Thursday, February 22, 2007

Photons Behind Bars, Busting Loose


Quantum mechanics teaches us that light has both wave and particle qualities. For decades Niels Bohr's Complementarity Principle was thought to prevent the wave and particle qualities of light from being measured simultaneously. Recently physicist Shahriar Afshar proved this wrong with a very simple experiment. As a reward, the physics community attacked everything from Afshar's religion to his ethnicity. Prevented from publishing a paper, even on arxiv, he "went public" to NEW SCIENTIST magazine.

Afshar's apparatus is based upon the familiar two-slit experiment. Because of the wave nature of light, beams passing through Pinhole 1 and Pinhole 2 form an interference pattern of light and dark fringes. Here Afshar put light behind bars, adding a grid corresponding to the null (dark) fringes. Behind this he placed a lens to refocus the light onto photon detectors.

Because the bars correspond to null fringes, no light is lost in passing through. The photon count at the far end is exactly the number of photons going in. This demonstrates both wave and particle nature of light in a single experiment. This doesn't necessarily conflict with quantum mechanics, but it does prove Bohr's interpretation wrong.

Despite the simplicity and importance of Afshar's experiment, or maybe because of it, he was treated too poorly to describe. Where have we seen behaviour like that? It could have been worse--he could have been female. Afshar's paper will finally be published in Foundations of Physics.

Old theories about light are bound to change. For decades teachers would tell us to shut up, the speed of photons is flat, like the Earth. There is still huge resistance to a changing speed of light. Now look how far we have come!

New Scientist's cover features "DARK ENERGY: It's the Biggest Mystery in the Universe." At one time repulsive energy was thought to solve many problems, even providing support to inflation. This would lead to more respect and funding for physicists. As Lawrence Krauss and others agree, the repulsive energy hypothesis is falling apart. Now the big brains are at a complete loss.

"That honeymoon period is now well and truly over. Although dark energy is a ubiquitous term in cosmological conversations, no one actually knows what it is. As (Rocky) Kolb says, 'Naming is not explaining.'

"Although there are plenty of tentative explanations, each one seems to suffer from some fatal flaw. The simplest of the solutions on offer is the so-called cosmological constant...unfortunately physicists are having trouble finding a way to fit a cosmological constant into their best existing theories.

"A small non-zero dark energy is more difficult to explain than zero," says Sean Carroll, "so we are driven to wilder ideas...dark energy could be the ether of the 21st century."

As readers know, a simple equation like GM = tc^3 solves the problem precisely, without any hypothetical energies. It also provides a successor to inflation. It makes predictions about the speed of light, the CMB, the 4.507034% of baryons and many other things. Finding the answer to a problem is very, very satisfying.

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3 Comments:

Blogger nige said...

Hi Louise,

For decades Niels Bohr's Complementarity Principle was thought to prevent the wave and particle qualities of light from being measured simultaneously. Recently physicist Shahriar Afshar proved this wrong with a very simple experiment. As a reward, the physics community attacked everything from Afshar's religion to his ethnicity. Prevented from publishing a paper, even on arxiv, he "went public" to NEW SCIENTIST magazine.

Bohr's Complementary and Correspondence Principles are just religion, they're not based on evidence.

The experimental evidence is that Maxwell's empirical equations are valid apart from vacuum effects which appear close to electrons, where the electric field is above the pair-production threshold of about 10^18 v/m.

This is clear even in Dyson's Advanced Quantum Mechanics. There is a physical mechanism - pair production - which causes chaotic phenomena above the IR cutoff, that is within a radius of approx. 10^{-15} m from a unit electric charge like an electron.

Beyond that range, the field is far simpler (better described by classical physics), because the field doesn't have enough energy to create loops of particles from the Dirac sea.

What Bohr tries to do is to freeze the understanding of quantum theory at the 1927 Solvay Congress level, which is unethical.

Bohr went wrong with his classical theory of the atom in 1917 or so.

Rutherford wrote to Bohr asking a question like "how do the electrons know when to stop when they reach the ground state (i.e., who don't they carry on spiralling into the nucleus, radiating more and more energy as Maxwell's light model suggests)?"

Bohr should have had the sense to investigate whether radiation continues. We know from Yang-Mills theory and the Feynman diagrams that electric force results from virtual (gauge boson) photon exchanges between charges!!!!

What is occurring is that Bohr ignored the multibody effects of radiation whereby every atom and spinning charge is radiating! All charges are radiating, or else they wouldn't have electric charge! (Yang-Mills theory.)

Let the normal rate of exchange of energy (emission and reception per electron) be X watts. When an electron in an excited state radiates a real photon, it is radiating at a rate exceeding X.

As it radiates, it loses energy and falls to the ground state where it reaches equilibrium, with emission and reception of gauge boson radiant power equal to X.

I did a rough calculation of the transition time at http://cosmicvariance.com/2006/11/01/after-reading-a-childs-guide-to-modern-physics/#comment-131020

Once you know that the Yang-Mills theory suggests electric and other forces are due to exchange of radiation, you know why there is a ground state (i.e., why the electron doesn’t go converting its kinetic energy into radiation, and spiral into the hydrogen nucleus).

The ground state energy level is the Yang-Mills corresponds to the equilibrium power the electron has radiate which balances the reception of Yang-Mills radiation with the emission of energy.

The way Bohr should have analysed this was to first calculate the radiative power of an electron in the ground state using its acceleration, which is a = (v^2)/x. Here x = 5.29*10^{-11} m (see http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/hydr.html ) and the value of v is only c.alpha = c/137.

Thus the appropriate (non-relativistic) radiation formula to use is: power P = (e^2)(a^2)/(6*Pi*Permittivity*c^3), where e is electron charge. The ground state hydrogen electron has an astronomical centripetal acceleration of a = 9.06*10^{22} m/s^2 and a radiative power of P = 4.68*10^{-8} Watts.

That is the precise amount of background Yang-Mills power being received by electrons in order for the ground state of hydrogen to exist. The historic analogy for this concept is Prevost’s 1792 idea that constant temperature doesn’t correspond to no radiation of heat, but instead corresponds to a steady equilibrium (as much power radiated per second as received per second). This replaced the old Bohr-like Phlogiston and Caloric philosophies with two separate real, physical mechanisms for heat: radiation exchange and kinetic theory. (Of course, the Yang-Mills radiation determines charge and force-fields, not temperature, and the exchange bosons are not to be confused with photons of thermal radiation.)

Although P = 4.68*10^{-8} Watts sounds small, remember that it is the power of just a single electron in orbit in the ground state, and when the electron undergoes a transition, the photon carries very little energy, so the equilibrium quickly establishes itself: the real photon of heat or light (a discontinuity or oscillation in the normally uniform Yang-Mills exchange progess) is emitted in a very small time!

Take a photon of red light, which has a frequency of 4.5*10^{14} Hz. By Planck’s law, E = hf = 3.0*10^{-19} Joules. Hence the time taken for an electron with a ground state power of P = 4.68*10^{-8} to emit a photon of red light in falling back to the ground state from a suitably excited state will be only on the order of E/P = (3.0*10^{-19})/(4.68*10^{-8}) = 3.4*10^{-12} second.

This agrees with the known facts. So the quantum theory of light is compatible with classical Maxwellian theory!

Now we come to the nature of a light photon and the effects of spatial transverse extent: path integrals.

‘Light ... "smells" the neighboring paths around it, and uses a small core of nearby space. (In the same way, a mirror has to have enough size to reflect normally: if the mirror is too small for the core of nearby paths, the light scatters in many directions, no matter where you put the mirror.)’

- Feynman, QED, Penguin, 1990, page 54.

That's the double-slit experiment, etc. The explanation behind it is a flaw in Maxwell's electromagnetic wave illustration:

http://www.edumedia-sciences.com/a185_l2-transverse-electromagnetic-wave.html

The problem with the illustration is that the photon goes forward with the electric (E) and magnetic (B) fields orthagonal to both the direction of propagation and to each other, but with the two phases of electric field (positive and negative) behind one another.

That way can't work, because the magnetic field curls don't cancel one another's infinite self inductance.

First of all, the illustration is a plot of E, B versus propagation dimension, say the X dimension. So it is one dimensional (E and B depict field strengths, not distances in Z and Y dimensions!).

The problem is that for the photon to propagate, the two different curls of the magnetic field (one way in the positive electric field half cycle, the other way in the negative electric field half cycle) must partly cancel one another to prevent the photon having infinite self inductance: this is similar to the problem of sending a propagating pulse of electric energy into a single wire.

It doesn't work: the wire radiates, the pulse dies out quickly. (This is only useful for antennas.)

To send a propagating pulse of energy, a logic step, in an electrical system, you need two conductors forming a transmission line. In a Maxwellian photon, there can be no cancellation of infinite inductance from each opposing magnetic curl, because each is behind or in front of the other. Because fields only travel at the speed of light, and the whole photon is moving ahead with that speed, there can be no influence of each half cycle of a light photon upon the other half cycle.

I've illustrated this here:

photon

If you look at Maxwell's equations, they describe hoe cyclically a varying electric field induces a "displacement current" in the vacuum which in tren creates a magnetic field curling around the current, and so on. They don't explain the dynamics of the photon or light wave in detail.

One thing that's interesting about it is this: electromagnetic fields are composed of exchange radiation according to Yang-Mills quantum field theory.

The photon is composed of electromagnetic fields according to Maxwell's theory.

Hence, the photon is composed of electromagnetic fields which in turn are composed of gauge bosons exchange radiation. The photon is a disturbance in the existing field of exchange radiation between the charges in the universe. The apparently cancelled electromagnetic field you get when you pass two logic steps with opposite potentials through each other in a transmission line, is not true cancellation since although you get zero electric field (and zero electrical resistance, as Dr David S. Walton showed!) while those pulses overlap, their individual electric fields re-emerge when they have passed through one another.

So if you are some distance from an atom, the "neutral" electric field is not the absence of any field, but the superposition of two fields. (The background "cancelled" electromagnetic field is probably the cause of gravitation, as Lunsford's unification suggests; I've done a calculation of this here (top post).)

Aspect's "entanglement" seems to be due to wavefunction collapse error in quantum mechanics, as Dr Thomas S. Love has showed: the when you take a measurement on a steady state system like an atom, you need to switch over the mathematical model you are using from the time-independent to the time-dependent Schroedinger equations, because your measurement causes a perturbation to the state of the system (e.g., your probing electron upsets the state of the atom, causing a time-dependent effect). This switch over in equations causes "wavefunction collapse", it is not a real physical phenomenon travelling instantly! This is the perfect example of confusing a mathematical model with reality.

Aspects experimental results show that the polarizations of the same-source photons do correlate. All this means is that the measurement paradox doesn't apply to photons. A photon is moving at light speed, so it doesn't have any internal time whatsoever (unlike electrons!). Something which is frozen in time like a photon, can't change state. To change the nature of the photon it has to be absorbed and re-emitted, as in the case of Compton scattering.

Electrons can have their state changed by being measured, since they aren't going at light speed. Time only halts for things going at speed c.

So Heisenberg's uncertainty principle should strictly apply to measuring electron spins as Einstein, Polansky, and Rosen suggested in the Physical Review in 1935, but it shouldn't apply to photons. It's the lack of physical dynamics in modern physics which creates such confusion. The mathematician who lacks physical mechanisms is in fairyland, and drags down too many experimental physicists and others who believe the metaphysical (non-mechanistic) interpretations of the theory. That's why string theory and other unconnected-to-any-experimental-fact drivel flourishes.

10:15 AM  
Blogger nige said...

Sorry, the link to the photon illustration above should be http://thumbsnap.com/v/CW93pyt3.jpg

10:32 AM  
Blogger nige said...

[Although you might naively expect the classical Maxwellian radiation emission rate to be greatest in the ground state, you need also take account of the effect of electron spin changes on the radiation emission rate in the full analysis; see 'An Electronic Universe, Part 2', Electronics World, April 2003. I will try to put a detailed paper about this effect on the internet soon.]

10:37 PM  

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