On Wed, Apr 19, 2017 at 10:59:24PM -0400, Richard Aiken wrote: > While it may be inaccurate in it's wording, what the article actually said > was that when the atoms were released from the supercooled laser trap, they > expanded and "some displayed negative mass." Yes, it means that for the purposes of that particular experimental setup, they behaved in a very limited way as something of negative mass would have behaved. - Tim