How old is Earth?

If we consider the entire history of the Earth as one day, humans will only appear in the last few seconds before midnight. The few hundred thousand years of humanity represent only a tiny fraction of history. So how old is the blue planet and how do we find out this number?

Earth formed about 4.54 billion years ago, 10 million years after the birth of the solar system. After a giant cloud of gas collapsed to create the Sun, the remaining pieces of the cloud formed the planets.

However, the early Earth was completely different from the green world that humans know today. When it was born, the Earth was still molten due to the collisions that created the planet. Heavier parts, like iron, sink to form the core, lighter parts float to the surface. Ultimately, this leaves the Earth with many layers – core, mantle, crust.

As the solar system quieted down and fewer meteorites hit Earth, oceans formed and life appeared almost immediately. “Humans have not existed for most of Earth’s history, but cellular organisms have existed continuously for about 3.5 billion years,” said Mark Popinchalk, an astronomer at the American Museum of Natural History and the American Museum of Natural History. New York University, said. New research shows that this number may be even larger – 4.2 billion years.

Scientists collect information about the flow of time thanks to the ground. Rocks are key to determining Earth’s age and past conditions on the planet. Thanks to radioactive dating, scientists can use the amount of different radioactive elements to calculate the age of a rock. “However, rocks on Earth can be difficult because the planet is very active, very busy. Volcanism, weathering and geological processes mean finding rocks from Earth’s time extremely difficult to form,” Popinchalk said.

The Moon formed from a collision with the Earth when it was young, but does not have complicated plate tectonics like the Earth. Lunar rock samples from the Apollo era have helped refine estimates of the planet’s age, and new samples from missions like Chang’e 5 are adding to humanity’s understanding of the Moon’s history.

With neighboring planets like Mars, people can launch robots to collect rocks and then bring them back for analysis to determine their age. But how can we determine the age of distant planets orbiting other stars?

“The best way to learn about planets around other stars is to study the star itself. I guess the age of a star by looking at its rotation rate. Young stars rotate quickly while old stars rotate slowly. If I measure the rotation rate of a star with a planet attached, I can estimate the star’s age and use a similar number for the planet,” Popinchalk explains.

As we explore new worlds beyond our solar system, we are also learning in more detail how planets form. This will help people better understand the history of the Earth itself.