We explain what gravity is, its discovery and how it can be measured. We also explain its characteristics, formula and more.
Gravity is one of the four known fundamental interactions of matter.
What is gravity?
The force of gravity (or simply gravity) is the force by which bodies endowed with mass attract each other in a reciprocal manner. Its greater or lesser intensity depends on the mass of the bodies. It is one of the four known fundamental interactions of matter and can also be called “gravitation” or “gravitational interaction”.
Gravity is the force we feel When the planet Earth attracts the objects that surround it to its centerthe same one that makes things fall. It is also responsible for the planets orbiting around the Sun, attracted by its mass despite the vast distances that separate them from it.
The intensity of this force It is related to the speed at which the planets orbit.: Those closest to the Sun are faster and those further away are slower. This indicates that gravity is a force that, although it affects very massive objects even at great distances, its intensity decreases as the objects move away from each other.
See also: Magnetic field
How was gravity discovered?
The first theories about gravity were from the Greek philosopher Aristotle.
From the earliest times, human beings understand that Things fall when no force is applied to them to hold them.
However, the formal study of that force that pushes them “down” was not carried out until the 4th century BC. C, when the Greek philosopher Aristotle outlined the first theories.
In its universal conception, the Earth was the center of the universe and, therefore, the protagonist of an invisible force that attracted everything towards it. This force was called during Roman times “you gravitate”linked to the idea of weight, since in those times there was no distinction between the weight of an object and its mass.
These theories were later revolutionized by Copernicus and Galileo Galilei. However, it was Isaac Newton who proposed the term “gravitation.” The first formal attempts to measure gravity and develop a theory, which was called the Law of Universal Gravitation, were also made then.
How is gravity measured?
The force of gravity It is measured in relation to its effectsthat is, to the acceleration that it prints on the objects mobilized by it, for example, those that are in free fall.
On the surface of the Earth, This acceleration has been calculated at about 9.80665 m/s2 This figure may vary minimally depending on the geographical location and the altitude at which we are.
Gravity measurement units
The acceleration of bodies attracted by another of greater mass is measured.
Gravity is measured with two different magnitudes depending on what you want to study:
- Force. When measured as force, Newtons (N), unit of the International System (SI) that honors Isaac Newton. The gravitational force is the force that a body feels when it is attracted to another.
- AccelerationIn these cases, the acceleration obtained by a body when it is attracted by another is measured. Since it is an acceleration, the unit m/s2 is used.
It is important to note that given two bodies, The gravitational force that each one feels is the same due to the principle of action and reactionWhat is different is the acceleration because the masses are different. For example, the force that the Earth exerts on our body is equal to the force that our body exerts on the Earth. But since the mass of the Earth is much greater than that of our body, the planet does not accelerate at all; it does not move.
Gravity formula
The gravitational force can be calculated through different formulas, which vary depending on the specific physical approach with which it is approached: classical mechanics, relativistic mechanics or quantum mechanics. Each one takes different elements into consideration and deals with a specific perspective.
For example, according to Newton’s laws, gravity acting between two bodies It is directly proportional to the product of their masses (m) It is inversely proportional to the square of the distance (d) that separates them:
Fg = m1.m2/d2
Gravity in classical mechanics
Gravity is calculated using Newton’s Law of Universal Gravitation.
Gravity in classical or Newtonian mechanics obeys Newton’s empirical formulationswhich deals with forces and physical elements within a necessary fixed frame of reference. This gravity is valid in inertial observation systems that are considered universal for the purposes of the study.
According to classical mechanics, the gravitational force is determined as:
- An ever-attractive force.
- Which presents infinite scope.
- That presents an associated force of a central type.
- Which is more intense the closer the bodies are and weaker the closer they are.
- It is calculated using Newton’s Law of Universal Gravitation.
This law of nature It has very important implications for the study of many natural phenomena.both in the world and in the universe. Newton’s theory of gravitation was and is considered today as it was stated by the English physicist. However, the most complete theory of gravity was introduced by Albert Einstein in his famous theory of general relativity.
Newton’s theory is an approximation to Einstein’s, which is essential when studying regions of space where gravity is much greater than what we experience on Earth.
Gravity in relativistic mechanics
According to relativistic mechanics, gravity is the result of the warping of space-time.
Einstein’s relativistic mechanics broke with Newton’s theory in certain areasespecially those applicable to spatial considerations. Classical laws lose effectiveness at distances such as those between stars and without a universal and stable reference point, given that the entire universe is in motion.
According to relativistic mechanics, the force of gravity does not exist as an interaction that simply appears when two massive objects are close to each other, but rather It is the result of the geometric deformation of space-time caused by the large masses of the stars. This means that gravity even affects time.
Gravity according to quantum mechanics
There is currently no quantum theory of gravity.This is because the physics of subatomic particles that quantum physics deals with is very different from that of very massive stars and a theory of gravity that unites both worlds (quantum and relativistic) has not yet been found.
Theories have been proposed that attempt to do so, such as loop quantum gravity, superstring theory or the twistor theory. However, none have been validated.
Discovery of gravitational waves
Gravitational waves can cause black hole mergers.
In February 2016 The detection (for the first time in history) of gravitational waves was announced, which seems to confirm Einstein’s theories.
It is estimated that these waves were produced by massive events that occurred in space billions of light years away our planet, such as black hole mergers or massive supernovae. This discovery was made at the LIGO laboratories in Hanford, Washington, and Livingston, Louisiana, USA.
Weightlessness
Weightlessness is the absence of gravitational attraction.
Weightlessness is the state of a body experiencing weightlessness. absence (real or apparent) of gravitational attraction about himself. This happens, for example, with astronauts in outer space.
Examples of the force of gravity
Some examples of the action of the force of gravity are:
- The acceleration of an object in free fall. The gravitational force that the Earth exerts on it acts on an object in free fall and, as a consequence, the body has an acceleration (that of gravity) and, therefore, its speed increases as it descends.
- An object thrown in a straight line. In this case, the action of gravity (which pushes the object downwards) causes its path, originally in a horizontal direction, to curve and result in an oblique one and causes the object to finally fall to the ground.
- The orbit of the planets. The planets orbit around larger stars, as happens with the planets in the Solar System around the Sun. The same happens with moons and artificial satellites around the planets.
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