Long-time Slashdot reader fahrbot-bot quotes Live Science:
When you touch a hot surface, you’re feeling movement. If you press your hand against a mug of tea, warmth spreads through your fingers. That’s the sensation of billions of atoms banging together. Tiny vibrations carry thermal energy from the water to the mug and then into your skin as one molecule knocks into the next, sending it careening into a third — and so on down the line.
Heat can also cross space as waves of radiation, but without radiation, it needs stuff to pass through — molecules to bang into other molecules. Vacuums have no ‘stuff’ in them, so they tend to trap heat. In Earth’s orbit, for example, one of the biggest engineering challenges is figuring out how to cool down a rocket ship.
But now, researchers have shown that, on microscopic scales, this isn’t really true. In a new paper published Dec. 11 in the journal Nature, physicists showed that little vibrations of heat can cross hundreds of nanometers of empty space. Their experiment exploited an uncanny feature of the quantum vacuum: It isn’t really empty at all.