Perigean spring tide Perigean spring tide A proxigean spring tide (also known as a perigean spring tide) is a tide that occurs three or four times per year when the Moon's perigee (its closest point to Earth during its 29.5-day elliptical orbit) coincides with a spring tide (when the Earth, Sun and Moon are nearly aligned every two weeks). This tide usually adds only a couple of inches to normal spring tides. The Moon's orbit around Earth is elliptical, which causes the Moon to be closer to Earth and farther away at different times. The Moon and the Sun are aligned every two
Earth–Moon–Earth communication Earth–Moon–Earth communication Earth–Moon–Earth communication (EME), also known as moon bounce, is a radio communications technique that relies on the propagation of radio waves from an Earth-based transmitter directed via reflection from the surface of the Moon back to an Earth-based receiver. The use of the Moon as a passive communications satellite was proposed by W.J. Bray of the British General Post Office in 1940. It was calculated that with the available microwave transmission powers and low noise receivers, it would be possible to beam microwave signals up from Earth and reflect off the Moon. It was thought that at least