Physics with some relations to Astronomy...

(last updates: 4. Jun/31. Dec 2000, look there)

An own neutrino article   [27. Apr 2001]
Vom 25. Feb 2000: ein Neutrinovortrag von mir   [aktualisiert und erweitert am 27. Aug 2001]

The following remarks and most links are destined for physicists or other well informed people with scientific interests. Only the first link below is also interesting for aesthetical reasons and therefore no experts only site.

For I'm myself a physicist, I want to put a few remarks first. The most fundamental questions in physics nowadays are related with elementary particles and the unification of all forces between these.

Since the 70's there has been absolutely no real theoretical advance. At that time Salam and Weinberg derived the unification of electromagnetic and weak interactions into one generalized force, which holds its uniqueness at energies of around 100 MeV and more and distances of 10-18  m and less. Following this success were numerous attempts to unify this interaction with the strong (nuclear related) force.

But these trials gained up to day no convincing results: besides the theory is not unique by theoretical aspects, the most widespread versions are already falsified by experiments, which showed no verifiable proton decays, setting a lower limit for the half life time of this nucleon. And so the simplest model symmetry SU(5) is along with a number of compelling ones already excluded. It's simply not known, if these attempts will succeed anyway in the way followed in the last decades.

Even worse is the situation with gravity: not only nobody knows now really, how to unite it with the other interactions, we know on the other side there are really intrinsic problems with it (General Relativity) and the non-gravitational, but relativistic quantum field theories. For example the effects for an infalling observer near the principal reachable singularity at the center of black holes are beyond our proved theories and even more the first 10-25 s and less pose great problems for these theories, which work well at other conditions.

Finally we are waiting for any type of breakthrough, and I personally doubt heavily, that the current trials heading in different directions will deliver any usable results. What we lack, is a new idea. For example, the open question of General Relativity, the cosmological constant, raises further questions: what is it's value - and why has it the value it has? The answer may come from a theory we not know until yet (Quantum Field Theory delivers no acceptable value so far).

Not so far away we even not know with absolute certainty, if neutrinos have a rest mass. This rest mass - now considered as probable - can have big consequences for elementary particle Physics and also for Astronomy.


Here follow some links to mainly principal questions, but the first is also to enjoy the beauty of a natural phenomenon.

 

ray traced image of an auroraThe Aurora Page
 
The particle stream originating in our sun and general referred to as solar wind interacts strongly with the magnetic field of the planets of our solar system which feature such a field. Around one million tons of particles are send into space in every second by our sun, and for example the Voyager probes showed giant aurora phenomenons in the Jovian atmosphere. In the same way as the charged particles, trapped in the magnetic field of the planet, enter in high latitudes the atmosphere of Jupiter, they do it on our planet and the others with a magnetic field.

From high latitudes on Earth the classical Aurora can be observed (of course only in the so-called polar winter). It's the region where the field converges and carries charged particles into the atmosphere, there inciting luminous phenomenos in the upper part of it: the molecules (and atoms) of the air take the energy from the incoming particles and enlight often great parts of the (night) heaven.

These Auroras are feeble and the low brightness poses difficulties to photograph them. Best viewed they are with the human eye, which can adapt to a wide variety of illuminations. But this fine homepage offers nonetheless a number of excellent pictures of the Aurora. Besides further links to related sites there are explanations of the observed effects, predictions of activities (especially interesting for people in high latitudes of course, but it is true, that even at locations like Hawaii there can be seen - eventually one time in a century - at rare oppurtunities some of them.

As a final remark, the solar activity plays a major role in the strength of the Aurora and the now fast rising activity (maximum is expected for 1999 or 2000)  will cause more and stronger Auroras than at the average.
 

General Physics Site

A very comprehensive site with news, links to physical societies etc., which already won a number of awards. From there you should be able, to get most interesting actual informations, for example also standard frameworks from CODATA and others are listed.
 

2 Particle Physics Sites: popular   expert
 
The first one is more for generally particle physics interested people and available in several languages, while the second one is for experts, mainly an electronic journal for physicists working on these high energy topics --- also some astrophysical and cosmological topics are discussed. Both are good main sources for the interested anyway.

Life, the Universe and the Electron
 
More informations about one of the most important elementary particles.

Deutsche Seite über Quarks
 
Im Grenzbereich der (Teilchen-)Physik verschwimmt die Unterscheidung zwischen teilbar und unteilbar bezüglich kleiner Teilchen...

 

John Bahcalls homepage
 
He is a multiple decorated, leading specialist for Solar Astrophysics and neutrinos. If you don't know the connection of the two, consider the following.

The only star we can precisely scrutinize by physical standards so far is our sun. Besides the direct measurement of electromagnetic waves, which originate in the photosphere and above and deliver therefore no direct hints about the solar interior. Alternative with surface wide Doppler measurements the helioseismology is performed, which allows similar as the earthquake measurements by identifying acustic waves derivation of parameters of the Sun even in central regions - better than simple flux measurements and similar methods but it's also an indirect way.

The only method to get direct evidence of the nuclear fusion reactions in the Suns core up to now is counting the neutrinos produced in these reactions. But since decades we know, that there arise new problems.

First of all, the neutrinos are the least well scrutinized particles, whose existence is proved, so far. Second, exact solar models require cross section knowledges and plasma features in an environment, which can not exactly reproduced in our laboratories.

The major problem now is a big discrepancy between the neutrinos, which should be produced in the Sun according astrophysis and nuclear physics, and the measured ones in different ranges of energy.

Astophysical it seems unlikely, that there are major faults in the calculations, for the models describe well the properties of star clusters, where many results of the models can be verified.

Probably the elusive neutrinos have to do with this difference. It seems now, that they have a tiny rest mass and therefore are responsible by some sort of change between different types of neutrinos.

But this complex has to be solved precisely in future - and you will gain all relevant information at Bahcalls homepage.
 

The Ultimate Neutrino Page
 
A quit comprehensive site with many numbers about the elusive particles. A good way, to gain another overview about the hot topic of physical investigation.
 

GALLEX official signGALLEX experiment/GNO
 
Here the results of the leading solar neutrino experiment are presented, which are conducted by an European colloboration. Besides other things, you could download a 1.3 MByte postscript file which contains a good paper about the neutrino complex for the interested. Despite being from 1997, this is a good state description. Now the GALLEX experiment is transformed into GNO, which is planned to increase from 30 to 100 tons of gallium content and to run for at least one further decade. These pages are obviously now under redesign and you should await the adaptation to the GNO successor.
 

SNO logo Sudbury Neutrino Observatory (SNO)

This is a new type of neutrino observatory, which exploits the Cherenkov radiation to detect all types of neutrinos, and not only electron neutrinos like the chemical experiments at Homestake (Chlorine), GALLEX or SAGE (Gallium). There are good prospects for a big leap in the theory regarding the neutrino properties. In June 1999 the first two neutrinos were already observed. Watch out for the measurements to come.
 

Borexino logo BOREXINO homepage

The possibly most ambitious neutrino experiment so far: it tries to detect low energy neutrinos in real time (remember, that the chemical experiments "only" sum up events for certain time spans). It relies on the neutrino scattering by electrons and is therefore also sensitive for different neutrino flavors. Full operational state should be achieved at the end of 1999.


 

Kamioka: two neutrino detectors
 
These are the two Japanese neutrino detectors, which are no chemical experiments but feature an even higer energy limit due to the utilized reactions. Look regularly at this site, because these ongoing experiments produce results faster than the long time chemical experiments. The two are mostly named "Kamiokande" and "Super-Kamiokande".

 

SAA logoSAA - another neutrino site
 
Another site about neutrinos with a more general content. There is among others also some work of the well-known Fermilab presented.

 

GSI logo: acceleratorsGSI homepage
 
This German site - presented almost entirely in English - is the internet vehicle of the famous "Gesellschaft für Schwerionenforschung" in Darmstadt, Germany. There are the most of the so-called transurane elements produced by violent nuclear reactions of colliding heavy ion nuclei. For this purpose and other studies like highly excited nuclear states and generation of radiation as an - beside others - medical application.

 

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