Astronomers have discovered a planet that has three suns, something that was long thought to be impossible. (Astronomers argued that the orbits would be too unstable.) Can a planet in a figure eight orbit be far behind?

MOND, the acronym for MOdified Newtonian Dynamics is a theory put forth by Moti Milgrom in 1983 to resolve problems with galaxy kinematics without resorting to dark matter. The theory decouples inertial and gravitational mass (breaking the equivalence principle) positing that at very small accelerations (those below an observationally determined constant a₀), the gravitation force felt by a body is actually smaller than the force predicted by the famous Newtonian equation F = ma. Aside from the bizzare nature of the change, the theory has several things going for it, not the least of which is that it made predictions that were later verified (namely the existence of low surface brightness galaxies).

Another point in its favor is that it can explain the Pioneer anomoly. When I first heard of the theory and the problems it was meant to solve, I thought that the theory was crazy, but that it might just be crazy enough to be true. I even bandied about the idea of writing a popular science book about it which itself would have several things going for it:

• MOND could actually be correct – such a book would be early to the game
• While there are many science popularization books written, there certainly aren’t many speculative hard science popularizations written – unless you count all the string theory stuff – it could jump start a whole category!

Some final food for thought; I haven’t done the calculation myself, but apparently constant acceleration at a₀ for our best guess at the age of the universe produces a velocity of – wait for it – the speed of light. I don’t know if this new world would be cool enough for Walt to have to put on shades before he glanced at it, but quite a few textbooks would need to be rewritten

And some MOND links:

• The MOND pages
• Dr Dark Matter

The Pioneer 10 and 11 spacecraft have experienced an unexplained drag that has caused them to travel slower than predicted, a phenomenon known as the Pioneer anomaly. Attempts to explain it using normal physics have failed, which leads people to speculate that it will require brand-new physical theories to explain. I personally hope that this is like the discovery of radioactivity by Roentgen in 1895 — a first initial glimpse into a new world.

Despite the fact that in theory it is entirely reducible to quantum mechanics, chemists do not have a mathematical model of water molecules that completely explains its behavior.

Update. Sigfpe has more thoughts at his blog.

The Standard Model is the name particle physicists give to their unified theory of electromagnetism, and the weak and strong nuclear forces. The Standard Model is an example of a gauge theory (unrelated to the gauge integral). Gauge theories are parametrized by Lie groups. Particles in gauge theories possess internal state that does not correspond to a classical observable; this internal state is described by an element in the Lie group. The group for the Standard Model is U(1) x SU(2) x SU(3).

This is a subject that I’ve always meant to learn more about, but I’ve never had the chance. Gauge theories make the subject of Lie algebra representations more vivid. For example, the part of the Standard Model that describes hadrons (particles such as protons and neutrons) is SU(3). SU(3) was found by fitting the existing hadron data to an 8-dimensional representation of the Lie algebra su(3). The 8-dimensional representation is not the smallest possible representation of su(3); there is (pretty obviously) a 3-dimensional representation. Taking that representation seriously led to the discovery of quarks.

Here are a few survey articles about the Standard Model from ArXiv:

• Standard Model
• Quantum ChromoDynamics
• Phenomenological guide to physics beyond the Standard Model

The three body problem in physics is the study of the trajectories of three bodies mutually attracted by (Newtonian) gravity. Unlike the two body problem, the three body problem cannot be solved in general, but some specific solutions are known. An article in the Notices of the AMS reports that a new (well, new circa 2001) solution has been found where all three bodies travel in the same orbit — a figure eight.

The figure eight orbit is stable, which means that it is robust under small perturbations. Since any actual physical system will be perturbed slightly by the gravitational pull of other bodies, stability is a prerequisite for a solution to actually be found in nature. So the figure eight orbit may someday be observed by astronomers.

Last week Slashdot linked to an article on Physicsweb that reports on an experiment at the Institute of Theoretical Physics to create superstrings in the lab.

I finally found a chance to look at the original article on ArXiv, and Physicsweb’s article turns out to be misleading. The proposed experiment would simulate a superstring, not actually create one. This is a perfectly legitimate idea, but condensed matter physics is the Tinkertoys of quantum mechanics: you can build almost anything. A simulation of a superstring is a long way away from showing that superstrings really exist.

Scientists are at the Stanford Linear Accelerator Center (SLAC) are using a particle accelerator to help recover a lost work by Archimedes. The Archimedes Palimpsest is a parchment book that once contained copies of Archimedes’ works, but was later erased to be reused as a prayer book. The palimpsest contains the only copy of Method of Mathematical Theorems and only copy of On Floating Bodies in the original Greek.

SLAC’s website also has a press release about the current state of research into the existence of the pentaquark, a theoretical particle made up of five quarks (all known particles made up of quarks only take two or three). The verdict? Not proven.