Darkling planes

by Henry on October 31, 2003

On the one hand, Bruce Sterling “waxes lyrical”:http://www.wired.com/wired/archive/11.11/view.html?pg=4?tw=wn_tophead_9 about the weirdness of dark matter in WIRED this month. On the other, Jacques Distler “links”:http://golem.ph.utexas.edu/~distler/blog/archives/000242.html to the rather more skeptical (and funnier) “Dark Matter Flowchart”:http://www.astro.umd.edu/~ssm/mond/flowchart.html. We blog; you decide.



Thomas Dent 10.31.03 at 11:06 am

Alas, Mr. Sterling is relaying a massively oversimplified and substantially incorrect version that’s at least 2 levels of hype away from what’s actually been shown by measurement. (Not that the experimentalists weren’t guilty of a degree of hype themselves.)

I’ll just take 2 points: first “Euclid was right all along” because “space is flat”. What the measurements show is that *on the average*, and *on very large scales*, the curvature of space is *less than a certain upper limit*.

This doesn’t rule out either space being curved on large scales, but only slightly so (which was what the “Universe as a football” story was about), and certainly doesn’t rule out curvature on much smaller scales. In fact curvature of space on small scales has been supported by gravitational lensing. That’s to say, observations of distant galaxies are distorted in ways that appear inexplicable without considering curved space.

Second, the assertion that the current accelerating expansion will continue forever. Or, to put it his way, “A gigantic heaving that has worked from the first primal instants and always will”. (Which sounds vaguely obscene.) In fact, the findings of acceleration only apply to the last few billion years (certainly not all the way back to the ‘primal instants’) and, since we don’t understand the nature of the acceleration, there’s no certainty that it’ll always continue.

Andrei Linde (of ‘new inflation’ and ‘eternal inflation’ fame) has published models in which the acceleration stops some time in the next few billion years and we go into a Big Crunch after all.

For all that, the data we have now are literally orders of magnitude more precise than 15 years ago. (Otherwise what would be the point?) But every step away from the data into theories of cosmic evolution introduces an element of uncertainty. As someone (Steven Weinberg?) said, 95 percent of theories are wrong. Maybe 99 percent.


sidereal 10.31.03 at 9:44 pm

Don’t take away my flat, primal heaving

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