induced voltage [latex]-BLv[/latex] will cancel out the battery voltage [latex]G[/latex] so, the speed [latex]v[/latex] is ....? And the current [latex]I[/latex] in the wires becomes....? And the Ampere and Lorentz forces become equal to...?

Oh right! Because the current on stick is the same but flowing on the opposite direction of the one where there is the battery. Because of this, they push each other, but only the stick can move, so it moves far from the battery, right?

Correct.

Do I have to sum this one with the Lorentz force? Does this mean that the direction of the Lorentz force is contrary to the Ampère force?

Yes, the Lorentz force is [latex]\vec{F_L}=L\vec{I}X\vec{B}[/latex] and it opposes the Ampere force. The absolute value of the Lorentz force is [latex]F_L=LIB[/latex]

And does this mean that the Ampère force gradually decrease until it equals the Lorentz force? Is it a that point that the velocity is constant? And it's a that point that I have to calculate the current with the formula I gave in the initial post, right?

Yes.

The magnetic field [latex]B[/latex] is the one that causes the conductor to move, right? The Ampère's force law is, in general, given by this expression:

[latex]\vec F = \frac{\mu_0 I_1 I_2}{2 \pi r} \vec r[/latex]

But here I have only one current. How does this work?

The Lorentz force is given by [latex]\vec F = q \vec v \times \vec B[/latex] and it's direction should be perpendicular to the magnetic field [latex]B[/latex], so moving along the binaries like the arrow shows in the picture. Am I right?

You have TWO currents , of equal absolute value and OPPOSITE senses.

The exercise says this:

A metal stick of mass [latex]m[/latex] and length [latex]L[/latex], initial still, can slide on two long horizontal binaries without friction. A uniform vertical magnetic field is present in the region in which the stick can move. The battery [latex]G[/latex] applies a constant electromotive force [latex]\epsilon[/latex] to the circuit formed by the binaries and the stick, letting flow a current which direction is showed in the figure. Demonstrate that the velocity of the stick approaches a constant value [latex]v[/latex] and determine the module and the direction of it. What is the current that flows in the stick when this value is reached?

Exercise 3.jpg

 

So, we know there's an electromotive force produced by the battery G. Let's call it [latex]\epsilon_G[/latex]. There is then another electromotive force produced by the magnetic field in which the circuit is placed. Let's call it [latex]\epsilon_B[/latex].

This last one can be found with the Faraday-Neumann Law this way:

[latex]\epsilon_B = - \frac{d \Phi (\vec B)}{dt}[/latex]

where the [latex]\Phi (\vec B)[/latex] is the magnetic flux found this way:

[latex]\Phi (\vec B) = \vec B \cdot d\vec S[/latex]

After a couple of passages, I arrive at this:

[latex]\epsilon_B = -BLv[/latex]

Correct, so far.

Now, what causes the conductor to move and in what direction will it move? There is a force, called Ampere force....What is its direction, what is its expression?

There is another force that RESISTS the move of the conductor. It is called the Lorentz force. What is its direction and expression? Do the two forces cancel each other?

This is extremely disappointing considering that I contributed nearly 100 items to his list.

 

While the phrasing there could be better, I disagree that the physics FAQ there is "very poorly phrased". This concerns a fundamental point of SR, directly related with the topic at hand. The simultaneity convention is just that, a convention. Choose another convention and you "make" the speed of light anisotropic in your rest frame. You do not need to assume the light speed to be isotropic wrt your system of reference; it's merely convenient to do so.

 

Therefore, Einstein rephrased the second postulate as follows in 1907 (emphasis mine):

 

"We [...] assume that the clocks can be adjusted in such a way that the propagation velocity of every light ray in vacuum - measured by

means of these clocks - becomes everywhere equal to a universal constant c, provided that the coordinate system is not accelerated."

- http://www.soso.ch/wissen/hist/SRT/E-1907.pdf

Correction: it is the COORDINATE-dependent speed of light that "becomes anisotropic". PROPER speed of light is isotropic (and equal to "c" in vacuum).

PROPER light speed in a uniformly accelerated system as well as in a uniformly rotating system is also isotropic and equal to "c".

In other news , the Flinders University finally unloaded the Cahill embarrassment. They finally got the crank out.

With emphasis mine:

 

 

Not just "mainstream" but a simple fact: experiments that clearly use a one-way light path and find isotropy are inherently unable to rule out a large class of theories in which the one-way speed of light is anisotropic

- http://math.ucr.edu/home/baez/physics/Relativity/SR/experiments.html#one-way_tests

 

( Yes I'm back )

 

While that may be true, it's up to us to demonstrate that by means of scientific arguments. Mud throwing is particularly unscientific.

PS I read: "In 2010 the Telesio - Galilei Academy of Science awarded Professor Reg Cahill a Gold Medal for the development of Process Physics. The ceremony was held at the University of Pecs, Hungary."

- http://www.flinders.edu.au/science_engineering/caps/staff-postgrads/info/cahill-r/process-physics/

 

Not bad for a "crank"!

Sigh

The remark from the John Baez website is very poorly phrased. The class of theories he's talking about is the class of "test theories" "

-Edwards

-Robertson-Mansouri-Sexl

-Standard Model Extension

By virtue of being test theories, they inherently must ASSUME that light speed is anisotropic and they assign a set of parameters in order to model the said anisotropy. Experiments constrain these parameters to values that disprove the initial assumption of anisotropy.

As to Reg Cahill, a quick look at his publications and at "

 

http://imgur.com/a/xIydC

The answers is b) ab≠1, but I have no clue how to get to that answer... Can someone help me?

 

Hint: the determinant of the system must not be zero

Tr

I'm taking an engineering intro class, and this problem has me stuck:

 

"Vector R in Fig. 4.9 is the difference between vectors T and S. If S is inclined at 28 degrees from the vertical and the angle between S and T is 32 degrees, calculate the magnitude and direction of vector R. The magnitude of S and T are 19 cm and 36 cm, respectively. " Fig. 4.9 Is simply three lines pointing diagonally downward from the top right, with R being horizotal, T below R, and S below T (sorry, I cant find a picture to upload). I only have pre-calc under my belt (no physics) but I feel like this shouldn't be to hard to understand. I'm just finding it impossible to figure out HOW to solve this. I have access to the answer:(R = 18.8 cms, direction is horizontal) but I really need to know how to do it. Any help is greatly appreciated. Thanks

Triangle cosine rule teaches us that:

[latex]R^2=S^2+T^2-2S*T*cos x[/latex]

where x is the angle between S and T.

I'll let you figure why R is horizontal

zztop.

No i am correct. Hammar merely showed that there is not entrainment by aether.

 

Extending this to supposedly proving that there is no aether or no aether-wind is Sfarti's silly idea.

Most of the wordage & equations & ideas in that article in that link are Sfarti's, not Hammar's.

Of course you are "correct", you never give up in your nonsense.

I don't think I've addressed the issues in the OP, just the misconceptions peripheral to it, so this is moot. Crap arguments provide no support for whatever claims you make.

+1. I give up. When one plays with crap one gets dirty.

zztop.

I looked into Hammar a couple of weeks ago after u or someone else here referred to his test.

His test was simply to find any evidence of aether-drag -- one leg of a sort of M&M gizmo was inside a thick steel tube, the other leg was out in the air.

He found no evidence to support drag. This proved that Michelson's & Miller's ideas about aether-drag were wrong.

In other words, aether, if it exists, suffers or enjoys little or zero drag.

 

I don't remember seeing anything wrong with Hammar's test & logic etc. However i only read what was little more than a super-long abstract, less than one page. I suppose that he did write a multi-page paper, which i wouldn't mind reading.

You have a very poor understanding of Hammar's experiment. Read here

zztop.

But a 60dg angle off ideal must have seemed acceptable to them. 90dg off ideal would give a null result. It wasn't till later years that they realised that the aether-wind was almost perpendicular to the Equator, & that ideally they should be doing tests in the Tropics.

Total rubbish. Disproved 82 years ago by Hammar experiment.