A new test of water ripples supports the idea of quantum heat in a vacuum

This in-the-lab analog of the Unruh effect matches expectations for accelerated motion in space

empty space

HEAT WAVE  Accelerating at a high rate could make empty space seem hot, according to an idea called the Unruh effect. Scientists may have spotted signs of an analogous phenomenon in ripples of water.

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Empty space might feel hot to a traveler zipping through at a rapidly increasing clip — or so some physicists predict.