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...systems and primary energy sources understand the key role of the sun as the main source of renewable energy understand the concepts of energy, power, the difference between them and the essential units used to describe them. The Open University would really appreciate a few minutes of your time to tell us about yourself and your expectations for the course before you...

...system. It was last at perihelion (its closest approach to the sun) in 1995. Each time the comet comes to the inner solar system, it sheds dust. Over time, this debris has built up, and is smeared out along the entire track of the orbit. Once a year, in August, the Earth’s orbit crosses that of comet Swift-Tuttle, and dust from the comet is captured. If you record a...

...system [Images to demonstrate 'Chemical Vapour deposition (CVD)' - see article ] [Diagram showing the Cold Wall System] Hot wall system [Images to demonstrate 'Chemical Vapour deposition (CVD)' - see article ] Manufacture: A “high” temperature process. Cheaper, more suitable for mass-production than PVD (Physical vapour deposition), needing no special attachments,...

...system’s ninth planet upon discovery by Clyde Tombaugh in 1930. He’d been looking for a planet where faulty data suggested a planet-sized body was perturbing the orbit of Neptune. This, he felt, was it – and the world agreed. Pluto’s mass was at first thought to be roughly the same as the Earth’s, but by 1948 estimates had shrunk it to the size of Mars. When...