Science Behind the Photo #34

Moon Bouncing

Taken in 2008, this pair of telecommunications masts in downtown Atlanta, USA carry a mix of phone, TV and radio relay dishes. Telecommunication towers have been around since the early 1900s. It was Nikola Tesla, in the 1890s, who first proposed that radio waves might be used for the communication of information. The first radio broadcast of a human voice was probably that made by Reginald Fessenden on Christmas Eve in 1906 from Massachusetts, USA. The rest, as they say, is history. A study published this year in Science estimated the world’s effective capacity to exchange information through two-way telecommunications networks grew to 65 exabytes in 2007.

Radio waves have been streaming into deep space since their invention, but not all of them get away. There’s a transmission technique called ‘moon bounce’, which reflects radio waves off the Moon’s surface back to Earth, making a telecommunications relay of the moon itself. As part of the celebrations in 2009 leading up to the 40th anniversary of the Apollo 11 moon landing, the world celebrated Moon Bounce Day. One of the highlights was a moon-bounce-transmitted interview with Apollo 8 astronaut (and Apollo 11 back-up) Bill Anders. Incidentally, Anders is also one of the tiny handful of living people to have experienced complete radio black-out, when orbiting the Moon’s far side.

More > here’s a beautiful close-up of the very same Moon and here’s a post about wireless communication and eccentricity.

Image: Douglas Heaven

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