[XCSSA] Legos and Dark Matter

[xcssa@xcssa.org]

Tom,

Thanks for the great Lego Mindstorms adventure!  I made 3 different 
robots during the lab, the final one being a robot which changes 
direction after hitting a room boundary.

Worst problem was the somewhat cumbersome GUI of the development 
environment, having a number of faults like a lack of undo, clunky 
methods for deleting things (and no way I could figure how to move 
things around), and my computer was missing the built-in documentation 
files, so it was hard to figure out what I was supposed to do except by 
trial and error, then deleting everything and starting over.  

But it was still good enough to get programs working in a few minutes.  Fun!

***** Dark Matter  *****

Thanks also for mentioning the latest discovery about dark matter.  I'm 
pretty sure I didn't hear about it last month at the Dark Matter and 
Dark Energy seminar I went to.  I see it was posted to NASA more than a 
week after that seminar, so it's the latest stuff:

http://www.nasa.gov/home/hqnews/2006/aug/HQ_06297_CHANDRA_Dark_Matter.html

NASA scientists say they observed a situation which they say can only be 
explained by Dark Matter, not alternative gravity theories.

I wouldn't be entirely surprised, however, if the people with 
alternative gravity theories (to eliminate the "need" for dark matter by 
saying gravity does not decrease the same way at large distances 
instead) have some different interpretation.  Maybe I'll find out at the 
cosmology colloquium I'm going to next month.

But it was really good to find this out before going!  This is the kind 
of late breaking news one always gets at XCSSA!

Also, checking the background on dark matter, the key finding that led 
to the dark matter theory was the way many galaxies rotate.   Stars near 
the outside of these galaxies apparently rotate FASTER than would be 
predicted assuming that the majority of the mass is associated with hot 
gas (stars), which tend to be clumped near the center.  (Based on 
visible mass, we would have expected the outer portion to rotate much 
slower than the inner, but instead the rotation is more uniform.)  This 
was first measured accurately by Vera Rubin who studied galaxies which 
we view on edge so the red shift between the inner and outer stars can 
be compared.

(In that regard, however, the non-Big Bang theorists say these aren't 
huge galaxies at all, but smaller clusters of gasses, so it's not 
surprising center and out parts rotate at similar speeds.  There are 
still a few of these guys around, such as the important but elderly 
astronomer Halton Arp, who have alternative interpretations of nearly 
everything you've heard, including the red shift itself and the 
cosmological background radiation.)

One thing that hasn't happened yet is showing exactly what the alleged 
Dark Matter really is.  Nor Dark Energy.  So it turns out we don't 
really know yet what apparently 96% of the universe is made of.  We also 
have two very well established (and useful) theories in Physics, General 
Relativity and Quantum Mechanics, and at certain key points they give 
different predictions.  For example, Black Holes are not consistent with 
the standard model of Quantum Physics.  The two theories just don't fit 
together in a lot of ways, and lots of scientists now are trying to find 
a new theory to replace both, just as Einstein failed to do in the last 
decades of his life.

So much for science being near the end, like one recent book says. 
 Actually, it looks like we're due for another scientific revolution.

Charles