Re: Galactic pancake mystery solved
Tim Killian wrote:
It was data from Tycho's _observations_ that lead a frustrated Kepler
to try an elliptical motion model!
Of course. I said this already.
But Tycho didn't see ellipses in the sky. He saw planet positions that
didn't agree with the current theory. And Kepler wasn't led to ellipses
by experiment. He assumed them, then simulated them numerically and
demonstrated that they fit the facts.
My pique with the satellite galaxy model is the authors use of a model
with multiple levels of assumptions including a cold dark matter theory
that has no experimental evidence to support it.
I think you're putting the cart before the horse.
There is abundant evidence from independent sources that the motions of
galaxies and the large-scale structure of the universe are inconsistent
with the mass we can see.
That's the Tycho, discrepant facts stage. Now we're at the Kepler stage,
where we brainstorm ideas and simulate them numerically to see whether
we can account for the facts.
We've known about the problem for over 70 years, and all the simple
models have already been tried. So now we're discarding our cherished
circles and trying some ellipses.
There was no experimental evidence to support Kepler's second law. That
had to wait for Newton and the formulation of a physical theory that was
testable at human scales. And we aren't going to find dark matter in
accelerators--or reject its existence--until we understand the problem
well enough to formulate a theory that makes testable predictions.
- Ernie http://home.comcast.net/~erniew
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