Open questions in Physics

Open Questions in Physics (a work in progress)

Here is a list of stuff I find remarkable. These are issues that are honest mysteries which should be worrying for each and every physicist. All of these are acknowledged unsolved problems but for one reason or another, we tend to turn a blind eye to them.

Only issues which have been published several peer-reviewed journals are mentioned here. This is not 'shady science'.

Tiny unexplained gravitational effect on space probes launched

When we measure the speeds of Pioneer 10, Pioneer 11, Odyssee and some other space probes, we find that they consistently don't quite adhere to the known laws of gravity by a tiny amount, (8.74*10±1.33)^-10m/s².

Discovered by NASA, JPL and Los Alamos National Laboratory, which have been studying this over the past 15 years without finding an explanation.

The main people behind this, John D. Anderson (JPL), Michael Martin Nieto (LANL) and Slava G. Turyshev (JPL) officially hope that they will find an easy explanation for this anomalous sunward acceleration, but also propose to launch a space mission to more properly research this phenomenon.

The Aerospace Corporation. 1998.
Los Alamos National Laboratory. 1998.
Paper in Physics Review Letters. 1998. This is one of the original papers.
Paper in Pysics Review D. 2001. Very lengthy, 54 pages refuting lots of possible conventional explanations.

General Relativity and Quantum Theory flatly contradicting eachother

Currently we hold both GR and QT to be valid theories, describing the world as we know it. However, these are not only different theories, they stem from very different premises. It is impossible for both of them to be true at the same time. Currently this only actually leads to problems when predicting stuff that is moving really fast and is really tiny at the same time but the fundamental problem is far larger.

FIXME: needs links

Missing mass of the universe

This is a big one. In various ways, we can 'weigh the universe'. On a smaller scale, we can weigh planets by studying the motions of any moons they may have, or determine the mass of the sun by measuring the orbits of planets.

When we do this for the entire universe, and several ways are available, we get a figure. If we then count the amount of matter we see, we find that a staggering 95% is missing.

Because saying that you can't find 95% sounds bad, the discussion has been reworded into the study of 'dark matter' - it isn't missing, we just can't see it right now. The magnitude of the problem can accurately be gauged by the fanciness of the theories proposed to explain this dark matter, which needs to be 20 times more prevalent than the 'light matter' we see:

Invisible dark mini-galaxies
Neutrinos in incredible numbers which each have a tiny mass
WIMPS: Weakly Interacting Massive Particles. Very special massive invisible elementary particles, so far conveniently undiscovered
Revival of Einstein's Cosmological Constant, renamed ' vacuum energy'.
Giving the space-time continuum itself a mass!

This discussion is very open and nowhere near being solved. Renaming 'the missing mass problem' to 'Dark Matter Research' hasn't helped. No credible theories are available right now, mostly for lack of evidence. By its very nature, dark matter must be pretty hard to spot!

March 31 2003 UPDATE: The results are in! And they are even weirder than previously thought. 4% of matter consists of atoms we can see, 23% is 'Cold Dark Matter' and a staggering 73% is proposed to be the even more elusive 'Dark Energy', which is rapidly being renamed to 'Phantom Energy'.

Solar Neutrino Discussion

Neutrinos are produced in nuclear reactions which power the Sun. Our theories on the operation of the sun predict how many neutrinos we should see, but so far, we don't see enough of them.

The two obvious solutions to this problem are that the sun works differently or that the neutrinos disappear before we can measure them.

The debate has raged since 1962. Currently we believe that while travelling from the sun to the earth, part of the neutrinos 'oscillate' into a variety we cannot detect.

This oscillation however means that the neutrino has suddenly acquired a mass which, even when tiny, has huge consequences. In short, if neutrinos have mass, they don't travel at the speed of light anymore. However, in the SN1987a supernova, the neutrinos arrived 18 hours before the photons. This in itself does not prove anything but it certainly does not prove that neutrinos move slower than light.

High temperature superconductivity

Low temperature superconductivity is explained pretty well in a 1957 publication by John Bardeen, Leon N. Cooper, and J. Robert Schrieffer, known as the BCS theory, for which they were awarded the 1972 Nobel prize. The idea is that two electrons gang together to form a de facto boson which, like the bosonic photon, is transparent to other bosons and can thus travel without resistance.

In 1986 high-temperature superconductivity was discovered (leading to an uprecedentedly quick 1987 Nobel prize) for which the BCS theory does not hold - at higher temperatures the so-called Cooper pair boson cannot normally form.

There are literally thousands of theories on how high temperature superconductivity would work but none of these are definite and many of them are more like agglomerations of a number of ideas which put together give the right answers - but not a sense of explanation.

Physicsweb 'Can phonons help explain high-temperature superconductivity?'. 2001.
Science Express (website of Science Magazine): 'Important clues to an explanation of high temperature superconductivity'. 2002. Max Planck Institute, Centre d'Energie Atomique in France and at the Russian Academy of Sciences research that provides 'clues'. A good quote: 'High temperature superconductors have been known for 15 years and are already being used in a variety of technological applications. However, the mechanism responsible for this phenomenon has thus far remained elusive.'.

Many will claim that high temperature superconductivity is explained but as of late 2004, this is simply not true.