Gravity makes apples drop, keeps clouds from flying into space, and stops people from floating up. (discovermagazine.com)
Instead, the speed of the outer stars remained high, suggesting that some unseen dark matter was providing the extra gravitational force needed to keep them from flying into space. (sciencemag.org)
They can not be used when flying into one of those countries or for any other international travel. (rismedia.com)