The Natural History Museum of Utah and the Utah Film Center are putting on their free Science Movie Night next week at the downtown Salt Lake City Public Library. The series pairs a movie with an expert to discuss the real-world science amid the science fiction — and Tuesday, it's Garrett's snowflake expertise with "Doctor Who: A Christmas Carol."
In the British Christmas special, The Doctor (Matt Smith) is trying to save a spaceship full of people from crashing as it's torn apart in a tumultuous cloud layer on Christmas Eve. Unfortunately, the only person who can operate the machine that will stabilize the clouds is the Scrooge-ish Kazran Sardick (Michael Gambon, better known as the second Dumbledore) who delights in referring to a deadly crash as "a kind of landing."
So how does Grumpy Dumbledore's machine stabilize clouds, and is it real science? As The Doctor explains: "[Sounds] resonate in the ice crystals causing a delta-wave pattern … Of course, that's how the machine controls the cloud belt. The clouds are ice crystals. If you could vibrate the crystals at exactly the right frequency, you could align them."
Actually, no, that doesn't work, according to Garrett, a self-professed "Doctor Who" fan; at least not as far as scientists understand sound waves and clouds.
"It's 'Doctor Who' … they take their usual cinematic liberties with the topic," he said. "I don't think that flying sharks [like the one in the movie] are really intended to be scientifically real … but they do talk about ice clouds in the show. The atmosphere does contain ice clouds."
And manipulating clouds is definitely real, Garrett explained. For instance, pilots spray silver iodide in clouds to turn the water particles into ice and snow, which fall to Earth and turn into rain on their way down. It's called "cloud seeding" and is used for agriculture. Garrett plans to demonstrate that effect on stage at Science Movie Night, with his own "sonic screwdriver" (a decorated syringe) filled with silver iodide.
He's also a leading researcher on a project that photographs snowflakes as they fall, which produces both dazzling pictures and important results. For a long time, people have based their weather forecast models on the snowfall in the Cascade Mountains. But what Garrett and his colleagues have found is that the snow that falls on the Wasatch Mountains is very different. If you want to find out how so, and what that means for your impending winter forecasts, feel free to ask him after the movie.
The Christmas special starts at 7 p.m. Tuesday in the downtown Salt Lake City Library auditorium.
— Michael McFall