Atom smashers at a U.S. national lab have produced temperatures not seen since the Big Bang — 7.2 trillion degrees, or 250,000 times hotter than the sun's interior — in work re-creating the universe's first microseconds. The results come from the 2.4-mile-wide Relativistic Heavy Ion Collider at the Department of Energy's Brookhaven (N.Y.) National Laboratory. Since 2000, scientists there have hurtled gold atoms together at nearly the speed of light. These smash-ups heat bubbles smaller than the center of an atom to about 40 times hotter than the center of an imploding supernova. Scientists say the results have given them...