Things get small — really small — in this week’s episode of "Cosmos," which tackles the unseen universe at the atomic scale, from the teeming ecosystem inside a single dewdrop and the intricate machinery inside a plant’s cells, to the subatomic particles at the heart of a giant exploding star.
Carl Sagan famously observed that we are made of star stuff, but that star stuff in turn is made of atoms — the fundamental building blocks of nature — and there are more atoms in the human eye than there are stars in the known universe, according to our host, the Collection of Atoms Known as Neil de Grasse Tyson. (He should come up with own unique sigil, like Prince.)
Once again, we have a slightly haphazard organization of segments, with a generous peppering of random True Facts for garnish. Since the episode is ultimately all about atoms, let’s start there rather than the whimsical journey into a dewdrop to marvel at the pitched battle between a paramecium and its mortal enemy, the suctorian, and to coo over totes adorbz images of tiny pink tardigrades (a.k.a. water bears).
We’ll also skip the bit about Charles Darwin studying an orchid native to Madagascar and predicting that because the pollen was buried so deep inside the stamen, there must be a flying insect with a super-long tongue capable of reaching said pollen. He was right: 50 years later a new species of hawkmoth was discovered with a foot-long tongue. Don’t get me wrong, it’s a delightful story; I just have no idea what it’s doing in this episode.
Anyway, the notion of atoms dates back to an ancient Greek philosopher named Democritus, who first proposed that it just wasn’t possible to keep dividing matter into smaller and smaller bits; at some point, you would reach the smallest possible piece, which he dubbed “atomos” (“not to be cut”). His contemporaries, including Aristotle, didn’t take Democritus seriously, and why should they? They didn’t have the tools to probe such a small scale. But eventually modern physics proved him right.
Just how small are we talking? The Ship of the Imagination takes us into the slightly steampunk molecular industrial complex of a plant cell, courtesy of a nifty animation. This is where plants achieve the miracle of photosynthesis, converting sunlight into energy, taking carbon dioxide and turning it into oxygen. (Humans do the opposite.)
This is an example of a complex biological molecule, made possible thanks to carbon. Something inert, like quartz (a crystal), has a precise, repetitive atomic structure because there are only a limited number of ways those atoms can be arranged. But a carbon atom is promiscuous little beast, able to bond with pretty much everything else. And that extraordinary flexibility is the key to life.
Atoms are even smaller than molecules. There’s a charming scene with a little boy presenting a little girl with a bunch of lilacs and gently poking her cheek with his index finger as her glowering father looks on. But as Tyson points out, at the atomic scale, the boy didn’t get near to touching her, because atoms are mostly empty space. Our sense of objects as being solid comes from electromagnetic repulsion. You think your derriere is really touching the seat of that chair you’re lounging in? Think again. The only time atomic nuclei really touch is when they fuse in the giant nuclear furnace of star like our sun.
That nuclear fusion is why the sun shines, converting hydrogen into helium — although larger, even hotter stars than our sun can fuse helium. The largest stars live fast and die young, exploding into supernovae, scattering its matter throughout the universe, including billions of ghostly subatomic particles called neutrinos.
Cut to the Collection of Atoms Known as Neil de Grasse Tyson chilling in an inflatable lifeboat, deep under the Earth in Japan’s Super Kamiokande neutrino detection chamber. The Higgs Boson has gotten all the love the past couple of years, but neutrinos have had moments in the spotlight too; John Updike penned a famous (and accurate) poem, “Cosmic Gall,” in their honor back in the 1950s. They have little mass and interact primarily via the weak nuclear force, which makes them difficult to detect.
Physicist Wolfgang Pauli first proposed the existence of the neutrino as a means of explaining why conservation of energy appears to be violated when the nuclei of certain radioactive atoms spontaneously eject an electron, thereby transforming into a different element — a kind of nuclear alchemy.
This is a perfect excuse to resurrect a classic physics demonstration with a tethered bowling ball; our host lifts it slightly and releases it, so it sweeps out into a wide arc before hurtling back toward Tyson. But does he flinch? He does not. Neil de Grasse Tyson knows no fear — because he knows his physics. Energy is conserved, so as long as he doesn’t give the ball an extra push, the swing will stop just short of hitting his dapper face.
The point is that the energy accounting books have to balance. So where does the missing energy from the radioactive nucleus go? Pauli surmised it was carried off by a neutrino, a prediction that was verified in the 1950s when neutrinos were detected in the radiation streaming from a nuclear reactor.
Trust me, neutrinos are fascinating little particles, and they’ve been surprising scientists for decades. But their real significance might just be the very thing that makes them so difficult to detect: those ultra-weak interactions.
See, we can see pretty far back into the early history of our universe with the instruments we have now, but eventually we hit what Tyson dubs the Wall of Forever, better known as the Cosmic Microwave Background Radiation, the afterglow of the Big Bang. It’s the baby picture of the cosmos when it was just about 318,000 years old. Scientists have yet to pierce that glowing veil shrouding the 317,000 years that came before.
Here’s the thing: In the beginning, there were also neutrinos, and those particles have traveled across that vast expanse of space and time with few interaction with other particles. So they could still contain useful information about those very first moments, when the cosmos was still the size of an (incredibly dense) blue marble.
So neutrinos — among the smallest of the very small things in our universe — could end up being the key to seeing beyond that Wall of Forever. Let’s see a dewdrop do that.