Big Vinnie barrels into the office, again. “Hey, Sy, word is you been short-changing Fritz Zwicky. What’s the story?”
“Hey, I never even met the guy. He died in 1974. How could I do him a bad deal?”
“Not giving him full credit. I read an article about him. He talked about ‘dark matter’ almost fifty years before Vera Rubin.”
“You’ve got a point there. Like Vera Rubin he had a political problem, but his was quite different than hers.”
“Political? I thought all you had to do was be right.”
“No, you have to be right and you have to have people willing to spend time validating or refuting your claims. Rubin wasn’t a self-advertiser, so it took a while for people to realize why her results were important. They did look at them, though, and they did give her credit. Zwicky’s was a different story.”
“Wasn’t he right?”
“Sometimes right, often wrong. Thing was, he generated too many ideas for people to cope with. Worse, he was one of those wide-ranging intellects who adds one plus one to make two. Trouble was, Zwicky got his ones from different specialties that don’t normally interact. When people didn’t immediately run with one of his claims he took it personally and lashed out, publicly called ’em fools or worse. Never a good tactic.”
“Gimme a f’rinstance.”
“OK. Early 1930’s, Zwicky’s out in the still-raw wilds of California, practically nothing out there but movie studios and oil wells, using a manual blink-comparator like the one Clyde Tombaugh used about the same time to find Pluto. He’s scanning images taken with Palomar’s new wide-angle telescope to search out novae, stars that suddenly get brighter. He’s finding dozens of them but a few somehow get orders of magnitude brighter than the rest. He and his buddy Walter Baade call the special ones ‘supernovae.'”
“Ain’t that novas?”
“Novae — we’re being proper astronomers here and it’s a Latin word. Anyway, Zwiky’s trying to figure out where a supernova’s enormous luminosity comes from. He got his start in solid-state physics and he still keeps up on both Physics and Astronomy. Just a year earlier, James Cavendish over in atomic physics had announced the discovery of the neutron. Zwicky sees that neutrons are the solution to his problem — gravity can pack together no-charge neutrons to a much higher density than it can pack positive-charge protons. He proposes that a supernova happens when a big-enough star uses up its fuel and collapses to the smallest possible object, a neutron star. Furthermore, he says that the collapse releases so much gravitational energy that supernovae give off cosmic rays, the super-high-energy photons that were one of the Big Questions of the day.”
“Sounds reasonable, I suppose.”
“Well, yeah, now. But back then most astronomers had never heard of neutrons. To solve at a stroke both cosmic rays and supernovae, using this weird new thing called a neutron, and with the proposal coming from somewhere other than Europe or Ivy League academia — well, it was all too outlandish to take seriously. No-one did, for decades.”
“He didn’t like that, huh?”
“No, he did not. And he railed about it, not only in private conversations but in papers and in the preface to one of the two galaxy catalogs he published. Same thing with galaxy clusters.”
“Wait, you wrote that Rubin found clusters.”
“I did and she did. Actually, I wrote that she confirmed clustering. We knew for 150 years that galaxies bunch together in our 2-D sky, but it took Zwicky’s measurements to group the Coma Cluster galaxies in 3-D. Problem was, they were moving too fast. If star gravity were the only thing holding them together they should have scattered ages ago.”
“Dark matter, huh?”
“Yup, Zwicky claimed invisible extra mass bound the cluster together. More Zwicky outlandishness and once again his work was ignored for years.”
“Even though he was right.”
“Mm-hm. But he could be wrong, too. He didn’t like Hubble’s expanding Universe idea so he came up with a ‘tired light’ theory to explain the red-shifts. He touted that idea heavily but there was too much evidence against it.”
“One of those angry ‘lone wolf’ scientists.”
“And bitter.”
~~ Rich Olcott
“Not much. We can’t see it, and they say there is much more of it than the matter we can see. If we can’t see it, how did she find it? That’s a thing I don’t understand, what I came to your office to ask.”
“So you’re telling me, Cathleen, that you can tell how hot a star is by 
Cathleen turns to her laptop and starts tapping keys. “Let’s do an example. Suppose we’re looking at a star’s broadband spectrogram. The blackbody curve peaks at 720 picometers. There’s an absorption doublet with just the right relative intensity profile in the near infra-red at 1,060,190 and 1,061,265 picometers. They’re 1,075 picometers apart. In the lab, the sodium doublet’s split by 597 picometers. If the star’s absorption peaks are indeed the sodium doublet then the spectrum has been stretched by a factor of 1075/597=1.80. Working backward, in the star’s frame its blackbody peak must be at 720/1.80=400 picometers, which corresponds to a temperature of about 6,500 K.”
“You’re right, Sy. It’s not a particularly pretty picture, but it shows that nice strong sodium doublet in the yellow and the broad iron and hydrogen lines down in the green and blue. I’ll admit it, Vinnie, this is a faked image I made to show my students what the solar atmosphere would look like if you could turn off the photosphere’s continuous blast of light. The point is that the atoms emit exactly the same sets of colors that they absorb.”
“Whoa, Sy. Do you read the final chapter of a mystery story before you begin the book?”
“It is, Sy, and that’s one of the reasons why Hubble’s original number was so far off. He only looked at about 50 close-by galaxies, some of which are moving toward us and some away. You only get a view of the general movement when you look at large numbers of galaxies at long distances. It’s like looking through a window at a snowfall. If you concentrate on individual flakes you often see one flying upward, even though the fall as a whole is downward. Andromeda’s 250,000 mph march towards us is against the general expansion.”
Hard Science Ain't Hard 
