Thoughts in Free Fall

In similar fashion to his earlier theory, gravity came to Einstein's attention in the form of a thought experiment. He imagined someone falling off the roof of a house while simultaneously dropping an object (say a box of tools). As the unfortunate man descends, he notices that it remains right next to him. Although the dropped object is falling independently, he can reach out and grab it whenever he wants. Except when he hazards to look down, his situation seems to him exactly as if he had...

Lighter than Weightless

How could something weigh less than zero pounds Could such strange fruit exist Are there watermelons somewhere in the universe that would levitate from grocer's scales Are there negative mass boxes of chocolate-covered cherries that would actually remove poundage with each serving After enough bites, could we float like Mary Poppins Despite numerous experiments, scientists have yet to detect particles with negative mass. Even positrons, the oppositely charged antimatter counterparts to...