Carl Sagan, from “Cosmos”

Cosmos is a Greek word that means “order”. The ancient Greeks used the word to describe the world and the heavens; they thought both existed together in an orderly way.
Today, we still use the word cosmos to refer to the universe. The universe includes Earth and everything on it; the Sun and all the planets surrounding it; the galaxy that our Sun and many others stars and other objects are part of; and all the galaxies and vast space that exists.

To make an apple pie, you need wheat, apples, a pinch of this and that, and the heat of the oven. The ingredients are made of molecules – sugar, say, or water. The molecules, in turn, are made of atoms – carbon, oxygen, hydrogen and a few others. Where do these atoms come from?
Except for hydrogen, they are all made in stars.
A star is a kind of cosmic kitchen inside which atoms of hydrogen are cooked into heavier atoms. Stars condense from interstellar gas and dust, which are composed mostly of hydrogen.
But the hydrogen was made in the Big Bang, the explosion that began the Cosmos. If you wish to make an apple pie from scratch, you must first invent the universe.

Informazioni su Sabrina Masiero

Ricercatore Astronomo (Tecnologo III livello) presso INAF-Osservatorio Astronomico di Palermo-Gal Hassin, Centro Internazionale delle Scienze Astronomiche di Isnello, Palermo. In precedenza: Borsista presso INAF-Osservatorio Astronomico di Padova e Fundaciòn Galileo Galilei, FGG-Telescopio Nazionale Galileo, La Palma, Isole Canarie.
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