Can anything travel faster than light? Light moves about 300,000 kilometers per second. Things and information cannot go faster than this. In 2011, scientists said that tiny particles called neutrinos went faster than light. People were very surprised.

But later, the scientists found a problem with a cable. The neutrinos were not faster after all. However, faraway galaxies move away from us faster than light, because space itself is growing.

According to Einstein's theory of relativity, nothing that carries matter or information can travel faster than light in a vacuum. In 2011, however, an experiment called OPERA reported that neutrinos sent about 730 kilometers from CERN to an underground laboratory in Italy seemed to arrive about 60 nanoseconds too early. The team asked other scientists to help check for mistakes.

Later, they found that a fiber-optic cable had been loosely connected. After fixing the problem, they found no difference between the speed of the neutrinos and the speed of light. That said, some things can be "faster than light" in a sense. For example, very distant galaxies move away from us faster than light because space itself is expanding.

A cornerstone of Einstein's relativity is that nothing carrying matter or information can outrun light in a vacuum, which travels at about 300,000 kilometers per second. That principle appeared to be under threat in 2011, when the OPERA experiment reported that neutrinos fired roughly 730 kilometers from CERN to Italy's Gran Sasso laboratory had arrived about 60 nanoseconds earlier than light would have. Rather than claiming a revolution, the team invited others to search for errors. Painstaking checks then revealed problems including a loosely connected fiber-optic cable, and the corrected measurement, published in 2012, showed no difference from the speed of light within the margin of error.

Some phenomena nonetheless exceed light speed without violating relativity. Because space itself is expanding, galaxies beyond a certain distance recede faster than light, and a 2004 analysis clarified that some galaxies we can observe today fall into this category. In water, light slows to about three quarters of its vacuum speed, so high-energy particles can outpace it and emit bluish Cherenkov light, much as supersonic aircraft create a sonic boom. Even a theoretical warp drive, proposed in 1994, would require huge amounts of negative energy, which has never been found.