The Universe

UNIT I. THE UNIVERSE
1. DEFINITION

The cosmology is the study of the structure and history of the Universe.

The universe is the sum of all that exists, this includes the time, the space, the matter, the energy, etc. According to scientists, the universe has an approximated age of thirteen billion years and a visible extension of ninety-three billion light years.

➢ What´s a lightyear?

➢ What´s a billion?

2. HISTORY OF OUR VISION OF THE UNIVERSE

2.1. FIRST HYPOTHESIS. THE UNIVERSE IS FORMED JUST BY THE MILKY WAY

*The geocentric model
Aristotle (fourth century BC) established that the Earth is motionless and that it is located in the center of the universe. The sun, moon and planets revolve in perfect circles around the Earth. Ptolemy (second century AC)called this model, the geocentric model.

*The heliocentric model
Principio del formulario
Escribe texto o la dirección de un sitio web o traduce un documento.
It was proposed by Copernicus in the sixteenth century. According to this model the sun is motionless, it is located in the center of the universe and the Earth and planets revolve around it.

Galileo Gallilei in 1610 observed with atelescope that Jupiter has four satellites revolving around it. Thus, he concluded that it is not necessary that all bodies revolve around the Earth.

2.2.The discovery of the Andromeda galaxy
Hubble and his collaborators found this galaxy in 1917 using the great Hooker Telescope in California. Thanks to this discovery, it was proved that the universe was larger than it was thought. It wasn´tformed just by our galaxy, but it was much more extensive and consisted of millions of galaxies like ours.
Escuchar
Leer fonéticamente

2.3. THE BIG BANG THEORY
In 1929 Hubble discovered that the galaxies move away from each other at speeds proportional to their distance. This is called “Hubble´s Law”.
The expansion not only affects to the matter ;to the galaxies that are farther apart. Italso affects to the radiation. When traveling in a universe that is becoming larger, the wavelength increases. So the light is increasingly red. This phenomenon is called redshift. Thanks to this phenomenon Hubble realized that galaxies are moving away.
Therefore, the universe is dynamic, it is an universe in expansion. As a result, the universe is getting bigger. Which means that in the pastit was smaller and compacted. So the universe began as an explosion, which resulted in the current expansion of the universe. The model was named by Fred Hoyle.

What happened after the Big Bang?

The universe was very hot, it was formed by a plasma (similar to a gas) of protons and electrons particles. Light interacted with this plasma. Nuclear reactions were produced and atomic nuclei wereformed. These atomic nuclei consisted of several protons and neutrons, such as helium, lithium, etc. This phenomenon is called primary nucleosynthesis.

Subsequently, the universe was cooling down and nucleosynthesis ended. The proportion of universe gases was similar to the current proportion: 25% helium and 74% hydrogen atoms (the rest of gases were synthesized by the stars).

As the atomicnuclei were formed light didn´t interact with them, so the gases were transparent. The expansion continued and the atoms were grouped and they formed higher density structures. These structures are the galaxies which contain stars and planets.

[pic] [pic]

➢ Define atom and its components

3. THE FUTURE OF THE UNIVERSE (en el libro en español)

4. BIG STRUCTURES OF THEUNIVERSE

4.1. CUMULUS AND GALAXIES

Galaxies are huge groups of stars, gas and dust. They differ by their different shapes and sizes, and the number of stars that they contain. There are different types:

-Spiral galaxies. Contain a central area or core and a variable number of arms.

-Elliptical galaxies. They haven´t arms. They consist of old stars and are the largest galaxies known....