3 ms·
The observations in the 1930s you allude to were of the motions of galaxies in galaxy clusters. The rotation-curve measurements for individual galaxies started
by Keysh 5y ago
The observations in the 1930s you allude to were of the motions of galaxies in galaxy clusters. The rotation-curve measurements for individual galaxies started in the 1970s and really took off in the 1980s.
"Tidal effects" are a non-starter, and do nothing to explain galaxy rotation curves. Nor do they explain the excess motions of individual galaxies in galaxy groups and clusters, or the excess pressure of hot, X-ray emitting gas in groups and clusters -- all of which requires either some kind of dark matter, or some kind of alternate theory of gravity, or both.
(I notice that I pointed out the ignorant nonsense of that video when you posted a link to it 7 months ago -- https://news.ycombinator.com/item?id=27085979#27090683 https://news.ycombinator.com/item?id=27085979#27090683)
- Maursault 5y ago> The observations in the 1930s you allude to were of the motions of galaxies in galaxy clusters. The rotation-curve measurements for individual galaxies started in the 1970s and really took off in the 1980s. Nice catch. > "Tidal effects" are a non-starter, and do nothing to explain galaxy rotation curves. Nor do they explain the excess motions of individual galaxies in galaxy groups and clusters, or the excess pressure of hot, X-ray emitting gas in groups and clusters -- all of which requires either some kind of dark matter, or some kind of alternate theory of gravity, or both. What a well formed and well supported argument, and not just a matter of fact statement that you've left entirely unsupported. I'm totally convinced!