By Jeremy Hsu
Within one second of the big bang, the first newborn black holes may have announced their formation with gravitational waves that stretched and squeezed the fabric of existence as they rippled outward into the expanding universe. Now researchers at Northwestern University have begun planning a tabletop-size sensor that could detect these primordial howls for the first time.
The gigantic $1-billion Laser Interferometer Gravitational-Wave Observatory (LIGO) first measured the spacetime ripples known as gravitational waves in 2016; these phenomena came from the collision and merging of distant supermassive black holes. Since then, massive detectors have also recorded gravitational waves from merging neutron stars. Northwestern’s proposed mini detector, which received an influx of funding in July, could measure higher-frequency waves from objects that have never been measured before—such as black holes in the earliest universe.
Current gravitational-wave detectors such as U.S.-based LIGO and Europe’s Virgo use a sprawling system of mirrors and laser “arms” that stretch for kilometers to measure tiny changes in distance caused by passing gravitational waves. Northwestern’s Levitated Sensor Detector would use lasers to suspend a glass bead inside a vacuum chamber, creating an extremely force-sensitive sensor with arms just a meter long. It would listen for echoes from the formation of primordial black holes and the activity of theoretical particles called axions, both of which are candidates for mysterious dark matter—hidden materials that may constitute much of the universe’s mass and are invisible except for their gravitational presence.
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