If two people where traveling above the speed of sound in a ship, could they talk to each other?
in a ship or on its open deck?
Of course, two pilots of supersonic plane may talk to each other, as the air surronding them travel at the same speed as they do.
But you can't send a sound wave from one supersonic object to onother one travelling in parallel.
And - of course - no one may survive supersonic travel on an open deck: you couldn't breathe in such conditions.
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