When NASA scientists think they’ve built something that breaks the laws of physics, do you take them at their word?

Folks have been buzzing about an “impossible” rocket thruster, one that looks like an air blaster you’d buy at Disney World and somehow generates thrust without propellant to push it forward, since forever. The so-called electromagnetic or EM drive makes headlines annually, but this year is different: an American team working on the drive released a peer-reviewed paper demonstrating that their prototype works, and a Chinese team claims that they’ve tested their own functional model. But physicists still aren’t sure about the results of these clunky copper cone tests, say nothing of their potential to lead to a Star Trek-esque warp drive as media outlets have suggested.

The American team’s fairly simple experiment went as followed: they attached the engine to a weighted metal bar attached to a rotating axle, kind of like tethering it to a weathervane. The main EM drive shell connects to electronics including a radio frequency amplifier, tuned to a specific frequency, causing particles of light called photons to bounce around inside. The whole setup goes into a vacuum, and an optical sensor points right at the drive to see whether the darn thing has moved or not. If the pendulum on the optical sensor moves forward in a certain way when the scientists hit the switch, they’ve measured thrust. The experiment was well-executed, says Ray Sedwick, Professor of Aerospace Engineering at the University of Maryland. “They were very careful setting [it up] and minimizing error,” he told Gizmodo.

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