Our home is planet Earth. How old is it? At what speed does it revolve around itself? And around the sun? Questions and answers to better understand our common home.
For us humans, the Earth has always existed and has always included everything that surrounds us. Nevertheless, our world is nothing more than a finite 'body', like all the other stars and planets we see in the sky, with an exact mass, size and, of course, origin. But then how old is the Earth? And how much does she weigh? Let's open her identity card!
The place where we live, where we dream, hope and get upset is very young compared to the universe, but for us it is definitely old. Of course, because the age of the Earth is about 4.5 billion years, given that figure, 50 million years more or 50 million years less is no longer decisive, because it is a fraction of a second. Actually, calculating the age of the planet is not an elementary task and geologists - scientists of the Earth - can only guess estimates based on analysis of the oldest rocks, which of course cannot give an exact answer, because as we know - nothing lasts forever.
Everything dies and something new emerges in its place. Therefore, there is no guarantee that the material studied has been here since the beginning of time and not appeared, for example, a couple of billion years ago. After all, the Earth's rocks are cyclically eroded by continuous planetary geological movements (e.g. volcanism).
Planet Earth, the speed of the Earth's rotation and its dimensions
The Earth's radius - corresponding to the equator - is 6,378 km. On the other hand, the total surface area is almost 510,100,000 km².
We don't realise it, but the planet Earth we live on rotates at a dizzying speed. As we know, it takes the Earth about 24 hours - 23, 56 minutes and 4 seconds, to be precise - to make one complete revolution around itself, and to do so it spins at an average speed (it is not constant) of about 1,600 km/h.
However, this speed is calculated from the equator - the planet's maximum circumference: because the planet Earth is a ball (more precisely, a geoid flattened at the poles), the rotation speed varies depending on where it is located. At our latitudes, for example, we move a little slower, about 1,180 km/h, while at the poles we remain virtually motionless. And if you're not impressed by this speed then what do you say to that -
As Copernicus and Galileo taught us, the planet Earth not only revolves around itself, but more importantly, it makes a revolution around the Sun, our star. At what speed does this movement occur? Since a complete revolution takes 365 days, this means that the average orbital speed is about 107,000 km/h, plus or minus 30 km per second.
Of course, we earthlings do not notice this insane speed at all, because, being integrated into the system, we are "travelling" along with our planet. It is like sitting in an aeroplane with all the windows covered with curtains: the passenger seems to be standing absolutely still.
The planet Earth revolves around itself and also around the Sun. Everything rotates... And if everything rotates, why aren't we falling? I know you've all asked yourselves that question. And it's not easy to answer, you know! The laws of the Universe are so strange, mysterious and difficult to explain that trying to do it in a few simple words is an impossible task.
The simplest explanation is the force of gravity, which is essentially the attraction that exists between bodies. The Earth has such a strong attraction on all the objects that are in it that it keeps us on the ground and prevents us from flying off into space. For clarity, try looking inside a washing machine when it begins to spin laundry, notice how your shirts, trousers and other clothes, while spinning the drum "stick" to its walls? There's your answer.
Not only that: since people, animals and everything on Earth rotates at the same speed as the planet (rotational motion), and we move in space with it, we are not aware of either motion. Except that from time immemorial, every day is followed by night. And so it will be until the end of time.
The density of the Earth and its weight
Although the planet Earth is by no means the biggest in the solar system, it is not exactly... featherweight: it weighs almost 6 billion tonnes. Of course, this figure was not arrived at by constructing colossal weights, but by using complex calculations that take into account the laws of physics and the size of the planet.
What about density? it is a physical concept that is not easy to understand. Being the ratio of mass to the volume of matter, it basically tells us how much matter exists in a certain part of the volume.
The Earth, for example, has a density of 5,514 kg/m³, making it the densest planet in the solar system. By comparison, Saturn's density is only 687 kg/m³, which is less than that of water. So, if we were to take a small piece of Saturn and a jug of water of the same volume in the lab, the liquid in the jug would be denser (therefore containing more matter) than the small piece of Saturn!