How Much Does The Earth Weigh?
QUICK ANSWER
Earth has a mass of about 5.97 sextillion metric tons, or roughly 13 septillion pounds. Technically Earth doesn't have weight in the usual sense; it has mass. Weight requires gravity from another body, but mass is intrinsic to the object itself.
Earth doesn't sit on a scale. Asking how much Earth weighs is really asking how much mass it has, and that question can be answered very precisely. The number itself is mostly incomprehensible, but the way scientists figured it out is a great story.
What is Earth's mass?
According to NASA, Earth has a mass of approximately 5.97 × 10^24 kilograms, or about 5.97 sextillion metric tons. In imperial units, that's roughly 13 septillion pounds (1.3 × 10^25 lbs). To put it in some perspective, Earth is about 81 times more massive than the Moon, but Jupiter is about 318 times more massive than Earth. Of the rocky planets, Earth is by far the most massive.
How do you weigh a planet?
Not by putting it on a scale. Earth's mass was first calculated in 1798 by British scientist Henry Cavendish using gravity. He measured the tiny gravitational pull between two lead balls in his lab and used that to figure out the gravitational constant (G). Once G was known, scientists could combine it with Earth's known gravity (9.8 m/s²) and radius to solve for Earth's mass. The math is exact: Earth's mass equals (gravity × radius²) divided by G. The number has been refined over the centuries but the basic approach is the same.
Why does Earth have mass instead of weight?
Weight is a measure of gravitational force pulling on an object. To have weight, something has to be in a gravitational field from another body. Mass is intrinsic; it's the amount of matter in an object, independent of where the object is. A 150-pound person on Earth has 150 pounds of weight but about 68 kilograms of mass. On the Moon, the same person would weigh only 25 pounds, but their mass would still be 68 kilograms. Earth has plenty of mass, but it doesn't have a meaningful weight because it isn't sitting in another planet's gravity.
Is Earth getting heavier or lighter over time?
Net losing slightly, by very small amounts. Earth gains about 40,000 tons of mass per year from dust and meteorites that fall through the atmosphere. It also loses mass, mostly hydrogen and helium atoms stripped from the upper atmosphere by solar wind, totaling around 95,000 tons per year. The net loss is negligible compared to Earth's total mass. It would take billions of years for these processes to make any measurable difference.
Earth has a mass of about 5.97 sextillion metric tons, calculated centuries ago using a clever experiment with lead balls and almost no modern equipment. The number is precise, the method is elegant, and the planet is steadily but imperceptibly losing a small amount of mass to space.
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