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Veritasium
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These resources have been reviewed and selected by STEM Learning’s team of education specialists for factual accuracy and relevance to teaching STEM subjects in UK schools.
World's roundest object
This video shows the roundest object in the world – one kilogram sphere of silicon. In 1799, the definition of a kilogram was the mass of one litre of water, at 4 degrees Celsius. As of 2016, the kilogram is defined by the mass of a platinum-iridium sphere, located in Paris, called the International Prototype Kilogram. In a perfect crystal sphere of silicon, the number of atoms in the sphere can be calculated using a laser to measure the diameter. The number of atoms in the sphere could then be used to define Avogadro’s number, which in turn could define the kilogram.
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