Download Chpt17-18

Chapters 17,18: Cosmology and Life in the Universe
Nearly every speck of light in
the image is a galaxy.
Chapters 17,18: Cosmology and Life in the Universe
A map of the
distribution of galaxies
seen out of the plane of
the Milky Way
Chapters 17,18: Cosmology and Life in the Universe
Is the universe infinite or
closed. Olbers’s Paradox says
in must be finite because if it
was infinite then every
direction one looked in space
would ultimately land on the
surface of a star and the whole
sky would be as bright as the
Sun’s surface.
Chapters 17,18: Cosmology and Life in the Universe
Hubble’s Law states that
Recession velocity = Ho X distance
Where Ho is the Hubble constant
Since velocity is distance/time, if we assume the universe has
been expanding since the Big Bang then we can invert the
equation for Hubble’s law and calculate how long it has been
since the Big Bang.
Time since Big Bang = 1/Ho gives 14 billion years
Chapters 17,18: Cosmology and Life in the Universe
At a time 1/Ho the universe began in an event we call the Big Bang
But like living on the surface of a balloon, we can see no beginning.
Chapters 17,18: Cosmology and Life in the Universe
Also, as the balloon expands we see all parts reseeding from all
others. This explains why we see all the other galaxies speeding
away from us.
Chapters 17,18: Cosmology and Life in the Universe
The expanding universe also caused the wavelengths of radiation
from the Big Bang to be red shifted. We see this today as the
microwave background radiation.
Chapters 17,18: Cosmology and Life in the Universe
Classical thought says depending on
how much matter there is in the
universe we have three possible
outcomes.
Modern evidence points to a
fourth outcome, an accelerating
expansion.
Chapters 17,18: Cosmology and Life in the Universe
1) too little mass means we expand
forever (death by ice)
2) too much mass and we get the
big crunch (death by fire)
3) just the right amount and we
eventually stop expanding (also
death by ice)
4) But truth is an increasingly
expanding Universe. How can
this be?
Chapters 17,18: Cosmology and Life in the Universe
Currently astronomers cannot find enough mass to close the
Universe.
The increasingly expanding Universe suggests we have
negative energy and/or anti-gravity. This is a very active area
of research.
Chapters 17,18: Cosmology and Life in the Universe
As the Big Bang occurred we went from
a radiation dominated universe to a
matter dominated universe
Chapters 17,18: Cosmology and Life in the Universe
Hydrogen and Helium are the only
two atoms made during the Big
Bang. All other elements were
manufactured in by the stars and
supernovae explosions.
The ration of Helium to Hydrogen
is an important constraint to current
theories.
It is difficult to tell if spacetime is
curved because the distances mw
can measure are so small compared
to the universe
Chapters 17,18: Cosmology and Life in the Universe
Somehow dark mater
caused the ordinary mater in
the Universe to be clumpy.
Chapters 17,18: Cosmology and Life in the Universe
Is there anybody out there?
Chapters 17,18: Cosmology and Life in the Universe
Chapters 17,18: Cosmology and Life in the Universe
While we can recreate amino acids under
early Earth conditions, we have not been
able to “create” Life.
Radio astronomers can detect
complicated molecules in dark molecular
clouds.
Miller-Urey experiment
Chapters 17,18: Cosmology and Life in the Universe
Organic mater is found in
meteorites.
And life is found to grow
where we never thought it
could exist.
Chapters 17,18: Cosmology and Life in the Universe
Different star have different ranges of habitable zones
Chapters 17,18: Cosmology and Life in the Universe
Drake’s Equation
number of
technological,
intelligent
civilizations
now present
in the Galaxy
fraction of those
X habitable planets
on which life
arises
X
rate of star
formation,
= averaged over
the lifetime
of the Galaxy
fraction of
stars
X having
planetary
systems
fraction of those
life-bearing planets
on which intelligence
evolves
fraction of those
intelligent-life
X planets that
develop techbiological society
average number
of habitable
X
planets
within those
planetary systems
X
average lifetime of
a technologically
competent
civilization.
Chapters 17,18: Cosmology and Life in the Universe
Many astronomers think the best place
to look for ET is in the water hole part
of the electromagnetic spectrum.