Have you ever wondered what ice may sound like dropped down a deep icy well? Now, you don’t have to because scientists have just revealed it, and whatever you were expecting, this probably wasn’t it.
A hollow ominous ringing? A final deep thud? Nope, it sounds like a laser gunfight, or a cartoon. Ice apparently falls down a hole to the sound of “pew pew!”
The video of the chunk of ice being dropped down a drill hole to the sound of laser-like pings went viral after geochemist John Higgins shared the clip on Twitter. But there is a good reason for the strange sounds, and an excellent reason why scientists are in the Antarctic drilling holes hundreds of feet deep.
Higgins, an associate professor of geosciences at Princeton, and colleagues were in Antarctica drilling for ice cores that can be thousands, and even millions, of years old. These ancient samples can provide a wealth of information, from ancient climates to atmospheric conditions. In this case, they were looking for gas bubbles trapped in the ice cores, which contain pristine samples of carbon dioxide, methane, and other gases that provide a "snapshot" of conditions back then.
Last year, Higgins was part of a team that discovered the oldest gas bubbles after extracting 2-million-year-old ice cores. Recently they have been back in the Allan Hills, a region at the end of the Transantarctic Mountains famous for its “blue ice” area and the discovery of lunar and Martian meteorites, to take more samples.
Higgins credits Dr Peter Neff, a post-doc researcher at the University of Washington, for the idea of dropping the ice down the borehole. Neff shared a similar video of him and his colleagues doing the same thing in 2018 that had over 10 million views.
As Neff explains in a video he shared online after Higgin's video went viral, they were also in Antarctica taking ice core samples to study ancient air and how the atmosphere “cleans itself”. Studying bubbles trapped in ice cores is like looking at tree rings, we can build records of what the climate was like in the past, he says.
However, “Once you’ve got all these bore holes that you’re done with, you’ve done all the science,” he said. “The logical human thing to do is to throw some ice down a deep hole to see what it sounds like."
So, why does it make that distinctive "pew pew" (just saying the words you can hear it) sound?
Even Laura Dern can't not say it.
The distorted sound as the ice falls is to do with the phenomenon known as the Doppler Effect. This is the change in frequency and wavelength of a wave caused by the change in distance of the source of the wave and the thing observing it. An easy example is the change in pitch when an emergency vehicle with a siren drives past. The soundwaves are compressed as they get closer and stretch out when they get further away, lowering the frequency and pitch.
"When the ice hits the bottom of the borehole, the sound doesn’t only come straight up – the sound waves start to bounce off the sides of the hole. That’s why you hear this plink! with sort of a heartbeat sound afterwards,” Neff said.
So, that's the science, now you can go back to just playing it for the pew pew sound on repeat. As Neff says, it never gets old.