Wednesday, July 31, 2013
Shuttlecraft (Star Trek). Galileo Galilei believed in the Copernican model, that Earth travelled around the Sun. Ancient astronomers believed that Earth was centre of the Universe, just as today they insist that the speed of light is constant. After all, the Moon travels around the Earth. Galileo's telescope discovered moons of Jupiter, showing that objects could orbit something other than Earth. So-called scholars refused to look in the telescope, unwilling to upset their world view. Galileo suffered from persecution, trial and house arrest. Today he is honored as one of the great scientists of all time, and by having a Star Trek Shuttlecraft named for him. Galileo also was interested in light. At the time scholars disagreed whether light travelled instantaneously or had a finite speed. Galileo suggested placing lanterns on distant hilltops to time light's passage. Unfortunately, accurate enough clocks did not exist. Galileo's discovery of Jupiter's moons did lead to the first measurement of the speed of light. In 1676 Ole Roemer used an anomaly in observations of the moons to measure the speed of light. Roemer even predicted that one moon would appear late, and observations matched his prediction perfectly. Even Giovanni Cassini, Roemer's boss, didn't believe that light had a finite speed. Roemer's result was not generally accepted for 50 years. Today we have explored the distant hilltop of the Moon. Ancient astronomers insist that the speed of light is fixed, like the Earth. The Lunar Laser Ranging Experiment (LLRE) left behind by Apollo astronauts allows accurate measurements of the Moon's distance. Study of LLRE data shows a huge anomaly in measurements of lunar orbital evolution, indicating that the speed of light is slowing over time. See the paper Calculation of Lunar Orbit Anomaly. Today a Starfleet crewmember still strives to match the example of Galileo.