Empty space might feel hot to a traveler zipping through at a rapidly increasing clip — or so some physicists predict. And a new experiment provides a hint that they might be right.

That idea, known as the Unruh effect, seems to be supported by an analogous effect that appears in a tank of rippling water. Patterns in the waves, when analyzed as if seen by an accelerating observer, appear to re-create the expected signature of the effect, researchers report September 7 at arXiv.org. If it holds up to further scrutiny, the result would mark the first time a version of the Unruh effect has been spotted.

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