But these temperatures are the most tenuous of states. The enemy is stray heat from outside. The researchers at Cornell and Florida have constructed whole rooms and buildings to shield their refrigerators from heat, which sneaks in as radio waves, or from cosmic background radiation, or from anything that causes vibration: trucks on the freeway, distant earthquakes, slamming doors. Each creates minute vibrations that jar the super-cold atoms and cause them to bump, raising temperatures.
Yet no matter what the scientists do they will never quite achieve absolute zero. The closer they get, the larger the relative effect of the slightest amount of heat that gets in. "We can get close, very close, but it will always be beyond us," said Richardson of Cornell. And that is part of its allure, he said.