Posted on 08/02/2002 4:41:48 PM PDT by vannrox
Also, is it thought that the "hot gas" is still being heated? If so, what's the mechanism and source of energy to heat it?
Thanx...
Well, I addressed that to a certain extent in my first post. Here's what they do know: at a small number of specific sample points in the universe, they can measure the extinction function of x-rays, and find that there is a large amount of non-luminous matter in the universe in that direction. That's it. The statistical behavior and amount of extinction agree with what is predicted for gaseous (correct spelling this time) stream of a certain size, density and composition.
The headline of this story is misleading, and is almost certainly not how the scientists couched it in their publication. They probably said something like, "gaseous streams of a certain description are predicted by theory; we have now tested some of these predictions, and they have passed."
It's only your failing if you don't keep asking about what you don't get. Keep firing away and eventually I'll find the right words!
Because matter is electrically neutral on average. This means that the multipole moments of an electric field will be small up to a very large order. Magnetic fields, on the other hand, can have gigantic dipole fields over large distances, but of course these are not ignored by astronomers.
It seems that we do in any case. You can set limits on the density of baryonic matter (i.e. normal matter, made of protons and neutrons) by looking at the relative abundances of the lightest nuclei (hydrogen, deuterium, helium and lithium). If there are too many baryons (protons and neutrons) around, it becomes impossible to construct a model of Big Bang nucleosynthesis that can be reconciled with the abundances we observe.
(The proposed alternate theory revises Newtonian dynamics so that less force is needed to produce very small accelerations.)
I wouldn't call MOND a theory. It's more of an empirical fit.
Democrats.
Hmm, sounds a little liek the "Alderson tramlines" in Pournelle's CoDominum universe, the one that includes the "Mote in God's Eye", and the "The Gripping Hand"
Which originator of the "fit", who is also the author of the SciAmer. article, admits. Upon reading the article, I wondered about some sort of quantum gravity effect at very low levels of graviation. But that's just idle speculation. I certainly don't have the mathematical background to even attempt to investigate the idea.
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