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2. The Earth in the Universe
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1.1.2.
The theory of inflation
This modern theory explains what happened during the first moments after the Big
Bang. It studies what occurred one second after the explosion.
Geocentric model
The prefix
geo–
comes from Greek and means ‘earth’. This
model was suggested by
Aristotle
in the 4th century B.C. and
was formalised by
Ptolemy
in the 2nd century A.D. This model
was used until the 16th century. It is based on the following
assertions:
❚
The Earth is spherical and is the centre of the Universe.
❚
The Sun, the Moon and the planets revolve in concentric circles
around the Earth.
❚
The stars are fixed on a dome that also revolves around the
Earth.
Heliocentric model
The prefix
helio–
comes fromGreek and means ‘sun’. This model
was suggested by
Aristarchus of Samos
in the 2nd century
B.C., but it was not until the 16th century that it was proposed
by
Copernicus
and verified by
Galileo.
According to this model:
❚
The Sun does not move and is in the centre of the Universe.
❚
All the planets revolve around the Sun in concentric circles.
❚
The Earth rotates on its axis and the Moon revolves around
the Earth.
❚
The stars are fixed on a dome that does not move.
Create
2.
Find out about the Steady State and the Oscillating Universe theory.
Write a brief description.
Time 0: Big Bang
There was a giant explosion.
Particles were created and a lot
of energy was released.
The first second
After inflation, the universe expanded rapidly. This
expansion caused cooling and created the particles
that compose atoms: electrons, protons and neutrons.
From the 17th century onwards, scientists, like
Johannes Kepler
, discovered that
the stars are not fixed and that the orbits of the planets are elliptical.
1.2.
The position of the Earth in the Universe
Different models have been proposed to explain the Earth’s position in the universe.
The two main models are the geocentric model and the heliocentric model.
