# The laws of the Universe

No one has imposed them, but the Universe seems to be governed by rules or laws that scientists have tried to discover throughout history. And in that they continue.

Here are some of the fundamental laws that govern our Universe:

## Kepler's Laws

These are three laws about the movements of the planets formulated by the German astronomer Johannes Kepler in the early seventeenth century.

Kepler based his laws on planetary data gathered by Danish astronomer Tycho Brahe, of whom he was an assistant. His proposals broke with the old belief, held for centuries, that the planets of the Solar System moved in circular orbits.

First law: The planets revolve around the Sun in elliptical orbits in which the Sun occupies one of the foci of the ellipse.

Second Law: The areas swept by the segment that joins the Sun with the planet (vector radius) are proportional to the times used to describe them. As a consequence of this law, the closer the planet of the Sun is, the faster it moves.

Third law: The squares of the sidereal periods of revolution of the planets around the Sun are proportional to the cubes of the semi-major axes of their elliptical orbits. This allows us to deduce that the planets farthest from the Sun orbit at a slower speed than the nearby ones; It says that the period of revolution depends on the distance to the sun.

These laws of Kepler played an important role in the work of the 17th-century English astronomer, mathematician and physicist Isaac Newton, and are fundamental, for example, in understanding the orbital trajectories of the Moon and artificial satellites.

## Law of universal gravitation

Gravitation is the property of mutual attraction that all objects composed of matter possess. It is sometimes used as the term "gravity", although this refers only to the gravitational force exerted by the Earth

Gravitation is one of the four basic forces that control the interactions of matter. So far they have not had attempts to detect gravitational waves that, as the theory of relativity suggests, could be observed when the gravitational field of an object of great mass is disturbed.

The law of Universal Gravitation, formulated by Isaac Newton in 1684, states that the force of gravitational attraction between two bodies is directly proportional to the product their masses and inversely proportional to the square of the distance between them.

## The Doppler Effect

The variation of the wavelength of light, electromagnetic radiation and sound of the bodies informs about their movement.

When a vehicle approaches we hear its engine sharper than when it moves away. Similarly, when a star or a galaxy approaches, its spectrum shifts towards blue and, if they move away, towards red.

At the moment, all observed galaxies move towards red, that is, they move away from here.

Discover more:
• Laws and Theories of Physics and Astronomy

 ◄ Previous Measures of the Universe