One of the most controversial stories in science right now is the EM Drive, a hypothetical new type of spacecraft engine that seems to break the laws of physics. While many scientists are highly skeptical the device even works, it's been tested multiple times, including by a team of NASA scientists, and some tests seem to indicate that it does work.

So what exactly is going on? What is the EM Drive exactly, and how could it be breaking the laws of physics? Is there another explanation? Probably. PBS Space Time explains:

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