Diego Blas

In 2034, a rocket leaves a spaceport with an unusual payload: two spheres the size of a large globe, each weighing nearly a ton. No engines, no electronics. Just a mirrored surface of hundreds of corner-cube reflectors — tiny prisms that return light exactly to where it came from. This is the future space tuning fork.

A thrown stone sends ripples across water. A gravitational wave is the same kind of ripple, but in spacetime. It is produced, for example, by the merger of two black holes. In classical physics, this ripple is eternal: once created, it travels through the Universe without fading.

In the shaft leading to the Large Hadron Collider, an unusual tenant may soon move in: a hundred-meter vertical tube where clouds of strontium atoms will be dropped. Each cloud is cooled to near absolute zero, so the atoms move slowly and in sync, like dancers in slow motion.