> the hemispheres are carefully lined up by hand and then they pull vacuum. I'm guessing it was not very close to vacuum? The article mentions air explicitly:

> the hemispheres are carefully lined up by hand and then they pull vacuum. I'm guessing it was not very close to vacuum? The article mentions air explicitly: > As the instrument's glass collapsed under the weight of five miles of water, it released a pocket of air that oscillated under pressure before splintering into a veil of tiny bubbles.