Last year, scientists drove up Mauna Loa volcano on Hawai'i, aimed a laser at a reflector positioned on Haleakala peak on Maui, and beamed rapid pulses of laser light through 150 kilometers of turbulent air. While the pulses were exceedingly faint, they demonstrated a capability long sought by physicists: transmitting extremely precise time signals through the air between far-flung locations at powers that are compatible with future space-based missions.
