Your experience of time is relative because it depends on motion – more specifically, your speed and acceleration.

In this case, space-time is expanding, but the material in space-time is still traveling within the bounds of light speed. Related: A diagram of the visible color spectrum.

The speed of light is a fundamental constant, approximately 299,792,458 meters per second. It's the same for all observers and hasn't changed measurably over billions of years. Nothing can travel ...

In this thought-provoking journey to the outer limits of the universe, we explore the fascinating concept of traveling near the speed of light. What would happen if humanity sent a generational ...

Nowadays, the speed of light is used to define units of length, so its value is fixed; humans have essentially agreed the speed of light is 299,792.458 kilometers per second, exactly.

Unfortunately, reaching this lofty speed turns out to be impossible. "You cannot go at the speed of light, given that you have a finite mass," Pravica said.

Ultimately, they estimated that the jet was zooming directly at Earth at around 99.95 percent the speed of light. That’s very close to the speed of light, but not quite faster than it.

Then you just need the speed of light to calculate the distance. There is, of course, a practical issue: Light travels really fast. Its speed is 3 x 10 8 meters per second.