On 12/2/2013 10:19 PM, LizR wrote:
On 3 December 2013 11:55, meekerdb <[email protected] <mailto:[email protected]>> wrote:On 12/2/2013 1:14 PM, LizR wrote:On 2 December 2013 20:14, meekerdb <[email protected] <mailto:[email protected]>> wrote: On 12/1/2013 7:35 PM, LizR wrote:On 2 December 2013 16:16, Richard Ruquist <[email protected] <mailto:[email protected]>> wrote: MOND is an alternative explanation that replaces Dark Matter by modifying gravity. Yes (hence the flippant remark about bolt on extras) Dark Matter results when gravity is not modified. (pure Newtonian) Or rather Einsteinian, I don't think Newtonian gravity predicts gravitational lensing?Sure it does, but only half as strong as GR. Ah yes, that's right. I believe that's why the 1919 eclipse data is actually somewhat equivocal, despite catapulting Einstein to fame. (And someone predicted black holes way before Einstein, too, on the basis of Newtonian gravity and the measurement of c - although without realising the full implications ... Mitchell???). Mind you, I think my correction above is still pertinent - that is, it's still truer to say that "dark matter is what results when gravity is not modified (pure /Einsteinian/)".Dark matter would be implied by the same observations even assuming Newtonian gravity. Just the amount would be different. I don't know if Fritz Zwicky even used relativistic calculations of rotation curves of galaxies to infer dark matter - it wouldn't have been necessary since the motions are not that fast. OK. Incidentally I met Zwicky at a party once and he regalled me with the story of how he and a NACA team had actually beaten the Russians into space by launching an artificial satellite *before* Sputnik. When I expressed surprise that I had never heard of this satellite, he explained that it was launched from a B-50 flying at 50kft over the equator using a two stage rocket. When the second stage reached it's apogee, it fired a shaped charge which sent a molten mass of metal into orbit around the Earth. Seriously?!
We were both a little drunk, but he was serious. I asked if the blob of metal had been tracked in orbit? Zwicky said it was too small to track by radar. So then I asked how they knew it entered orbit. He said they knew because telemetry from the second stage rocket showed that it had fired the shaped charge at the right altitude and right direction.
I had not recalled this for many years; the party was in 1963. Consulting the internet (which remembers everything, many of which actually happened) I find that Zwicky wrote a paper about these experiments which differs somewhat from my recollection. http://calteches.library.caltech.edu/1801/1/zwicky.pdf
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