«The universe is a sphere whose center is everywhere and the circumference nowhere. » Pascal Following our perception of the environment through our 5
senses, we describe the space using 3 dimensions.
Is that right or do we have to be more imaginative? Is space closed or infinite?
8.1 Origin
Universe
Still expanding, the universe was born from an infinitely small point of extreme density.
Aged 13,8 billion years, it comprises thousands of billions of galaxies, each containing hundreds of billions of stars.
In 10 billion years, the condensation of particle clouds spawned the galaxies and 3 billion years later, the stars and planets.
The visible universe extends from the infinitely large 100.000
billion of billions of kilometers to the infinitely small: a tenth of a thousandth of a micron.
It is composed of 4% of known matter, 23% of dark matter and 73% of energy. It is therefore mostly made of vacuum and energy.
Black hole
A black hole is a celestial object with an extremely large mass in a very small volume. Its gravitational attraction is such that time stops there and neither matter nor light escape.
Under the effect of this huge attraction, the nearby stars circle in a spiral and finally fall into it.
Black holes began to form with galaxies and have been
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Each galaxy has a black hole in its center.
Earth
From the birth of the Sun, 4,6 billion years ago, dust and gas escape, forming small celestial bodies whose fusion then generated the planets.
After a million years of existence, our solar system has about thirty protoplanets, including the future Earth.
In 10 million years, our planet reached 70% of its size, stabilizing after 100 million.
8.2 Space-time
According to Newton, the space and the time are two
independent notions that can exist separately.
Einstein’s theory of gravitation forces us to revisit these intuitive definitions of the space and time.
The physical space-time entity has four dimensions: three for the space and one for the time.
Durations, distances and gravitation become geometric
properties of the same referential.
A given event is positioned both in time and space by these 4
coordinates.
8.3 Structure
General and special relativity
The principle of relativity was stated indirectly in 1632 by Galileo: all movement is relative.
In his mathematical formulation, he shows that the total relative velocity of the different bodies in motion corresponds to the sum of their respective velocities.
Special relativity.
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In 1905, Albert Einstein brings together the formulas of Henri Poincaré in the theory of special relativity, dealing only with rectilinear and uniform references.
General relativity
The general relativity applies to the reference systems in acceleration leading to the theory of gravitation.
Isaac Newton in 1687 demonstrated that the gravitation was responsible for the fall of bodies and the attraction of stars.
Einstein in 1915 extended it to accelerated movements.
The gravitation is not a force but a spatio-temporal effect close to acceleration, the matter curving the space-time.
Ultimate organization
It is by the power of calculations that theoretical physicists reconcile quantum mechanics and general relativity.
String, loop and parallel universes theory predominate.
They describe the universe as a network, not four-dimensional like our space-time, but about ten dimensions.
String theory
According to the string theory, the matter would consist of one-dimensional filaments, whose vibrations would induce the formation of quantum particles.
These oscillatory movements would extend into 9 parallel dimensions, with the additional tiny dimensions wrapping on themselves.
Loop theory
In the loop theory, the space-time would correspond to an elastic mesh varying with the gravitational field intensity.
It would consist of tangled loops where each crossing
represents an elementary unit.
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In 1950, Hugh Everett assumed the existence of multiple
universes that were perpetually divided.
For Stephen Hawking, the Big Bang simultaneously spawned multiple universes, black holes being open passages between them.
Most parallel universes would be unstable, their fundamental constants being inadequate (mass, gravitation,
electromagnetism...).
8.4 Conclusion
Always expanding, the universe is born from an infinitely small point of extreme density. It is made of vacuum and energy.
The gravitational attraction of a black hole is such that time stops there and neither matter nor light escapes from it.
Each galaxy has a black hole in its center.
Space-time has four dimensions belonging to the same
reference frame: three for the space and one for the time.
Durations, distances and gravitation becoming geometric
properties of the same referential.
At the cosmic level, the space is infinite and would comprise about ten dimensions, most of which being tiny and folded on themselves.
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