We know the planet is rapidly spinning on its axis completing one full rotation every

day.

As we're gravitationally bound to the planet, and hurtling around in space, right along

with it.

We follow a circular path around the Earth at hundreds of kilometers per second.

So, just how fast does does it spin, and how fast are we rotating around on the surface?

Before we can talk speed, I've got to clarify how long a day is, it gets a little sticky.

We count a day as twenty-four hours.

This is the length of time it takes for the Sun to return to the exact same spot in the

sky as it was in the day before.

Astronomers call this a solar day. Here's where it gets a little complicated.

As we're taking a full year to go around the Sun, and changing our relative position to

our star, we have to add about four minutes every day to nudge the Sun back into the same

spot.

Which means if you look down at the Earth and watch it turn one complete rotation on

its axis, you'd count twenty-three-point-nine-three hours.

This is what's known as a sidereal day and is a more accurate measurement of the planet's

rotation. This is the amount of time we're going to use to calculate the speed the Earth

turns at.

Let's assume that you're standing on the equator, the halfway point between the north and south

pole.

Over the course of a sidereal day you'll travel along the entire circumference of the Earth,

and end back to your starting point.

We know the circumference of the Earth is fourty-thousand-and-seventy-five kilometers.

Divide twenty-three-point-nine-three hours into the circumference and you get

one-thousand-six-hundred-and-seventy-five kilometers per hour, or four-hundred-and-sixty-five

meters per second.

Every second that goes by, you've hurtled almost half a kilometer through space,

and you didn't even break a sweat.

This spinning is even causing you to lift off the Earth a little bit, like when you

spin a weight on a string.

That lifting force is about zero-point-three-percent of the force of gravity pulling you down.

If the Earth wasn't spinning, you'd weigh zero-point-three-percent more than you do

now.

As you travel towards the poles, your speed of rotation slows down.

Just imagine if you were standing straight upright on the North Pole, lining your own

axis up with the earth.

It would take you a whole day to turn around once, which is pretty slow even by sloth standards.

Our space agencies take advantage of the Earth's rotation to launch rockets.

The closer you are to the equator, the less fuel you need to get into orbit, or the heavier

payloads you can carry.

That's why Cape Canaveral in Florida is a great place to launch rockets.

Some clever people created Sea Launch, which blasts rockets off from an ocean platform,

right at the equator.

Which is even better at maximizing your launch benefits of planetary rotation.