WASHINGTON (AP).- It’s one thing to make an object invisible, like Harry Potter’s mythical cloak. But scientists have made an entire event impossible to see. They have invented a time masker. Think of it as an art heist that takes place before your eyes and surveillance cameras. You don’t see the thief strolling into the museum, taking the painting down or walking away, but he did. It’s not just that the thief is invisible — his whole activity is. What scientists at Cornell University did was on a much smaller scale, both in terms of events and time. It happened so quickly that it’s not even a blink of an eye. Their time cloak lasts an incredibly tiny fraction of a fraction of a second. They hid an event for 40 trillionths of a second, according to a study appearing in Thursday’s edition of the journal Nature. We see events happening as light from them reaches our eyes. Usually it’s a continuous flow of light. In the new research, however, scientists were able to