A lot? Bit? Want to know how much the Earth weighs?
- BBC World, @bbc_ciencia
To find out how much the Earth weighs, you have to take gravity into account and read this note to the end.
And how is gravity measured? The strength of the force that keeps the Moon orbiting the planet and us down to earth is determined by what physics calls “G”, the universal gravitational constant.
“Newton’s law of gravity describes the motion of planets and moons with amazing precision, and what we call Newton’s gravitational constant is what determines the scale, the magnitude of gravity,” explained to BBC Terry Quinn, Director Emeritus of the International Bureau of Weights and Measures.
“Small-scale gravity is very small, large-scale gravity is very, very large,” the expert said. Therefore, calculating a constant value was a challenge.
“The first person to measure it was a British scientist, Henry Cavendish, in the late 18th century.”
According to the scientists, Cavendish’s calculation had a margin of error of 1%.
Over the next 200 years, Quinn said, that measurement has become more and more accurate.
“At the end of the 20th century, we thought we were doing pretty well,” the scientist told the BBC, as the margin of error for the new estimates of the value of G was 0.001%.
The German 1%
But then the official German physics institution came up with a different result of 1%, which upset the scientists, who looked at the calculations and found no errors.
“So a lot of people around the world started doing measurements,” explained the expert, including the international weights and measures body.
“These measures take time. After 4 or 5 years the results started to come in and we didn’t confirm the German results, but we didn’t agree either,” Quinn said.
For this reason, new measurements and calculations are underway and experts in the field devote an entire issue of the scientific journal Philosophical Transactions of the Royal Society to Newton’s gravitational constant.
“It’s one of the fundamental constants in physics, and if we can’t measure it accurately, it indicates we’re not taking measurements correctly, and if it’s wrong, other things can be wrong. “, said Quinn.
However, despite doubts about the value of G, an estimate of the Earth’s weight is accepted by the International Bureau of Weights and Measures.
If you are still interested in knowing, it is around 7,000,000,000,000,000,000,000,000 kilograms.