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...courses and qualifications A crystal set is the most basic type of radio receiver. It is capable of receiving AM (amplitude modulated) transmissions, which are generally found on the long, medium and short wave bands. The magic of the crystal set is that no power source is required; a tiny fraction of the transmitted signal provides sufficient power for the signal to be...

...courses and qualifications [vial of gold] Why is gold so expensive? Gold is an unusual metal in that it predominantly exists in the Earth’s crust as the element (so-called ‘native’ gold); that is, it’s not chemically combined with other elements. Silver and copper are the only other metals naturally found in their elemental form. Gold is a relatively rare element,...

...course of 40 hours. After analysing their data, they found that the planet transit began 77.8 minutes earlier than predicted. This is interpreted as a so-called transit timing variation, caused by an unaccounted for gravitational tug on the planet by an unseen body. The same technique has previously been employed to determine the masses of planets in systems with multiple...