Last night's episode of Cosmos: A Spacetime Odyssey looked at the tiniest elements of our universe, exploring plant and animal cells and the role they play in our lives. Host Neil deGrasse Tyson took us inside plants, water, and our brains and reminded us, once again, that the laws of nature both constrict and expand our understanding of life. At the end of the episode we were again confronted with the beginning of our cosmic calendar and the impenetrable Wall of Forever. But before that, he gave us quite a bit to consider. 

The universe fits inside a drop of water 

Danielle: I don’t even know where to start with last night’s episode. Tyson covered particle physics, the periodic table, chlorophyl and photosynthesis, olfactory memory, and more. He somehow managed to pull together topics across the scientific field with grace, and I think that’s thanks to some of the legwork done earlier in the series. For instance, bringing back the tardigrade was a good way to remind us that a size does not make an animal (or atom, or element) any less formidable -- a weirdly comforting thing for humans talking about the universe.

Abby: Right. Here we had the storyline of the boy, picking fragrant flowers in a dew-covered field, approaching a girl he likes. But instead of going inside the familiar narrative of the emotions or human dynamics at play in such a scene, Tyson took us inside everything else: why does the smell of the flowers evoke a certain memory? How is that smell transmitted to our brain? 

'Molecular industrial process' via Hulu.

Danielle: I was totally fascinated by the idea of plant cells as containing a "molecular industrial complex," and the notion that we could possibly use photosynthesis as a model for green energy. Tyson used a rather wonky analogy to flesh out this idea, saying, "We're on an industrial espionage mission. If we can penetrate the trade secrets in the manufacturing process in that chloroplast, let's just say our whole future hangs in the balance." The representation of photosynthesis as an efficient manufacturing process lends credence to green energy as a viable option. I like this as a way to both make a case for sustainability that would appeal to financial skeptics, rather than science skeptics, while also delivering a rhetorical blow to climate change deniers by refusing to discuss global warming as anything other than a given. 

Abby: Yeah, that was a good analogy. It also does something well that Tyson et al. have done again and again this series: tease the idea of what could be our future as science continues its work. The "spacetime" part of the show's structure (it's in the title) is clearly trying to make a statement about the speed with which humans can advance scientific discoveries, at least when powerful people and institutions with other ideas about how the world works are prevented from interfering or outright destroying that progress. The whole promise of a new industrial revolution, if only we could harness what plants can do, seems to fit this narrative. 

Danielle: I think the theme that tied together the range of topics presented last night --- and one each episode has been implicitly grappling with -- is the power of the unseen. Tyson says "there can be no stronger test of an idea than its predictive power," in explaining how Darwin correctly hypothesized the existence of the Morgan's Sphinx. In a field where discoveries are pegged to events billions of years old and hypotheses are unlikely to be confirmed by the scientists who formulated them, this must be comforting. 

Abby: And we saw that in this week's history lesson, too. The dramatized version of Democritus explaining his atomic hypothesis to a crowd of wine-guzzling admirers presents an argument for the poetry of discovery. Democritus rejects the response of "that's it?" to the idea that we're all just tiny molecules invisible to the naked eye, instead providing a view of atoms as the source of the variety of all life on Earth. It's supposed to be a wonderful thought. 

Danielle: I wonder when Cosmos will start discussing the possibility of alien life. This episode seems to be a pretty good precursor to that, with its focus on liquid water (which scientists consider necessary for alien life) and carbon, the atomic building block of life. 

Abby: They've teased the idea before, but yes. The search for extraterrestrial life was a major part of Tyson's predecessor Sagan's work, so I think this is probably something those with some nostalgia for the original Cosmos are hoping for. 

Inside the Super-Kamiokande detector, via Hulu.

Danielle: Yes. I have a feeling the payoff will be a good one, though. I want to mention, again, the especially moving scene in which the boy pressed the girl's cheek, and Tyson explains that they're not really touching. It’s an emotional iteration of a rather jarring scientific fact -- the sensation of touch is not a result of what we perceive as the act of touching -- that is in keeping with last week’s creative episode and makes us viscerally question our surroundings, which is what the show is all about. 

On another note, I'm actually a bit surprised that this episode didn't discuss the Higgs Boson, the particle theorized in the 1960s and confirmed last year, which is key to our understanding of the big bang. 

Abby: But we got neutrinos! So many neutrinos. 

Danielle: Yes! That Japanese neutrino detector is frankly gorgeous, much more magical-looking than I would have imagined. Not entirely sure the scientific value of sticking a raft in there, but I'm not complaining.  

Abby: I also like the part of this episode when Tyson doesn't exactly discourage viewers at home from putting a cannonball on a rope and swinging it right in front of your face. Bet you won't see THAT DIY science idea in a classroom textbook. 

FOX

Danielle: Oh that was so great. Maybe I missed something, but for the most part last night's episode didn't confront religion as much as the others (aside from the discussion of ancient Egyptian temples, but that seemed like more of a historical thing). Of course, that doesn't mean that people have taken a break from campaigning against the show. Just last week, devoted Oklahomans protested against the show, threatening to secede (from something) and warning of a natural disaster if Cosmos isn't cancelled. 

Abby: If only they'd watched this week's episode, those protesters would know that we've had a better explanation for natural disasters ever since the ancient Greek philosopher Thales posited that bad weather wasn't a sign of God's wrath. Oh well. 

But what did the Internet think?

Based on a number of tweets, it looks like I wasn't the only one excited by the return of the tardigrade. 

And some people picked up on the anti-creationist implications of the discussion of atoms: 

The episode discussed the sun and supernovas, which meant that NASA had a chance to show off a little: 

And finally, some raised the concerning point that female scientists are absent from Tyson's list of heroes, although I would suspect this has more to do than the more-concerning lack of women in the field than any bias on Tyson's part: 

What we learned

Danielle: I didn't know that the orchid was the oldest flower, and I certainly didn't know that Darwin predicted the existence of an animal, which is pretty awesome. I didn't know that neutrino detectors look so sleek, and I didn't know anything about Thales or Democritus. I didn't know that scent triggering memory was an evolutionary survival mechanism. 

Abby: Yes. If I did know about the amygdala and hippocampus's  proximity to the olfactory nerve, then I'd forgotten all about it. I think most of us know instinctively that scent can evoke powerful memories and emotional reactions. I liked learning about how that works. 

Check out our discussions of previous Cosmos episodes below: 

Episode one: What Does Neil deGrasse Tyson's Cosmos Say About Religion?

Episode two: Neil deGrasse Tyson Addresses Creationists' Evolution Fears in Cosmos

Episode three: Neil deGrasse Tyson Makes Us Feel Inadequate on This Week’s Cosmos

Episode four: Neil deGrasse Tyson Says Time Travel Is All Around Us on This Week’s Cosmos

Episode five: Neil deGrasse Tyson Shows Us How to See Sounds on This Week's Cosmos