This Day in Science & Discovery — Nov 13: Schaefer Makes the First Artificial Snow and Max Dehn Is Born

Host 1: Welcome to this day in science and discovery on this day November 13th imagine looking up at a cloud and deciding you want it to snow right then and there and you know actually making it happen. Today we're going on a quick deep dive into how a few rebellious minds figured out how to hack both abstract geometry and the physical sky.

Host 2: Yeah so we start in the year 1878 with the birth of German mathematician Max Dehn in Hamburg. And if we fast forward to 1900, the mathematical world was just buzzing.

Host 2: David Hilbert had laid out his 23 major problems to solve for the new century.

Host 1: Right. Those famous Hilbert problems.

Host 2: Exactly. And Den actually solved the third one. He did it by proving a long held suspicion which was that you cannot always cut up a flat faced three dimensional solid and reassemble those exact same pieces into another solid of equal volume.

Host 1: Wait so if they have the exact same volume why can't they be rebuilt I mean it sounds kind of like having two different Lego sets with the exact same amount of plastic but because the blocks have different angles you just can't build the exact same spaceship out of both

Host 2: that is a great way to put it yeah it all comes down to those angles Den created a formula what we now call the Den invariant to measure the lengths of the edges and the angles where the faces meet.

Host 1: Okay, so it's very specific measurement.

Host 2: Right. And unless those specific measurements match up, well, no amount of slicing will let you transform one shape perfectly into the other.

Host 1: I love that. Though, just for accuracy, I should mention the exact date he proved this is a bit disputed. The Saint Andrews archive says 1900, while Wikipedia notes it was part of his habilitation in 1900, but published in 1901.

Host 2: Yeah, the habilitation being essentially a required second PhD for teaching in Germany.

Host 2: But either way, it was the first Hilbert problem solved, and, you know, his math was matched by just an extraordinary life.

Host 1: Oh,

Host 2: yeah so after an arrest in 1938 den made this harrowing two year escape from Nazi Germany I mean he fled through Scandinavia went down to Moscow rode the Trans-Siberian Railway sailed to Japan and finally reached San Francisco in 1941

Host 1: oh wow that is an unbelievable journey

Host 2: absolutely he eventually landed at Black Mountain College in North Carolina he became the only mathematician to ever teach there and he was known for teaching his students outside like while hiking through the mountains

Host 1: that's amazing and he was even buried in the campus woods in 1952 right

Host 2: he was yeah and his legacy is still very active today that den invariant dictates how computer graphics and shape reconstruction work right now

Host 3: Plus, he later introduced the word problem for groups,

Host 4: which proved that certain math questions simply don't have an algorithmic solution.

Host 3: Exactly. That realization sits at the very root of modern computer science.

Host 4: So Den proved you can't always force shapes to do what you want. But you know decades later another pioneer decided to challenge what the atmosphere could do. Basically taking aim at the weather itself.

Host 3: Right. So we jump to 1946 this researcher at General Electric Vincent Schaefer who was actually a self-taught high school dropout he dropped dry ice from a small plane into a cloud over the Berkshire Mountains

Host 4: and the plane was flown by Curtis Talbot right

Host 3: yes Curtis Talbot

Host 4: but this idea actually started in a lab didn't it Schaefer was tinkering around breathed into a chamber cooled by dry ice and instantly saw ice crystals form from the moisture in his breath

Host 3: exactly because dry ice is incredibly cold so when he scaled that up to the sky tossing it into a moist cloud it rapidly dropped the temperature that extreme cold created millions of microscopic ice crystals to act as seeds

Host 4: and then the water vapor clings to those seeds

Host 3: right growing heavy enough to fall as snow

Host 4: now historical accounts differ on the exact payload he used some say three pounds of dry ice over three miles others say six pounds but the result was undeniable within five minutes snow began falling from that cloud

Host 5: though the strangest part is that very first human-made snow never even hit the ground

Host 4: Oh, right. It evaporated or melted in the dry air like 2,000 feet below the cloud bank.

Host 5: Yeah. But even so, that single flight sparked the science of weather modification. If you have ever skied on artificial snow at a resort, you have Schaefer to thank.

Host 4: Not to mention clearing airport fog and modern cloud seeding, though that's handled pretty carefully today, mostly due to ongoing legal battles over who actually owns the water floating in the sky.

Host 5: Definitely a tricky issue.

Host 4: That idea of sky ownership is something to keep in mind, especially when you look at three quick extras also happening on this date. In 1907, Paul Cornu flew a twin rotor helicopter, though Guinness records suggest it was likely just hops rather than true flight.

Host 3: Right. And also in 1893, Edward A. Dewey did discover a vitamin K was born. And then in 1959, Danish physicist Lene Vestergaard Hau was born.

Host 4: She's the one who later led a team that slowed down and eventually stopped a beam of light.

Host 3: Yes, she is. It's fascinating stuff.

Host 4: Which leaves you pondering this. As science figures out how to force snow from the clouds and halt light in its tracks, how will society handle the laws of owning the sky's resources? Thanks for tuning in. See you back here tomorrow.