For the first time, researchers have demonstrated that a stable frequency reference can be reliably transmitted more than 300 kilometers over a standard fiber optic telecommunications network and used to synchronize two radio telescopes. Stable frequency references, which are used to calibrate clocks and instruments that make ultraprecise measurements, are usually only accessible at facilities that generate them using expensive atomic clocks. The new technology could allow scientists anywhere to access the frequency standard simply by tapping into the telecommunications network.