On Tuesday, October 20, a team in southeastern Spain lifted a block of stone out of a wall where it had been sitting for about twenty centuries. The block carries fragments of two lines of text. The letters of the main line are 23 centimeters (9 inches) tall, a little more than the width of […]

When an electron meets a positron, both vanish. Their mass turns into energy and nothing is left of either particle. That is the main reason positrons are so hard to study. There is no jar to keep them in, because the walls of any container are made of ordinary matter, and a single touch would […]