From Ptolemy to Dark Matter - Part 1
Feb 04, 2009

One such assumption that shapes our accepted view of the Universe is that gravity dominates the motion of galaxies.

It is difficult to change these types of fundamental belief systems. For example, in the time of the Hellenic astronomer Claudius Ptolemaeus, it was a widely held fundamental assumption that the Earth was the center of the cosmos. In fact, there were many good reasons to believe it. The stars, the sun, and the planets visibly move across the sky and the Earth obviously feels very solid and fixed.

According to the best thinkers at the time, the heavenly bodies were positioned on invisible spheres with as many as five spheres per planet. By allowing for spheres within spheres, one could explain the retrograde movement of the planets. To its credit, much was explained with this world-view. With Ptolemy’s sophisticated use of epicycles, deferents, and the innovative introduction of the equant, the Ptolemaic system was very successful at predicting such things as the precession of equinoxes as well as planetary motion (more so than the Copernican system when it was first developed).

However, by the sixteenth century, Galileo’s observations of the phases of Venus were completely incompatible with the Ptolemaic system. Subsequently, Kepler’s prediction of the transit of Venus in 1631 was a great success for the heliocentric, Copernican view of the solar system.

Not to be unnecessarily provocative, but there are interesting similarities between the Ptolemaic paradigm and the current theories surrounding Dark Matter and galaxies. Just as there were good reasons to believe in invisible celestial spheres driving a Geocentric Model, there are reasons to believe in invisible spheres (called “haloes”) of dark matter surrounding galaxies.

It all has to do with how the mass of a galaxy is measured. One popular approach to compute galactic mass is the orbital method. In the orbital method, the rotational velocity of stars (the red shift of radio waves from hydrogen gas around the stars) is used to infer the mass of the galaxy. The math is relatively straightforward: once the stellar orbital velocity (or “velocity dispersion” for the galaxy) and the distance from the center of the galaxy that contains the mass in question are measured, then it is easy to solve for mass. However, the math only includes gravity as the potential energy source for the system.

The problem that begets dark matter is as follows. When the mass of a galaxy with this gravity-only approach is derived, there is more computed mass than visible matter. That is, the sum of the mass of all the stars and visible dust in the galaxy is far less than the mass derived with the Orbital Method. If gravity drives the rotational velocity of the stars in the galaxy, then there must be hidden mass in the form of invisible dark matter. What if gravity is not the dominant force driving the rotational velocity of galaxies?

Today, asking this question is like asking a learned astronomer in 1550, “What if the Earth is not at the center of the cosmos?” Asserting that gravity is not a dominant dynamical force in the motion of galaxies is just as shocking to astronomers of our current time. However, there is good evidence that supports the notion that electromagnetic forces in plasma act on the cosmological scale.

Hannes Alfven (Nobel Laureate for his work in plasma physics), proposed that galaxies reside in immense, gyrating, Birkeland currents that convert large-scale electromagnetic forces into rotational energy in a galactic system. In turn, leakage currents in the galaxy are converted into rotational energy in star systems. Seminal work by Anthony Peratt (e.g. see Snell and Peratt, 1995) has shown that the flat rotational curve of galaxies is well modeled by plasma simulations without the need for dark matter. All the observations of the galactic core, the intense X-rays, gamma rays and rotational energies could be explained with sufficient current densities driving the galactic system (Peratt, 1986).

The typical flat rotational velocity curve of a galaxy does not indicate hidden dark matter mass, it indicates that another force is at work. This is why deriving the mass of a galaxy using equations that only include gravity as the source of potential energy leads to problems. Additional electromagnetic forces are at work that drive the galaxy like an electric homopolar motor (see a summary in Donald Scott’s book “The Electric Sky”).

To be continued.

Contributed by Thomas Wilson