Seth Horowitz’s first chapter of The Universal Sense is practically tailor-written to my interests. I’ve always been fascinated by the collision of space bodies, and the high-velocity impact experiments designed to simulate the conditions of these impacts (at a very small scale) was a great segue to the pivotal role sound has played in our evolution. It’s easy to think of sound as an invisible force with an almost physically solid presence. When we hear sounds, it’s so often a result of an observably physical interaction. A hammer strikes a nail and an appropriately sharp and loud sound accompanies. Tires squeal, horns blare, and steel crumples to announce an automobile accident. Soft clicking and clacking, sporadically rapid, telegraphs the process of composing this blog post.

Perhaps it is because our most intellectually and emotionally meaningful auditory experiences – chiefly music and speech –run contrary to this falsely-percussive trend, we yet maintain a peripheral awareness of sound as something more intangible. As Horowitz explains beautifully, we are evolutionarily hardwired to pay immediate and fearful attention to loud, sudden, booming sounds. We’re unnerved by thunder, low-flying jets, or any other eruptive or explosive sound because our primitive, skittish, self-preserving brain kicks in with the message “I have no idea what that was; time to go!”

This is beautifully demonstrated in the well-documented reactions to February 2013 Chelyabinsk meteor event. Scores hundreds of videos on YouTube depict the moment the sonic boom strikes thousands of Russians, minutes after the meteor rips through the upper atmosphere. As the boom hits, people run away from breaking glass, scream in shock, or swerve erratically when driving. As is the case with the man recording the video below (about 30 seconds in), the primate brain kicks in each time, always with the impetus to duck or flee. It may be physically intangible, but sound’s presence in the human mind is solid as a rock … ripping its way through Earth’s atmosphere at supersonic speeds.