Andriy Popov/Alamy
Why do our knuckles and joints make a popping sound when cracked? Does it do us any good or harm?
Nick Vale
Hartley Wintney, Hampshire, UK
I have no idea why popping knuckles makes this noise, but it was established it does no harm back in 1998, an achievement for which Donald Unger won the Ig Nobel medicine prize in 2009.
Every day for 50 years, Unger cracked the knuckles of his left hand, but never his right, and ultimately observed no difference in the function of either hand.
David Nye
Eau Claire, Wisconsin, US
Pulling on the end of…
