Speed of sound

The speed of light is the Universal speed limit – nothing can travel faster than light. In the vacuum (commonly denoted c), its exact value is 299,792,458 meters per second (around 186,000 miles per second). In other words, if you could travel at the speed of light, you could go around the Earth 7.5 times in one second.

It might seem blazing fast, but, in fact, when you think of the vast distances between the celestial objects in the Universe, the speed of light is actually torturously slow.

For example, Alpha Centauri, the nearest star system to the Sun is 4.3 light-years away from Earth – the light emitted from them takes 4.3 years to reach us.

Our Milky Way galaxy is around 150-200 thousand light-years in diameter.

That means sending messages back and forth on either side of the galaxy would take hundreds of thousands of years. This is one of the reasons that there may be no Kardashev Type III civilization in the Universe (a civilization that can control its own galaxy – you can think of it as Isaac Asimov’s galactic empire in the Foundation series).

As Douglas Adams p

how fast is light speed

how fast is light in mph