Deep space may provide hidden sources of energy, such as dark matter, for fueling futuristic spacecraft. Before we reach that stage, however, a new experimental engine suggests it’s already possible to tap into deep space as a potential energy source—albeit on a smaller scale that likely won’t support interstellar travel.

Indeed, the purpose of the new engine, described in a Science Advances paper published on November 12, is far less ambitious—but it still marks an important step forward. So far, its primary purpose is to ventilate greenhouses and other buildings. Known as a Stirling engine, the simple device converts differences in heat to mechanical energy.

What’s special about this particular engine, however, is that it uses the depths of space to provide the required chill. The

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