lpetrich

I've found <a href="http://www.ubka.uni-karlsruhe.de/cgi-bin/psview?document=2001/physik/3&format=1" target="_blank">this rather technical introductory article</a> on the subject, which will probably be impenetrable to anyone not familiar with quantum field theory.

Something that suggests an argument from incredulity against design: a completely benevolent creator would not be willing to design a Universe that requires very arcane mathematics to fully understand, and whose properties can sometimes be very difficult to calculate.

Here are some highlights:

If one extrapolates the elementary-interaction coupling constants up to grand-unified energies, one gets agreement only if supersymmetry is present and one does not have many more particles than expected in the "Minimally Supersymmetric Standard Model" -- otherwise, the extrapolations miss each other.

The agreement is at an energy scale of about 10^15 - 10^16 GeV, which is close to the Planck energy scale of 10^19, where quantum gravity is expected to be strong. That agreement scale is the scale where some Grand Unified Theory (GUT) is expected to have its symmetry broken to the smaller symmetries of the Standard Model.

By comparison, electrons have masses of 5.1*10^-4 GeV and protons and neutrons masss of 0.94 GeV. The most massive elementary particle now known is the top quark, with a mass of 150 GeV.

But we do not see supersymmetry in the known particles; one prediction of it is that every elementary particle has a superpartner differing in spin by 1/2 and having the same mass. But such superpartners are not observed.

So it's expected that supersymmetry is broken, and this breaking forces up the superpartners' masses to a few hundred - thousand GeV (0.1 to 1 TeV). But why does it force up the masses of some particular choices of superpartners?

The supersymmetry-breaking mechanism is not very well understood, so that question is difficult to answer. But one side effect of it is that it sets the mass scale of the familiar non-gravitational elementary particles . But why the observed mass scale and not some other? Such as very close to the GUT-breaking and Planck masses?

Finally, upcoming particle accelerators like CERN's Large Hadron Collider will be able to accelerate their particles to high-enough energies to produce some of these superpartners, and an important Standard-Model particle not yet detected called the "Higgs" -- if they exist. So if everything goes well, we'll be seeing some interesting results over this decade.

Bill

In the minds of the theists, the creator is not bound to create anything that is logically impossible. Thus, if it takes this degree of complexity in order for the creator to design our universe, then the creator is not bound to create a universe of greater simplicity.

Another argument is this one: just who is it to say that it is US (our generation of homo sapiens) who was the intended recipient of the knowledge of how the universe works, anyway? mankind has existed in some form for several million years. Perhaps we have another million or two before we are to reach the point where we have evolved to the point where we finally understand the mind of God well enough to comprehend His creation?

Arguments from incredulity are a last gasp before losing sort of argument in any case.....

== Bill

lpetrich

I meant the Argument from Incredulity as a joke -- just to show that it goes both ways.

lpetrich

I could not help but muse on all the times that some observed complexity has concealed some underlying simplicity.

In our everyday experience, we become acquainted with a large number of substances. But is there any underlying order to them? This has led to a quest for the chemical elements, like the Greek set of earth, air, fire, and water, and the Chinese set of earth, fire, water, wood, and metal. The Greek "elements" are more plausibly identified as states of matter, however, and I can't think of a good interpretation for the Chinese ones.

Eventually, the old Greek elements had to be left behind; the seven metals of antiquity could not be turned into each other, even though they were supposedly mixtures of earth, air, fire, and water. Thus, these substances had to be considered elements.

And the number of recognized elements grew; late in the 18th cy., the great chemist Lavoisier recognized 31 of them, not counting heat and light. And by the middle of the 19th cy., about 30 more were discovered.

Some people toyed with the idea that there are some interrelationships between the element properties; the most successful of these was Dmitri Mendeleyev and his Periodic Table of Elements -- complete with gaps that were eventually filled in with elements discovered later.

Why might this regularity happen? The atomic theory of matter, at first, seemed to give no improvement; 60+ elements accounted for 60+ kinds of atoms. However, atoms were eventually discovered to something other than their name (Greek for "unsplit"), in particular, to be electrons orbiting nuclei. And though the number of known kinds of nuclei would eventually extend into the hundreds, they were discovered to be much tinier than atoms, by a factor of 10^5, thus making most atomic-structure details due to the behavior of the electrons. By comparison, the nuclei only contribute mass and electric charge.

And working out that behavior has resulted in the discipline of quantum chemistry, complete with fairly-successful efforts to compute the properties of atoms and molecules using quantum mechanics and the quantum-mechanical properties of electrons and nuclei.

Having achieved success in finding this underlying simplicity, we now turn to the nuclei. Although many chemical elements have atomic weights that are nearly integer multiples of hydrogen's, some have distinctly non-integer weights, like chlorine (35.3), and some weights are variable (lead from different places). The solution of this conundrum was isotopes, nuclei with different masses that shared the same atomic number (electric charge).

Which were discovered to have atomic weights that were nearly integers. Which hinted at some underlying simplicity. Which turned out to be that they are composed of two kinds of elementary particles with nearly identical masses -- protons and neutrons (nucleons) -- with each isotope having its own number of each.

We have arrived at a new simplicity: there are only four elementary particles, the photon (quantum of electromagnetism), the electron, the proton, and the neutron (I'm omitting gravity for convenience). Or have we?

Beta decays were found to leak energy and angular momentum, two quantities expected to be conserved. The leak was discovered to be a new elementary particle, the neutrino. And combining relativity and quantum mechanics for electrons predicted that electrons will have mirror-image particles with opposite charge. Which were eventually found: positrons or antielectrons. This was eventually discovered for other spin-1/2 particles, like protons, neutrons, and neutrinos.

Although antiparticles are simply some sort of mirror images of ordinary particles, neutrinos were just the beginning of the discovery of a big zoo of elementary particles.

And the large majority of new particles discovered were hadrons, strongly-interacting particles. Trying to work out how they were interrelated was a nightmarish problem, with some theorists proposing that they were all coequally elementary (the "bootstrap model").

In the 1960's, Murray Gell-Mann proposed the quark model; hadrons are composed of either three quarks (proton, neutron, etc.) or a quark and an antiquark (pion, K, etc.). And at that time, from particle-collision experiments, it became evident that nucleons are composite. The "partons" inside turned out to be quarks.

Thus, hadrons, like atoms and nuclei, proved to be composite, being explained by quarks and an additional particle, the gluon. According to one nuclear physicist, "they've turned us all into chemists!"

The result was the Standard Model of particle physics. I will now try to summarize it.

There is an elementary particle with spin 0, the Higgs particle, which has yet to be detected. But it has the unusual property of having a nonzero ground-state field strength, which breaks an elementary-particle symmetry. This nonzero strength then makes the masses of several of the other elementary particles.

There are three photonlike "gauge fields", the gluon (8 of them, with a symmetry called SU(3)), the W (3 of them, with the symmetry SU(2)), and the B (1 of them, with the symmetry U(1)). The Higgs field breaks the W and B symmetry, making two of the W's massive (W+/-, mass 80 GeV), and the third W and B a mixture of a massive state (Z, mass 90 GeV) and a massless one (the photon).

There are several electronlike particles, which come in several "flavors", all with their own masses: six quarks (u: a few*0.001 GeV, d: a few*0.001 GeV, c: 1.5 GeV, s: 0.1 GeV, t: 150 GeV, b: 5 GeV), three electrons (e: 0.0005 GeV, mu: 0.1 GeV, tau: 1.8 GeV), and three neutrinos (tiny but nonzero masses). The u, c, and t quarks have electric charge 2/3 and the d, s, and b quarks have electric charge -1/3; a proton is uud and a neutron is udd (try adding up the charges).

If that starts seeming complicated, then it is not surprising that particle physicists have been searching for some underlying simplicity in the form of a Grand Unified Theory, preferably with supersymmetry. This quest has been successful for atoms, nuclei, and hadrons, and it may someday be successful for the elementary particles.

But I think I'll stop there.

[ May 09, 2002: Message edited by: lpetrich ]</p>

Gooch's dad

lpetrich;

Since neutrons, electrons and protons (the constituents of 'normal matter' all have anti-particle equivalents, can odd types of matter be made from these positrons etc? Using positrons in the outer shells, and anti-partners of neutrons and protons in the nucleus?

I never got far enough in physics to understand that stuff. Quantum optics, not much of that, and that was 15 years ago.

lpetrich

Yes, that is completely possible. In fact, it is an expected consequence of the elementary-particle field equations. And one can deduce from them that turning an ordinary-matter object into its equivalent antimatter one would leave it with many of its properties exactly the same as before, and some of them with reversed sign. In the equations, one reverses the sign of the elementary charge and the sign of the electromagnetic field, and they look exactly the same as before, with the exception of some weak-interaction features, which do need some additional changes.

Thus, a familar object would still have the same size, the same shape, the same color, the same hardness, the same amount of roughness, the same compressibility, etc. Though if it had been electrostatically charged or magnetized when it was converted, the charge or magnetic field would get reversed. If it was radioactive, it would still be radioactive with all decay rates the same, though emitting the antiparticles of the particles that it would otherwise have emitted.

It would be nice if one could make tests of the properties of macroscopic antimatter objects, but there is a grave difficulty: having it coexist with ordinary-matter objects. Matter-antimatter annihilation works on a particle-by-particle basis, not a macroscopic-object-by-macroscopic-object basis; the result will be a giant fireball -- a gram of antimatter will combine with a gram of its surroundings to release two grams of energy, about as much as released by a 40-kiloton nuclear bomb.

However, several such tests have been done at the elementary-particle level, and have been successful to the accuracy of the measurements, which is sometimes very great.