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PHYSICS
P1- The Earth in the Universe
The Earth

When it was first formed, Earth was completely molten (hot liquid). Scientists estimate Earth is 4500
million years old as it has to be older than its oldest rocks. The oldest rocks found on Earth are
about 4000 million years old.…

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Continental drift

Continental drift theory was produced by Wegener. He saw that the continents had jigsaw fit, with
mountain ranges and rock patterns matching up.

There were also fossils of the same animals on different continents. He said that different continents
had separated and drifted apart. Wegener also claimed that…

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Seafloor spreading

The mantle is fairly solid just below the Earth's crust. Further down it is liquid.

Convection currents in the mantle cause magma to rise. The currents move the solid part of the
mantle and the tectonic plates.

Where the plates are moving apart, magma reaches the surface and…

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The Solar System


The Solar System was formed about 5000 million years ago.

The Solar System started as dust and gas clouds, pulled together by gravity. This created intense
heat. Nuclear fusion began and the Sun (a star) was born. The remaining dust and gas formed smaller
masses which were…

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The Universe

The Universe is much older than the Sun, approximately 14000 million years old.

The Speed of Light

Light travels at very high but finite (limited) speeds. If the distance is great enough, light speed can
be measured.

The speed of light is 300 000km/s (around 1 million times…

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Other Galaxies

If a source of light is moving away from us, the wavelengths of light are longer than if the source is
stationary.

Wavelengths of light from nearby galaxies are longer than scientists expect. This means the galaxies
are moving away from us.

Observations made by Edwin Hubble showed…

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The explanations:

The layer of iridium could be the result of an asteroid collision. A big asteroid would have caused
firestorms, shockwaves and possibly climate change. Dinosaurs couldn't have survived. The collision
could have released sulphur and caused strong acid rain for weeks. Dust could have blocked the Sun
and…

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