Spiral Galaxies as a Creationist Clock

By Mike Janssen

In the controversy over the age of the earth (and the universe), there are several unresolved questions and problems. One such (general) problem deals with galactic structure in a spiral galaxy. In this problem, physical evidence shows a nice spiral structure in the Milky Way Galaxy, as well as the M51 "whirlpool" galaxy, among others. In addition, stars close to the respective galactic centers orbit around the center (in a fashion similar to the way a planet orbits a star) much faster than stars near the edge of the galaxy. Thus, the "nice" spiral structure evident in these galaxies should not exist after one or two rotations - a period of a few hundred million years - this implies that something is not as it seems (Humphreys 2005). Either there is some sort of matter that is unaccounted for, or the galaxy has not been around long enough to lose its structure. However, this claim can be explained using conventional scientific models. First, however, one must understand the claim and its implications.

rotational velocity of the galaxy

Figure 1 - The predicted (A) and observed (B) rotation curve of a galaxy (the orbital velocity as a function of distance from the center of a galaxy).

Humphreys suggests that "galaxies wind themselves up too fast". He points out that the observed rotation speeds of stars around the galactic centers of spiral galaxies are so fast that, if the universe was more than a few hundred million years old, it would be a "featureless disc of stars" instead of the spiral shape that we know today. In terms of the "natural clock" notion, Humphreys proposes that the initial state of the system is the spiral shape of galaxies such as the Milky Way, and the final state of the system should be when the galaxy collapses into a "featureless disc of stars". As far as scientific knowledge is aware, this is an irreversible process, with a "time of usefulness" of a few hundred million years. The problem, in other words, is this: according to Newton's inverse-square law for gravitation, the speed at which an object orbits the galactic center (where much of the mass was thought to be concentrated) would decrease inversely with the square root of the orbital radius (Galaxy rotation problem). Thus, stars close to the galactic center would rotate much faster than those near the edges of the galaxy. However, a galaxy such as this would not maintain its spiral shape for longer than a few hundred million years. The spiral "arms" would effectively become diffused, causing the galaxy to be nothing more than a featureless "disc of stars". The fact that there are many observed spiral galaxies suggests that the universe is not old enough for the "collapse" to have occurred, and if the universe cannot be hundreds of millions of years old, it certainly cannot be billions of years old.

Humphreys' point is valid - it is true that results predicted using Newton's simple law of gravitation are not the same as the observed results. This does not mean, though, that the universe is necessarily only a few thousand years old. Instead, the speeds look as represented in Figure 1, in which the predicted inverse-square drop-off is represented by the dotted line labeled A and the observed, fairly constant, value is represented by the solid line labeled B. However, this necessarily begs an explanation.

Whenever observed behaviors do not correspond to predicted results, a new theory is in order. The currently-accepted theory (the one that would require the fewest adjustments to current physical laws) is that there must be some matter, which scientists call dark matter, that keeps the mass, even far away from the central bulge of the galaxy, at a somewhat constant ratio (Galaxy rotation problem). This matter is known as dark matter because, while it influences the universe from a gravitational perspective, it does not emit radiation; thus, scientists are unable to "see" it using conventional telescopes. It is worth noting that scientists have been so far unable to detect dark matter using any direct methods, and have only been able to hypothesize what kind of matter it might be. If this "dark matter hypothesis" turns out to be correct, then there is a great deal of dark matter in the universe - about 23% of all matter in the universe is thought to be dark matter, as opposed to the visible matter, which comprises about 4% of the matter in the universe (Dark matter). The remaining 73% is the so-called "dark energy", which is even less understood than dark matter.

As one can see, attempts to use astronomy to assign a young age to the universe cannot be done. The idea that observed behavior does not match predicted results does not imply that the observations are false and the predicted behavior is true; instead, the model must be checked as well. Thus, in the case of the galaxy problem, one must check whether or not Newton's law of gravitation can be accurately applied in this case. It seems that it cannot. There exists a wealth of astrophysical evidence for an old universe (cosmic microwave background temperature, red-shift velocities, etc.) - one's ascription to a young universe based on a little-understood phenomenon like galaxy rotation requires invalidating well-understood methods of arriving at an old age. In the case in which problems like the galaxy rotation dilemma arise, one must search for a theory to fit the facts; one must not throw out trusted facts in favor of a theory with little or no conventional scientific validity.

Sources:
  1. Humphreys, Russell. 2005. Evidence for a Young World. Acts and Facts, Impact Article #384, Institute for Creation Research. http://www.icr.org/index.php?module=articles&action=view&ID=1842.
  2. Wikipedia. Dark matter. http://en.wikipedia.org/wiki/Dark_matter. Last Updated: 13 November 2005. Accessed: 31 Oct. 2005.
  3. Wikipedia. Galaxy Rotation Problem. http://en.wikipedia.org/wiki/Galaxy_rotation_problem. Last Updated: 11 October 2005. Accessed: 16 Oct. 2005.