It may not seem like it to us, but our planet is moving at incredible speeds. In fact, every hour, our planet moves approximately 107,000 km (67,000 miles) in its orbit around the Sun. But how do we know this? After all, it’s not like there is a great cosmic radar that we can look at in order to clock our speed.
It may seem like a rather difficult question to answer, but really, it only requires a little knowledge of geometry.
To begin with, we know that the Earth completes one orbit every 365 days. Well, technically, a year is just a little longer than this (in truth, a years is actually 365.25 days long). That’s why, every four years, we have an extra day (we’re playing a bit of catch up with those quarter days). But to make things simple, let’s just round down to a nice 365.
We also know that our planet is about 150 million km (some 93 million miles) from the Sun, and that it travels in a near-circular orbit.
Technically, the Earth has an elliptical orbit. But this really doesn’t change things too much. You see, eccentricity (how much something varies from a perfect circle) is measured according to a scale that ranges from 0 to 1. And in this case, 0 is a circle and 1 is a very stretched out ellipse. The Earth has an eccentricity of just 0.016.
So, to make things easier on ourselves, let’s just say that it is actually a perfect circle.
And, if you remember your geometry, to figure out the circumference of a circle, you use π X the diameter of the circle. Since π goes on for infinity, it gets rounded to 3.14
So we double the radius to get the diameter (93 million + 93 million = 186,000,000), and then we multiply that by 3.14
- 186,000,000 X 3.14 = 584,040,000
That gives us the distance of the circular path that the Earth follows as it travels around the Sun. So we now know that our planet travels about 941 million km (585 million miles) each time that it completes an orbit.
In order to know how far the planet travels each day, we just divide the previous solution by the number of days in a year (365).
- 585,000,000/365 = 1,602,000
So the Earth travels roughly 2,578,000 km (1,602,000 miles) each day.
To make the figures even more meaningful, divide that by the number of hours in a day (24).
- 1,602,000/24 = 67,000
So. This means that the Earth travels just about 107,000 km/h (67,000 mph). And, regardless of whether you use miles or kilometers, that’s pretty fast.