How Fast is The Speed of Light?

Anyone that did basic physics must be familiar with this approximation of speed of light 3.00×10⁸ m/s, whose exact value is 299,792,458 meters per second. This is a unit of time that light could travel through a given substance.

From the world-famous physics equation postulated by Albert Einstein which is the theory of relativity

E=mc²
E = energy (measured in joules, J)
m = mass (measured in kilograms, kg)
where c= speed of light (squared) with units in meters per second, ms^-1

Albert Einstein in 1905 predicted that any object with mass could not travel as fast or faster than the speed of light. The theory is still correct to date. Though there are some extremely rare circumstances were some things were able to exceed the speed of light but since the object has no mass it does not count. Therefore Einstein prediction still stands.

Giving some perspective to the speed of light. It is 186,000 miles per second or 671 million miles per hour.

If any object could move at that speed it could circumvent ( go around) the earth 7.5 times in one second.

Even our beloved superhero in comics may find that speed hard to beat.

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The world fastest jet would circumvent the globe theoretically in 13.08 hours. This is just a rough calculation using 1,900 miles per hour. Since earth's equator is 24,870 miles. If we divide 24,870 miles by 1900 miles we have 13.08 hours. This is assuming no stops for refuel.

Though the first all around the world travel was done in by a BA Concorde on November 8, 1986, which covered a total of 28,238 miles in 29 hours 59 minutes.

So even the much-touted fastest manned aircraft, the North American X-15 rocket jet could not take on the speed of light. Its maximum speed was Mach 6.70 (about 7,200 km/h or 4520miles per hour) which is 6 times the speed of sound. That would still take a theoretical 5.5 hours to circumvent the earth.

Light vs Sound

From above it is easy to see that light travel faster than sound as you could see the X-15 conveniently beat the speed of sound. That explains the phenomenon during thunderstorms you see the lightning some seconds before you hear the sound. Both left at the same time but light been faster got to you first.



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The speed of sound in dry air at 20 °C is a sluggish 343 miles per second. Compare this to 768 miles per second, the speed of a fired bullet. That is why you never hear the bullet that kills you :)


This relationship between sound and light again is put to test in starting pistol used in races. You see the smoke before you hear the sound of the gun. Even the person firing it could notice that, but being so close may not be able to tell the difference.

Light Years

This is the time it would take light to travel in a year. It is used in measuring extremely long distances. This time difference actually means when we look in space we are actually looking at the past! Because it takes some time for the light to get to us here. The past may be in seconds, or in minutes if it is a further solar systems like the Sun.



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Looking at the above image, it means we can be looking at the Sun and it would explode. No one would notice this had happened until 8 minutes had passed. Wow!

Cool Story

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The Voyager 1 probe launched by NASA is the furthermost manmade spacecraft from earth launched on September 5, 1977. It has been operational for 14687 days (40 years 2 Months and 16 Days) as of November 21, 2017. It takes radio signals traveling at the speed of light 14 hours to reach it. It is 11.7 billion miles (18.8 billion kilometers) from Earth.

If you were to travel from Earth to Voyager 1 at close to the same speed light achieves, it wouldn't appear to take that long, however. Thanks to time dilation
According to the theory of relativity, time dilation is a difference in the elapsed time measured by two observers, either due to a velocity difference relative to each other or by being differently situated relative to a gravitational field.

Very little time would appear to pass from your perspective. And if you were to travel to the nearest star and back at near light speed it would appear that only a few seconds had passed. But as far as everyone on Earth would be concerned, you'd have been gone for 9 years. Pretty cool huh?

ref: 1,2,3,4.