Scientists Film Sonic Boom Made of Lasers With High-Speed Camera
Scientists have managed to film a "sonic boom" made of light by building one of the fastest cameras in the world. The camera could be used to film other high-speed events like neurons firing or neutrino collisions. Their research is published in a paper in the journal Science Advances.
A typical sonic boom is caused when an airplane breaks the sound barrier, meaning that it's traveling faster than the speed of sound in air. As the aircraft increases its speed, pressure waves build up on it and eventually coalesce into a single shockwave. When a plane outruns that shockwave, it causes a sudden change in pressure, which in turn creates a sonic boom.
A similar thing can happen with light. When light passes from air into a denser material like glass or water, it slows down. This transition can create shockwaves of light similar to the shockwaves created by a plane breaking the sound barrier.
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To create a light "sonic boom," the researchers shined a laser into a panel of silicone glass. Light in silicone glass travels about 30 percent slower than light in air, so when the laser light passed from the air into the glass, it produced a sort of "sonic boom."
To film the light in real time, the researchers needed to build some fancy tech. Their custom-built camera can capture billions of frames per second, making it one of the fastest in the world, and the fastest single-exposure camera.
Most extremely high-speed cameras work by filming a repetitive event, like a laser pulse, many times in a row and combining several partial recordings into a single complete one. This camera, however, can capture such an event even when it happens just once. As IEEE explains:
Just as a CT scanner uses slices of an X-ray to build up a 3D picture of an organ, [the system] allowed a computer to divide the single snapshot into slices and rebuild them into a three-dimensional data cube that separated the slices in time and space, giving shape to what would otherwise have been just a smudge of light.
The ability of this camera to shoot as such high speeds and capture non-repeating events could give us the chance to film other sorts of lightning-fast events as well, like neurons firing in the brain. Only time will tell if they look half as cool as laser sonic booms.
Source: LiveScience and IEEE Spectrum
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