Download Unit 1

EXAMS:
Group Lec 002 May 15, 2:45-4:45pm Van Vleck B102
Group Lec 001 May 16, 12:25-2:25pm Camberlin 2103
A Timeline of the Universe
The Origin of Helium
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Immediately after the Big
Bang, only protons and
electrons existed
Shortly after the BB,
temperature and density was
high enough for deuterium to
form by fusion
After 100 seconds or so,
temperature cooled enough so
that deuterium could fuse into
helium nuclei
The temperature continued to
cool, and fusion stopped after a
few minutes.
Big Bang theory predicts that
around 24% of the matter in the
early universe was helium,
which matches what we see.
The Epoch of Inflation
• Modern technology allows
us to test theories back to a
time 10-33 seconds after the
Universe Birth (UB).
• Physics as we know it
ceases to function at 10-43
seconds after the UB, called
the Plank Time
• Using particle colliders,
scientists have uncovered a
number of clues about what
happened in the early
universe, after the Plank
time
• The early universe
underwent a period of very
rapid expansion
• By 10-33 seconds, the universe expanded from
the size of a proton to the size of a basketball
• This expansion is called inflation
Expansion Forever? Or Collapse?
• The fate of the universe is ultimately
controlled by its total amount of
energy
– Energy of expansion (positive)
– Gravitational energy that can slow the
expansion (negative)
– Binding energy
• If the total energy is positive or
zero, the expansion continues
forever
• If the total energy is negative, the
expansion will halt, and the
universe will contract and
eventually collapse.
Dark Energy
• Dark energy may provide the solution
to the mystery
• Dark energy remains constant
everywhere, regardless of the
universe’s expansion
• Provides an outward push to accelerate
expansion
• Dark energy must make up
around 70% of all of the
energy in the universe
• Much work remains to be
done on this frontier…
Life on Earth
• Life formed on Earth
relatively soon after the
planet’s formation
– For ¾ of the Earth’s history,
only algae and single-celled
life forms existed
– Slowly, more complex
lifeforms developed
• By 250 million years before the
present, dinosaurs and early
mammals had evolved.
• Hominids, our distant ancestors,
developed 5.5 million years ago
• Homo Sapiens evolved only
500,000 years ago!
Figure 83.04
• Life tends to draw on the substances that
are most plentiful: Carbon, Nitrogen,
Oxygen and Hydrogen
• Amino acids are organic molecules
containing these substances
• Amino acids form proteins, which provide
structure and energy to cells
• All life contains DNA – this instruction
packet contains all the information needed
to build an organism
The Origin of Life
• So how did amino acids form out
of the substances available on the
early Earth?
• Probably started thanks to complex
chemical reactions in the
atmosphere and surfaces of Earth
• The Miller-Urey experiment
attempted to duplicate the
environment of the early Earth
• A variety of complex organic
molecules formed in their
“atmosphere”
Fossil Eukaryote Algae
The Search for Life on Mars
• It appears that Mars at
some point in its history
was very much wetter
and warmer than it is
today
• Scientists have been
looking for life there
• The Viking landers
(1970’s) tested for the
presence of microbes,
but returned
inconclusive results
• We are still looking!
Fossils of Ancient Martian Life?
SETI
• SETI: Search for Extra-Terrestrial
Intelligence
• Listens for electromagnetic evidence of
intelligence elsewhere in the universe
• To date, evidence has been sparse.