In 2015, two giant facilities in the United States caught the shiver of space — a gravitational wave from the collision of black holes. Since then, such signals have been caught regularly, but the detectors themselves are enormous: their arms stretch for kilometers. Now a team of physicists proposes going back to an old idea — using a massive metal bar that rings like a bell when a wave passes through it.
In the new scheme, the bar is placed inside a cavity where light and a few atoms are trapped. The gravitational wave makes the bar vibrate, and its motion transfers to the atoms. The atoms start emitting photons, and this light can be detected. The key innovation: the frequency of the bar's vibration can be tuned so that the atoms emit photons especially readily. This is like tuning a radio to the right station — the signal becomes louder and clearer.
This approach could make gravitational wave detectors smaller and more sensitive. Instead of giant vacuum tunnels — a compact setup the size of a room. This would open the way to a network of inexpensive instruments that could catch signals from neutron star mergers and other cosmic cataclysms.
The first gravitational wave detectors were indeed massive aluminum cylinders weighing tons: they were cooled to near absolute zero and listened to for their ringing.
In the movie Interstellar, the characters use gravitational anomalies to communicate across time — similar to how, in the new scheme, the wave controls the emission of atoms.