Bacteria, teeth, the Sun and moving trains
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Bacteria on the teeth, the age of the Sun and what's it called when you're on a train and another train moves and you think it's your train that's moving? Dr Karl and Dr Rhod wrestle with your science queries. \\nYou can send your questions to UpAllNight@bbc.co.uk anytime, just put Dr Karl in the subject line.
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