The Cosmos reboot season finale (or possibly series finale; not sure if they're trying for a second set of episodes) was last night, but I wasn't able to take part in the live-tweeting of it thanks to a super-restless Pip who didn't drop off until 9:30 EDT. I suppose I could've waited to start the DVR until I would synch up with the West Coast showing, but then, I also need sleep. and I greatly enjoyed being able to fast-forward through the innumerable commercials.
And, really, if you want the story of the Cosmos reboot in a nutshell, there's no better capsule summary than the treatment of dark matter and dark energy. Which they powered through in about ten minutes, with the aid of a hologram Fritz Zwicky and a cartoon Vera Rubin (the criteria for who got a cartoon and who got a hologram remain an utter mystery to me). And without ever uttering the words "Doppler shift."
This struck me as kind of ironic, given this pre-airing tweet from Neil deGrasse Tyson:
#Cosmos was conceived not to tell the you what is true, but to share how we have come to learn what is true.
— Neil deGrasse Tyson (@neiltyson) June 9, 2014
The omission of the Doppler shift completely shifted the dark matter discussion into the "tell you what is true" category, because it's the whole "how." Zwicky came up with the idea of dark matter from measurements of galactic velocities, which by measuring their Doppler shift. Vera Rubin measured the rotational velocities of distant galaxies using the Doppler shift of stars at different positions in the galaxies. Perlmutter, Schmidt, and Riess (and their teams) discovered the accelerating expansion by looking at the Doppler shift of distant galaxies, and comparing it to the distance determined from using supernovae as standard candles.
If you don't talk about motion-induced changes in the frequency of light when you talk about this stuff, you haven't told anybody how we came to learn what's true. The Doppler shift is absolutely essential to this stuff. And it's not even hard to explain, or demonstrate. Instead, we got assertions that these effects were measured by some scientists, over a background of pretty CGI galaxies zooming around, leaving the vague impression that Zwicky measured the velocity of galaxies through some sort of video analysis process. And while Zwicky had a long and interesting career, it wasn't that long.
What's really maddening is that this was followed by a weirdly detailed discussion of the discovery of an ancient supernova via isotopic analysis of manganese nodules from the deep ocean floor. Which was great, don't get me wrong, but was great in exactly the way that the dark matter discussion wasn't-- it really did explain how we know what we know about a billion-year-old supernova. And had they discussed dark matter and dark energy in the same level of detail, I wouldn't be grumping about the show on the Internet.
Given the distribution of these huge lapses, I wonder if the issue wasn't a lack of perspective. That is, the detailed "how we know" material tended to come in areas that are a little outside of astrophysics-- last week's climate science showcase is another great example, with lots of detailed discussion of the evidence for climate change. It feels a bit like what you get from scientists who haven't thought enough about their audience. "Well, of course, everybody knows about the Doppler shift, we don't need to explain that, but this manganese thing is really weird..."
So, as always, it was alternately brilliant and frustrating. The inspirational science-for-everyone stuff was great (I think their description of the process is way too narrow, but that's the subject of the book-in-progress, so I would tend to have Opinions on this). And I'm all in favor of Zwicky and Rubin getting some publicity. But there's the recurring sense that this could've been much better than it was, with only a little re-arrangement of material.
Or fewer commercials, because even fast-forwarding through them, they're really annoying. There were also a couple of places where it felt almost like they had very directly edited out a longer discussion of something to insert a commercial break. I guess we'll find out when the Blu-Ray set arrives (we pre-ordered it a while back...) and we see what sort of Extended Edition features it offers.
But those are a format constraint, a necessary evil endured to reach the huge audience of broadcast tv. Similarly, I found it kind of annoying that there wasn't a sustained narrative to the show-- the episodes were made to stand alone to a large degree, in a way that reduced the overall impact. There were lots of callbacks to previous episodes, but mostly in the form of recurring motifs, not an "as we talked about last week..." kind of thing. The "Cosmic Calendar" thing is a great example-- the damn thing showed up every other episode, it felt like, and every single time we got the description of how it was compressing the entire history of the universe to a single calendar year with each "month" being about a billion years. Which gets kind of tired if you're watching all the episodes as they air, but is a necessary step if you're trying to reach the casual viewer who dozed off during The Simpsons and is waking up to find a science show on instead.
(This is probably the place to plug the Netflix model of making a season as a single coherent whole then dumping the whole thing on the Internet, so anybody who's interested can watch the whole thing in one go.)
A long-narrative approach would've also addressed a lot of my frustrations. Had they been willing and able to use earlier episodes to set up later ones in a coherent way, a lot of things would've been better. The need to make every episode stand alone, though, imposed constraints that made for a bunch of problems. You end up with really perfunctory discussions of complex topics like, well, discussing dark matter and dark energy without talking about the Doppler shift. If they had had a Doppler shift discussion earlier on, though, that they could call back to, it would've been a stronger package. For that matter, a connection between the work of Henrietta Leavitt (mentioned briefly in the token all-woman episode) and the dark energy discussion (drawing the line from Leavitt to Hubble to Perlmutter, Schmidt, and Riess) would've been great, and would've significantly deepened the understanding of science as a connected whole. But, again, that's a constraint you're probably stuck with if you want this on Fox.
Anyway, last night's episode wraps the season-and-probably-series up in a manner that's entirely consistent with the season as a whole. Great visuals, great inspirational stuff, but the science content is only intermittently great, in ways that were pretty frustrating to me.
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I agree about the Doppler shift. Especially as he had, in a previous episode, discussed the line spectra of atoms. It always bothered me, before I knew about line spectra, how they knew how red the lines should be. But he could have, by referencing and showing brief clips from earlier discussions, shown the line spectra, shown them shifted if the source was moving relative to us, and then tied it together to demonstrate how we know the galaxies are moving too fast to be held together by the gravitational pull of the matter we can see.
This would have also illustrated that science is all part of a tapestry, that work in one area often informs and underlies advances in another. But this is me just nitpicking, when I'm grateful for what we did get, in prime time on a major network,
In a way I understood the focus on standard candles; Dr. Tyson did a lot of his student work on 'em.
I agree it'd have been nice to tie in the previous work in the show on Doppler shift and Fraunhoffer lines... but I also agree that the show was likely hampered (in a way the original was not) by the need to jam in ad breaks.
-- Steve
Perlmutter, Schmidt, and Riess (and their teams) discovered the accelerating expansion by looking at the Doppler shift of distant galaxies, and comparing it to the distance determined from using supernovae as standard candles.
Technically, this isn't correct.
We measured redshift, yes. But, it's not a Doppler Shift -- it's a Cosmological Redshift. The former is the result of switching from one inertial frame to another. With distant galaxies, there *is* no inertial frame that's good enough that it applies at both locations. As such, it's not really a Doppler Shift. Redshift is the observed phenomenon; Doppler Shift is one of the possible physical mechanisms that can give it.
It *is* a Doppler Shift for Zwicky's and Rubin's work on clusters and galaxies, because there we are talking about a velocity-included phenomenon. The Cosmological Redshift, though, is a result of the metric of the expanding Universe.
(If you wanted, you could view it as an infinite series of infinitesimal Doppler Shifts -- and you can use a "practical" definition of infinite and infinitesimal as "big enough" and "small enough", for purposes of measurement -- but I think that's more obtuse than just calling it a gravitational redshift that results from the metric changing over time. It's *not* a simple source-frame to observer-frame Doppler shift, however.)
I think you just identified another instance where parts of the show comes across as a class being taught for the first time, while other parts are a honed presentation.
You know, what it really needs is a small audience that drives the script by asking those perfectly timed, insightful questions that you sometimes get in a great class. Less monologue is always good. Galileo found it to be a really effective tool for explaining a new idea.