What is the mass of the Earth?

The Mass of Earth: A Staggering Number You Might Not Be Able to Imagine

Hello! The mass of Earth is a fascinating astronomical question. When we usually talk about "weight," we use units like "jin" or "kilograms," but Earth's "body weight" is in an entirely different league.

Currently, the scientifically accepted mass of Earth is approximately:

5.972 × 10²⁴ kilograms

Just How Big is This Number?

You might not have a clear idea of what a number with an exponent like that means, and that's completely normal. Let me write it out for you to fully grasp it:

5,972,000,000,000,000,000,000,000 kilograms

That's right, it's 5972 followed by 21 zeros!

This weight is utterly unimaginable in our daily lives. Even if you were to add up all the people, all the buildings, all the mountains, and all the oceans on Earth, it would still only be an insignificant fraction of this enormous number.

How Do Scientists "Weigh" the Earth?

You're probably curious: since we can't exactly put the Earth on a giant scale, how did we arrive at this number?

In fact, this is largely thanks to the famous physicist Isaac Newton and his discovery of the Law of Universal Gravitation.

This law tells us that any two objects with mass exert an attractive force on each other. The magnitude of this gravitational force depends on the masses of the two objects and the distance between them.

Simply put, scientists do it this way:

Measuring Gravity: We know the strength of Earth's gravity because it determines the "weight" of everything around us. For instance, a standard 1-kilogram mass experiences a gravitational force of approximately 9.8 Newtons on Earth's surface.
Measuring Earth's Radius: We also know how large Earth is, specifically its radius (approximately 6,400 kilometers).
Applying the Formula: By plugging these known values (the object's mass, the gravitational force it experiences, and Earth's radius) into Newton's Law of Universal Gravitation formula, we can, much like solving a math problem, calculate Earth's total mass.

Nowadays, we can also use more precise methods, such as observing the orbital trajectories of artificial satellites. Satellites are able to orbit Earth because they are "pulled" by Earth's gravity. How fast they fly and how high their orbits are directly relate to Earth's mass. By precisely measuring satellite data, we can obtain a highly accurate mass for Earth.

A Fun Little Fact

You might assume Earth's mass is constant, but it actually undergoes subtle changes every year:

Increase: Approximately 40,000 tons of space dust and meteorites fall onto Earth each year, "adding weight" to the planet.
Decrease: At the same time, some lighter gases in Earth's atmosphere (such as hydrogen and helium) escape into space due to high energy, causing Earth to lose about 50,000 tons of mass annually.

So, when all is said and done, our Earth is actually subtly "losing weight" by about 10,000 tons each year! However, there's absolutely no need to worry; compared to Earth's incredibly vast total mass, this change is less than a drop in the ocean and entirely negligible.