Ever since we first looked up at the night sky and saw the glittering tapestry of distant stars, humanity has wondered about what else might be out there. As we learned more about the Universe, our curiosity only increased. We discovered not just the thousands of stars visible to the naked eye, but hundreds of billions within our own Milky Way, and a collection of an estimated trillions of galaxies within our observable Universe. We now know that most of these stars likely contain a system of planets orbiting them, and many of those planets contain properties — like temperature, size, mass, and their atomic compositions — that are very similar to Earth.

Unfortunately, our hopes of visiting and exploring these worlds face a tremendous obstacle: the limitations of the speed of light. While it’s theoretically possible to accelerate objects, even macroscopic ones, close to the speed of light, the laws of physics not only prevent us from achieving or surpassing that speed, but they damn us to the severe experience of time dilation. Even if we were to get in a spaceship and travel at near-light speeds, everyone back at home would age spectacularly while we undertook our interstellar journey.

There was only one potential way out: warp drive, or taking a “short-cut” by severely curving the fabric of spacetime. Long thought impractical, the physics behind this possibility was worked out by Miguel Alcubierre in 1994, and the only requirement was something that anti-gravitated: something like “negative energy” or “negative mass.” With the recent measurement that antimatter falls down in a gravitational field, humanity’s greatest hope for practically achieving our warp drive dreams just suffered a massive blow. Here’s the science behind the amazing, but sobering, result.

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