Jens Ickler/Alamy
How do you check the accuracy of an atomic clock “that will lose less than 1 second every 40 billion years”, as per a recent 鶹ý article?
John Grant,
Sydney, Australia
Matthew Ashmore/Alamy
Why, if an unfastened duvet cover is put into a washing machine, does it bag up all the other items in there to be washed?
Anne Hayes,
Forest of Dean, Gloucestershire, UK
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