The Earth Within The Universe
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Publicado: 25 de octubre de 2011
Unit 1: The Earth within the Universe
1. Theories about the universe
Two of the most influential theories about the universe were:
▪ The geocentric theory: theEarth is at the centre of the universe.
Aristotle (384 – 322 BC) first developed this theory and Claudius Ptolemy (100 – 170 AD) later expanded it.
▪ The heliocentrictheory: the Sun is at the centre of the universe and the Earth revolves around it. Nicolas Copernicus (1473 - 1452) first developed this theory. Galileo Galilei (1564 - 1642)and Johannes Kepler (1571 - 1630) later verified it.
However, today we know that the Earth is a planet that revolves around the Sun, one of the countless stars in ourgalaxy.
▪ Our galaxy is one of many galaxies in the local galaxy clusters.
▪ Our galaxy cluster is one of the countless galaxy clusters in the universe.
The knownuniverse consists of billions or trillions of galaxies: enormous groups of stars and interstellar gas and dust. Galaxies can also contain billions or trillions of stars. Galaxiescontain the following:
▪ Stars. Large spheres of hydrogen and helium which release energy through nuclear fusion. During this process hydrogen particles combine to formhelium particles, which are larger.
Hydrogen particles(helium particles + energy
▪ Nebulae. Very large clouds of dust and gas in outer space.
▪ Star clusters. Relatedstars that are close to each other.
Our galaxy, the Milky Way
Our galaxy, the Milky Way, contains hundred of billions of stars, including the sun. It is composed of anucleus (or central bulge) of old stars, a disk (or spiral arms) of young stars, and a halo of isolated stars and globular clusters. Our Sun is in the Orion Arm of the disk
1. Theories about the universe
Two of the most influential theories about the universe were:
▪ The geocentric theory: theEarth is at the centre of the universe.
Aristotle (384 – 322 BC) first developed this theory and Claudius Ptolemy (100 – 170 AD) later expanded it.
▪ The heliocentrictheory: the Sun is at the centre of the universe and the Earth revolves around it. Nicolas Copernicus (1473 - 1452) first developed this theory. Galileo Galilei (1564 - 1642)and Johannes Kepler (1571 - 1630) later verified it.
However, today we know that the Earth is a planet that revolves around the Sun, one of the countless stars in ourgalaxy.
▪ Our galaxy is one of many galaxies in the local galaxy clusters.
▪ Our galaxy cluster is one of the countless galaxy clusters in the universe.
The knownuniverse consists of billions or trillions of galaxies: enormous groups of stars and interstellar gas and dust. Galaxies can also contain billions or trillions of stars. Galaxiescontain the following:
▪ Stars. Large spheres of hydrogen and helium which release energy through nuclear fusion. During this process hydrogen particles combine to formhelium particles, which are larger.
Hydrogen particles(helium particles + energy
▪ Nebulae. Very large clouds of dust and gas in outer space.
▪ Star clusters. Relatedstars that are close to each other.
Our galaxy, the Milky Way
Our galaxy, the Milky Way, contains hundred of billions of stars, including the sun. It is composed of anucleus (or central bulge) of old stars, a disk (or spiral arms) of young stars, and a halo of isolated stars and globular clusters. Our Sun is in the Orion Arm of the disk
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