Slashdot Mirror
Dark Matter Measurements
ksp0704 writes: "According to this article at space.com, scientists have finally measured the approximately 90% of the universe we can't see (the dark matter)." I'm sure it will continue to be a topic of debate for years, but two independent measurements agreeing is a good sign.
Gack. How do they figure an explosion of spacetime is nuclear? There were no nuclei to fuse or split. My cynicism is telling me that the author just though "nuclear" sounded big and bang-y.
Excellent questions. Only problem is that it has no relevance to the "Creation of Normal Matter" the article is talking about.
The "normal matter" they were talking about are baryons (electrons, protons, neutrons etc and their composites). And the "creation" they talk about is "Big Bang Nucleonsynthesis", which is when protons and neutrons and electrons and stuff fuse together to make H, He and Li. The ratio of the production rates of these stuff implies certain "wiggles" in the CMB spectrum, so gives us a gauge (with lots and lots of caveats the scientists don't tell you) to the so-called "baryonic density". (Dark matter, by definition, do not interact with baryons, so it's hard to measure them since all the tools we have are made out of baryons.)
Big Bang Nucleonsynthesis (despite its name) can occur without a Big Bang : we just need the Universe to be Very Hot and Dense at some point.
Your questions about the origins of Big Bang is a much deeper and harder question. While it seems a philosophical argument, it is recently being attacked by some theorists. Most of the time, they just ask the question : do we need a Big Bang that starts from a singularity? The answer, with our current observations, is a BIG NO. But then they have to figure out a better alternative that can give us a very hot and dense Early Universe (so we can have Big Bang Nucleosynthesis, which is a very very very very well observed and constrained theory : i.e. it's fucking correct.)
Mode (3) smart-aleck mode. Press * to return to main menu.
I sure hope you're Ross Tessien, who posted this article to Usenet!
This slashdot comment also looks like this Usenet post.
This slashdot comment also looks like this Usenet post.