Forums before death by AOL, social media and spammers... "We can't have nice things"
|    sci.physics.research    |    Current physics research. (Moderated)    |    17,516 messages    |
[   << oldest   |   < older   |   list   |   newer >   |   newest >>   ]
|    Message 15,589 of 17,516    |
|    John Heath to Roland Franzius    |
|    Re: How to measure a Lorentz contraction    |
|    08 Mar 17 08:09:19    |
      From: heathjohn2@gmail.com              On Sunday, March 5, 2017 at 2:55:56 AM UTC-5, Roland Franzius wrote:       > Am 03.03.2017 um 10:04 schrieb John Heath:       > > I like it. Simple and do-able. Should       > > be able to swing a 3 foot wire at 3 or       > > 4 Hz by hand with the hand end of the       > > wire clamped to a scope. I have spectrum       > > lab audio analyzer software on a lap top       > > for VLF whistlers , moving sky charges.       > > With this most of what is needed is already       > > in place. As you have already done this I       > > can proceed with confidence. One concern.       > > Standing in the middle of no where spinning       > > a 3 foot wire while looking at a lap top could       > > draw unwanted attention. I am tested for       > > a better WIFI connection officer , that's       > > my story and I am sticking to it.       > >       > > As to your dislike of the Lorentz contraction       > > interpretation of magnetism you are not alone.       > > I can say from my shoes it grows on you       > > over time. How often is there an opportunity       > > to toss a fundamental force in nature such       > > as magnetism straight into the trash bin?       > > One less to worry about.       > >       >       >       > Don't, because there are genuine electric and magnetic fields.       >       > The two quadratic forms E^2-B^2 and E.B are invariant with respect to       > Lorenz transformations. E.B=0 and |E|=|B| is mainly radiation.       >       > So there are static fields with |E|>|B| which are predominantly electric       > fields because you can find a system of reference with B'=0 and E' =       > E/sqrt(1-(v/c)^2).       > This system can be thought to be the rest system where you see charges       > at rest producing their common Coulomb field.       >       > And there are predominantly magnetic fields |B|>|E| where you can find a       > system reference with E'= 0 and B' = B/sqrt(1-(v/c)^2)       >       > Taken cum grano salis of course, because E,B are components of a rank 2       > tensor field, transforming with the product of two Lorentz tranformation       > matrices.       >       > An example of pure magnetic field with E=0 everywhere is the cylindrical=       >       > magnetic field B_phi =1/r around a finite conducting wire with with two       > equal constant currents: one of the negative charges to the left and       > positive charges to the right of identical current and charge density.       >       > So as an experiment, move at constant speed with your synchronized       > clocks/meterstick/ampere-meter/volt-meter equipment along a wire with       > the half velocity v/2 of the electron current.       >       > Now you have two equal currents of negative electrons and positive ions       > with equal but opposite velocities +-v/2.       >       > The wire is assumed somehow to be electrical neutral in the rest system       > of the ions.       >       > Of course, there will be a small longitudinal electrical field E_z to       > drive the electric current against the resistivity and to supply by ExB       > the dissipation energy current density from the field outside into the       > wire.       >       > E_z and dissipation can be made very small or even zero for a       > superconductor. So we can neglect the dissipation problem in a first       > approximation.       >       > Now you have by the Lorenz formula       >       > B'_phi = B_phi /Sqrt(1-(v/2c)^2)       >       > and       >       > E'_r = v/(2c) x B_phi / Sqrt(1-(v/2c)^2)       >       > which means that in this system the current is larger and the wire is       > not neutral but - as an ideal conductor - carries some surface charge       > density D_r that, by definition, is the value of D_r at the surface.       >       > How does this happen?       >       > Lorentz contraction contracts the longitudinal measured distance of the       > ions from rest at v=0 to v/2 using the simultaneity of the moving       > clocks. By the same argument the distance of electrons is enlarged       > because their velocity is reduced from v to v/2. So the net charge       > density varies linearly with v.       >       > This fundamental effect arises at velocities as small as the current       > velocity of electrons of order 10^-11 lightseconds/second for a current       > of 1 A at a density of some 10^27 m^-3.       >       > The gigantic particle density of charges moving freely in metallic       > conductors makes these macroscopic effects easily detectable and       > measureable with high precision. This simple fact enabled Gau=DF, Faraday       > Maxwell and Einstein to find the laws of electrodynamics.       > These laws, applied by the gauge of the 4-momentum, imply Lorentz       > invariance of all physical laws.       >       > --       >       > Roland Franzius              Yes there is B=0 E=1 such as a Van De Graaff generator. There       is also B=1 E=0 such as a magnet. I will give an example in       applied physics where the same magnet is B=0 E=1.              This experiment requires a budget of 20 dollars plus a cleared       kitchen table. 1 old school small black and white TV set from       a thrift shop , 5 to 10 bucks , and a strong flat coin type       magnet from a hobby shop 10 to 15 bucks. We now have our       electron particle accelerator , TV , with a phosphor screen       to collect electron trajectory data. Electron velocity is in       the neighborhood of .1 c for a accelerating element of 10 KV       for this type of TV. Place the north end of the magnet facing       the TV screen. You will note the screen raster will turn       clockwise , Maxwell is right. Place the south pole and the       screen will turn counter clockwise , Maxwell is still right.       So far we have B=1 E=0. However if you look closely at the       magnet from the side you will see a black spot. A spot where       electrons with a velocity of .1 c are not hitting the phosphor?       Turning the magnet around will not help as there will still be       a black spot that electron do not care for. A Coulomb force to       cause this would have to be in the range of 15 KV to stop an       electron at .1 c in its tracks. That coulomb force is not in       Maxwell's equations. However it is in the Lorentz contraction       interpretation where effective movement of electrons only in       a magnet will result in a negative Coulomb force. This makes       it B=0 E=1 for a magnet.              Interesting though. If it were a anti matter magnet then it       would be the positrons that are effectively moving therefore       a strong positive Coulomb force. The black spot would now be       brighter than the rest of the screen. Now that I think of it       the screen plus a 10 city block radius around the screen would       light up. Maybe moving protons to make the positive magnet       would be better.              --- SoupGate-Win32 v1.05        * Origin: you cannot sedate... all the things you hate (1:229/2)    |
[   << oldest   |   < older   |   list   |   newer >   |   newest >>   ]
(c) 1994, bbs@darkrealms.ca