Multiple images of the same galaxy captured by the Hubble telescope.ESA / Hubble
Physics aims to know and describe all the phenomena of nature and the universe, formulate its principles and theories through mathematical language in order to predict and use their behavior.
By definition, all scientific theories can be refuted, but even when they are, on many occasions they cannot even be said to be wrong or false.
Rather, one must understand the usefulness of physical theories and their limitations.
Today we are talking about one of the best known physical laws, something that is already in our cultural heritage, the so-called "force of gravity", which does not exist as such according to the most advanced physical theories.
November 1915, Journal of the Prussian Academy of Sciences, page 315: Einstein presents the first of four articles on a groundbreaking new theory, the General Theory of Relativity.
From the title of the first article, it already identifies astronomy as the scientific branch where its postulates can be verified.
Basically, in these articles he tells us that what we still learn in school today about gravity is a children's story.
Well, we are going to be a little softer, it is an approximation since, in reality, the gravitational force does not exist, it is an illusion.
Newton's Law of Gravitation works very well to describe the movement of the Sun in the sky, the flight of airplanes or satellite communications, although in the latter case we are already beginning to see its limitations.
This law, which is more than 300 years old, gives us the value of the acceleration of a body subject to what it calls the gravitational force created by all mass.
But Einstein told us that gravity is not a real force and that what Newton taught us and today they ask in the EvAU does not work well either to describe movements at speeds close to that of light, nor when we use as a reference frame something that it has acceleration, which is basically… everything.
In reality, the gravitational force does not exist, it is an illusion
For Newton and for any mortal with basic knowledge of physics, something that is standing can only begin to move if a force is applied.
In an analogous way, something that moves, like the Earth around the Sun, only varies its movement, and breaks its inertia describing a closed orbit, if a force is exerted.
For General Relativity, the Earth does not break its inertia under the action of the gravitational force of the Sun, but the mass of the Sun (and everything that exists) curves space-time and our planet moves without flinching as that space allows. -time curved.
There are no forces between objects, they are fictitious forces the result of space-time being plasticine in the hands of the masses.
We return to page 315 of the Journal of the Prussian Academy of Sciences.
Einstein tells us about some of the implications of his new paradigm.
In a universe that is curved by the effect of mass (or energy), the photons created by stars, for example, follow paths affected by this curvature.
In principle we should be used to the light rays changing their trajectory, we can see it in a pool.
We see the bottom clearly when the water is completely calm.
But if the water moves, if there are waves, the rays of light coming from the bottom change direction and everything becomes blurry.
The difference with what Einstein proposes is that even if the light does not have to pass through anything, if there is only a vacuum through which the photons pass, space-time can be bent by a more or less close mass and the light rays are they move as dictated by that curvature.
Spacetime would be like a roller coaster, and nothing moving could separate itself from the curvature imposed by its rails.
This groundbreaking theory by Einstein was tried to prove in the years following its publication.
Sir Arthur Eddington, famous English physicist, devised an experiment carried out during an eclipse.
Eddington had to overcome setbacks to check Relativity, such as a World War, which he tried to object to in various ways, on religious grounds and also claiming the service he could do with his experiments on General Relativity.
But finally, on May 29, 1919, during a special eclipse, the longest in more than 500 years, Eddington went to an island in Africa called Prince to check what Einstein had written 4 years earlier.
Einstein proposes that, even if light does not have to pass through anything, spacetime can be curved by a more or less close mass.
In Principe it rained and rained but the sky was opened enough to take an image with a photographic plate through a telescope where stars of the constellation of Taurus were seen right next to the Sun. The stars are not seen during the day, the light of the Sun blinds us and prevents our optical telescopes from detecting them, they are much weaker than daylight.
But in an eclipse the great source of light is hidden and we can see the stars in the sky.
Eddington was able to observe several stars close to the then hidden solar disk, and measure their position relative to others farther away from the Sun. And what he found is that the position had varied by a very small distance, 1.75 arc seconds, the equivalent of power. detect the growth in one hour of the grass of the goal of a soccer field from the corner.
This difference was fully consistent with that predicted by Einstein's Theory of General Relativity.
The Sun, in effect, bends space-time and the light rays that pass near it vary their direction, with which the stars appear to be in a different position than the real one.
The natural phenomenon of gravity, we conclude, is much better described by Relativity, which states that it is not a force.
This demolishes what is described by Newton and that is still taught in schools.
The Newtonian view of gravity remains etched in the minds of students, so it is very difficult to make them understand the distortion of space-time or the concept of a non-absolute time later.
It is important to understand where concepts come from in science, and the contributions of the English physicist should not stop being taught, but without this supposing our current more precise vision of nature.
The gravitational force does not accompany us, much in spite of the Jedi, the thing is closer than what the Mandalorians say: "this is the way" (of gravity and space-time).
Pablo G. Pérez González
is a researcher at the Astrobiology Center, dependent on the Higher Council for Scientific Research and the National Institute of Aerospace Technology (CAB / CSIC-INTA)
Cosmic Void
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 1 atom per cubic meter, despite the fact that in our environment, paradoxically, there are quintillion 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
, researcher at the Center for Astrobiology;
Patricia Sánchez Blázquez
, tenured professor at the Complutense University of Madrid (UCM);
and
Eva Villaver
, researcher at the Center for Astrobiology
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