Re: Wacky new theory about dark matter

Robert J. Bradbury (
Sat, 20 Nov 1999 06:11 EST

Mitch Porter wrote re:

> 1) There are extra dimensions whose radius is only a bit less
> than a millimeter.

> 2) The reason we don't observe atoms leaking out into the
> extra space is because ... [snip of things not worth repeating...]

I believe, I'm paraphrasing Eliezer on another topic, when I say

BLECH! PHOOEY!! GROAN!! KASHMAR!! I've got a theory on how gravitational effects on DNA at the time of chromosomal segregation explains astrological observations but I'm not going to waste good paper by writing it down. The problem here is that data storage bits have gotten too damn cheap...

Please bear in mind a comment offered by a participant at one of the SETI conferences -- if you give the theoretical physicists long enough they can explain *anything*!

Hal offered some comments on dark matter abundances that need clarification.

I believe he expressed the opinion that dark matter abundances are the same in all galaxies. I don't believe this statement may be made with any degree of universality.

Dark matter abundances are "derived" from the rotational rates of the galaxies. Galaxies that show relatively rapid orbital velocities of the outer stars (a failure to decrease in expected orbital velocity with distance from the center of the galaxy, as is the case with the planets relative to the sun) are assumed to have dark matter.

These velocities are determined by the doppler shifts of the stars (or star "aggregates") from the outer to the inner to the outer edge of the galaxy to determine the velocity towards or away from us. Doing this type of experiment requires a fairly accurate spectroscopic equipment and a fair amount of telescope time. The only galaxies this type of measurement can be done accurately for are those that are viewed relatively "edge-on" to us. Due to the equipment and sight restrictions I suspect that quantitative dark matter estimates are available for only a few dozen galaxies. I do not believe there are any estimates on whether the amount of dark matter is increasing or decreasing with the age of the universe (because to accurately determine this we would need the rotational curves of very distant galaxies).

There is also the problem that there is more dark matter in galactic clusters (derived from galactic velocities) than in the galaxies themselves (including the galactic dark matter). There is some recent evidence that some of the dark matter may be neutral hydrogen, but I haven't seen anyone suggest that this explains away the entire problem.

Amara, if I've gotten any of this wrong, please correct it.