What is superluminal speed?

Superluminal speed refers to the concept of traveling faster than the speed of light. In a vacuum, the speed of light is precisely 299,792,458 meters per second, and it is considered the maximum speed at which energy, information, or matter can travel according to Einstein’s theory of relativity. The term "superluminal" itself comes from the Latin words "super" meaning above or beyond, and "lumen," meaning light. Thus, superluminal speed is any speed that exceeds the speed of light in a vacuum.

However, according to the currently accepted physical laws, particularly those of special relativity, an object with mass cannot accelerate to the speed of light within normal spacetime. This is because, as an object's speed approaches the speed of light, its relativistic mass increases, requiring an infinite amount of energy to reach or exceed the speed of light. Therefore, objects with mass cannot achieve superluminal speeds.

It's worth noting that there are some phenomena in physics that might appear to involve superluminal speeds, such as the phase velocities of certain waveforms or the apparent faster-than-light movement seen in some astronomical observations (like the jet projections from quasars). However, these do not involve actual material objects traveling at superluminal speeds and do not violate the principles of relativity.