The first day of skating, my daughter told me that the most important thing is to learn how to fall.
With my professional deformation, I thought: look, skating is similar to physics, where the most important and most complicated thing is to learn how things fall.
And it is that the key to our being here, to the existence of our planet, our Sun, our galaxy, is that part of the material that makes up the universe has 'fallen' to a certain place.
I put that verb in quotes because the concept of falling is not too easy on a cosmic scale.
I explain it, although this is one of the great questions that humanity has asked itself for millennia and today astrophysicists ask themselves and still (I am optimistic) we do not understand it well.
The subject is so complicated that it will give me several weeks, and not even then.
I start today by talking about why things fall?
And the world, will it end in fire?
Let's start with the most common, which might seem the easiest to us
why do things fall on Earth?
Aristotle said: "Everything tends to what is natural and a stone falls to the ground because they are of a similar nature."
You will say, millennia later: easy, due to its weight and that is precisely what the RAE says, falling is "moving from top to bottom due to the action of one's own weight."
But if they already have a little more knowledge of physics, they will say: it falls due to the effect of gravity or the gravitational force associated with the mass of the Earth.
All three answers are correct to some extent, although they do not fully describe reality and, in fact, the most advanced physical explanation today goes beyond those concepts of nature, weight and force.
But I don't want to stop there, never better said, because I want to see how falling things stop.
What I want now is to move forward in time and wonder what happens after something starts to fall.
Under the effect of gravitational acceleration, every body increases its speed.
Leaving aside the effects of air resistance, which have to slow down objects (in a different way depending on their shape), a body, in what is called free fall, goes faster and faster.
Let's leave this hanging for a moment and move on to another concept.
The history of the universe is like a George RR Martin novel, a song of ice and fire eternal (until today).
Only if there are icy gas clouds (in the sense of very cold, with temperatures of -200 degrees Celsius or less) with hydrogen can stars appear, which are superhot entities compared to that primordial gas.
The stars die and their material, which includes elements such as oxygen, phosphorus or iron, which have been synthesized in their interior, cools down again, actually being surrounded by a cosmos that has an average temperature of about -270 degrees Celsius. close to absolute zero (less than 3 degrees above).
These elements once again form cold clouds that warm up again and give rise to planets with temperatures that we consider benign for our lives.
cold and hot,
Temperature is actually a measure of the speed of the air molecules in our atmosphere or of the atoms in the gas clouds that make up stars.
And here we introduce what we needed to continue our story that things fall.
Things fall, they go faster and faster, so their temperature increases.
And if the temperature of a gas increases, how can cold clouds form?
Without cold clouds there can be no areas where the material becomes denser, and this is necessary to form stars or planets.
Returning to Earth, what falls gains speed —kinetic energy it is said— and the final result, whether it knows how to fall like the skater or not, is to stop its movement with a crash against the planet's surface.
Unless its energy is high enough, the result of the collision will be that all that energy it was carrying will be converted into deformation, vibration (and therefore sound), heat... That is, into energy transfer to the atoms of the ground and of the falling object, that they will move faster, so much so that perhaps they can no longer macroscopically account for a solid, but instead become a liquid (where the atoms or molecules move more) or even a gas.
Once we are clear about what it means to fall on Earth, let's apply it to the universe.
For stars to form, and planets and life along with them, there must be cold clouds in which the density increases to what we see on the Sun or our planet.
For these clouds to form, the material must fall to a certain place, because the universe as a whole is much less dense than the clouds that give rise to stars.
Imagine the atoms falling due to the effect of gravity, although it is important to note that there is no up or down that helps to understand the word “fall”.
But the gravity associated with what?
And if the atoms fall each time they will have more speed, higher temperature, so how do they cool down to form the clouds that give rise to stars?
Because there is no planet surface for them to stand on.
There are even more questions:
Does all matter fall equally into those clouds to form stars or are there things that fall faster?
Does matter fall in the same way at stellar scales as it does at larger scales, similar to the size of galaxies?
As you can see, many more questions than answers, I already warned that the subject is the most complicated in the world, in fact, in the universe, some of us dedicate our lives trying to understand it.
is a section in which our knowledge about the universe is presented in a qualitative and quantitative way.
It is intended to explain the importance of understanding the cosmos not only from a scientific point of view but also from a philosophical, social and economic point of view.
The name "cosmic vacuum" refers to the fact that the universe is and is, for the most part, empty, with less than one atom per cubic meter, despite the fact that in our environment, paradoxically, there are quintillions of atoms per meter cubic, which invites us to reflect on our existence and the presence of life in the universe.
The section is made up of
Pablo G. Pérez González
, a researcher at the Center for Astrobiology, and
, a researcher at the Center for Astrobiology.
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