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Lecture

EPSC201 Lecture 1 Notes.doc


Department
Earth & Planetary Sciences
Course Code
EPSC 201
Professor
Anthony Williams- Jones

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EPSC201 - Lecture 1 Notes
The universe started with a Big Bang. It
was initially infinite in energy and infinitely
small. Since then, the universe
has been expanding outwards,
and cooling down. It started off
as a slow expansion, and started
to accelerate over time. This is be-
cause as the mass got further away from
other mass, the gravity was less, so it could
travel even faster. As the Universe expands, more
energy is being converted to mass through the equa-
tion E=mc^2 The universe was initially so hot, that there
was no matter. It was all in the form of energy.
We estimate the Big Bang occurred 13.7 billion
years ago. As the universe has expanded, the
distance between stars and galaxies has gradually increased. Things are now
found in clusters throughout the universe. Our star is relatively small, and sits on the arm of the Milky Way
galaxy. We know all the galaxies in the Universe are moving away from each other. How do we know this?
Doppler Effect:
If something is moving away from us, the wavelengths of light will be slightly longer then predicted, so
there is Red shift. We have predicted the wavelength that hydrogen (stars) should emit in the laboratory
on earth. But what we observe, is the galaxies are emitting a slightly redder light towards us. This means
the galaxies are moving away from us. There has been a red shift.
Example – an ambulance is driving toward you, you hear the siren as being slightly higher pitch then if the
ambulance were standing still. As it passes you, the siren now sounds lower in pitch, because it is moving
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