Can we break the speed of light?

Prior to the day in 1947 when test pilot Charles E. "Chuck" Yeager broke the sound barrier for the first time, people argued it wasn't possible for a plane to fly that fast. So, perhaps we shouldn't be deterred by the part of Einstein's special theory of relativity that seemingly bars traveling at speeds faster than light.

That said, cracking the light-speed barrier is vastly more complicated than going faster than sound. The aircraft that Yeager used to break Mach 1, for example, didn't have to change form. But according to Einstein, an object that attains light speed would be converted to energy itself.

Nevertheless, as some physicists point out, there are nuances of Einsteinian physics that might permit faster-than-light travel. While an object can't exceed the speed of light in space-time, space-time itself can be warped and distorted, as if it were a stretched-out bed sheet. If a spaceship could harness something really powerful — like a bunch of super-dense matter from a neutron star — it might be possible to warp space-time enough to briefly pull two distant points together, the way that the edges of the bed sheet would come together if you dropped a heavy weight in the middle. Such warps in space-time — which are known as "wormholes" — in theory may occur naturally in some places, and a spaceship might be able to exploit them to travel enormous distances extremely quickly.

But it also may be possible to create such distortions in space-time. In 1994, Michael Alcubierre, a physicist at the University of Wales, published an article in which he proposed deliberately creating a contraction of space-time in the region in front of a spaceship, while simultaneously expanding the region behind it. The resulting distortion of space-time essentially would create a wave that would propel the spaceship forward at faster-than-light speed. Light in the space around the vehicle also would be propelled forward, but since it would move at the same speed as normal relative to the spaceship, Alcubierre argued that it would still be consistent with Einstein's theoretical framework.

Alcubierre's method for traveling faster than light would create some strange paradoxes. To an observer on Earth, the spaceship's acceleration would seem enormous, but an astronaut inside the ship would feel nothing at all, since the fabric of space-time itself would be moving while the ship seemingly remained motionless as it rode on the wave. (Imagine the astronaut as a traveler standing on a people-mover conveyor belt in an airport.) While an object moving at close to the speed of light would become incredibly heavy, according to Einstein, the astronaut in the spaceship using Alcubierre's warp drive would be weightless, and in theory, would be able to make the round-trip journey between Earth and the Andromeda galaxy — about four million light years — in the equivalent of a single day on Earth.