As followers of this blog know, data from the Lunar Laser Ranging Experiment, also left on the Moon by astronauts, may reveal a changing speed of light. As Galileo suggested, light can be timed using lanterns on distant hilltops. Galileo lacked an accurate clock, but today we have access to laser lanterns and the distant hilltop of the Moon. 40 years of laser ranging report the Moon receding anomalously high. If the speed of light were slowing, time for light to return from the Moon would increase each year, making the Moon appear to recede faster. Missions to the Moon are a priceless asset for cosmology.