Steve Mould, a science YouTuber, educator and author of children’s books on science, in his latest video – which already amassed more than a million views – recorded a phenomenon that, despite being known to scientists, has never been captured on camera before.
The star of the show is a Victorian curiosity, a Water Hammer or “Liquid Hammer Toy” as Mould dubbed it. Essentially, a sealed glass tube with water in a vacuum that produces an unexpected loud clinking sound when shaken. But there’s more to this now forgotten curio, as apart from the unexpected sound, it also produces a small flash of light, albeit invisible to the naked eye.
First, using high-speed cameras, Mould captured the cavitation bubbles that create the clinking sound and flash of light. But as the light of that little flash sits mostly on the ultraviolet spectrum, undetectable to the human eye, he needed a full-spectrum camera.
By default, regular camera sensors can see more than what we are capable of, so they could capture more of the ultraviolet spectrum. But they are made to mimic our vision, and therefore, UV filters are added to the sensors of most cameras. If we remove the UV filter from the sensor, much like how the best cameras for astrophotography are made, we gain a portion of the ultraviolet spectrum back and are able to capture this interesting spectacle.
Watch the full video below for a detailed explanation and a fun science lesson.
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