In space exploration, astronauts face zero gravity.
Gravity is a physical force that the Earth exerts on all bodies towards its center. It is also about the force of attraction of bodies due to their mass .
Gravity - a term that comes from the Latin gravĭtas - is linked to weight , which is the force of gravity exerted by the mass of the planet on all objects that are within its gravitational field. The weight of the same body can vary on different planets if their mass is different from the mass of the Earth.
Gravity characteristics
The English physicist, mathematician, philosopher and inventor Sir Isaac Newton was the one who proposed the law of universal gravitation or theory of gravity . Newton stated that every object that has mass exerts a gravitational attraction on any other object with mass, beyond the distance between them. The greater the mass, the greater the force of attraction; On the other hand, the closer the objects are, the greater the force of attraction.
However, we must not forget the fact that throughout history there have been other scientists and researchers who have also left their mark on the concept of gravity. This would be the case, for example, of the German physicist Albert Einstein , who is known precisely for his theory of general relativity .
In 1915 , Einstein presented this theory to the scientific community, which we could basically say is a reformulation of the term gravity. Specifically, with that one what he did was establish that gravity, more than a force of attraction, is a sample of the distortion or curvature of space-time geometry. A distortion that is clearly influenced by the set of objects that are part of it.
In short, gravity is one of the fundamental physical interactions (along with the electromagnetic force, the weak nuclear force and the strong nuclear force).
Gravity produces the movements that can be observed in the universe, such as the Earth 's orbit around the Sun and the Moon 's orbit (a natural satellite) around our planet. That is why it is not only a phenomenon of interest for physics, but also for cosmology, astronomy and astrophysics.
We must emphasize the relevance of gravity in the description of celestial movements. This is due, above all, to the fact that it is an attractive force that, under certain circumstances, acts as a repulsive force. This is the case with dark energy , which would be responsible for the acceleration of universal expansion. Dark energy (which, as its name indicates, is a form of energy) should not be confused with dark matter , although both make up much of the mass of the universe.
String theory, presented as a theory of everything, offers a quantum explanation of gravity.
Quantum mechanics
Quantum mechanics , also mentioned as quantum physics , is dedicated to the analysis of nature on a small scale, studying the interactions of subatomic particles and atomic systems with various forces. For quantum mechanics, the release of energy occurs in units called quanta .
Quantum gravity is called, in this framework, the field that aims to unify the theory of general relativity and quantum field theory . It should be noted that this quantum field theory manages to describe all fundamental forces with the exception of gravity.
The unification of both types of phenomena would make it possible, for example, to understand what happens inside a black hole and what happened at the beginning of the Big Bang .
Modified gravity is a theoretical scheme that aims to explain physical phenomena without appealing to dark matter.
Circumspection and importance
In another sense, the notion of gravity is related to composure and circumspection . For example: "Solemnly, the government spokesperson gravely announced the death of the prime minister," "I don't like dinners where everyone acts gravely and without spontaneity."
The term also refers to the greatness , importance or enormity of some issue: "The seriousness of the epidemic was evident with the death of twenty people in the metropolitan area of the city," "The police officer was seriously injured after receiving four impacts." bullet in his body .
Types of severity
Regarding relevance, we can differentiate between several types of severity in the field of medicine . In this way, we can establish that the following levels exist:
- Mild . In this case, the symptoms that the patient has cause a minimal alteration in their work or social activity.
- Moderate . The symptoms of the person in question are halfway between mild and severe.
- Grave . The illness or pathology that someone suffers significantly damages the aforementioned activities.
On the other hand, the following conditions are recognized from the variation in symptoms and changes in severity:
- Partial remission . With this concept it is expressed that, of the symptoms that the patient had, only some remain.
- Total remission . All the symptoms of the disorder have now disappeared, but it is still necessary to carry out check-ups to monitor the condition.