Transcript The Big Bang Theory

The Big Bang!
ESCI 518
Fall 2004
Origins
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How and when did the:
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universe form?
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solar system / Earth form?
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Moon form?
What were early Earth conditions?
How Do We Know?
Origin of the Universe
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Big Bang
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occurred 15 billion years ago
model for the beginning of the universe
Building a Universe
- infinitely dense point not
governed by our physical laws or
time
- all matter and energy contained
in one point
http://rainbow.ldeo.columbia.edu/courses/v1001/7.html
Building a Universe
- instantaneous filling of
space with all matter
http://rainbow.ldeo.columbia.edu/courses/v1001/7.html
Edwin Hubble
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Universe is continuously expanding
Galaxy’s velocity is proportional to its distance (galaxies
that are twice as far from us move twice as fast)
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taken every galaxy the same amount of time to move from a
common starting position to its current position
Hubble’s Evidence
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Doppler shifting - wavelength emitted by something moving away
from us is shifted to a lower frequency
Sound of a fire truck siren - pitch of the siren is higher as the fire
truck moves towards you, and lower as it moves away from you
Visible wavelengths emitted by objects moving away from us are
shifted towards the red part of the visible spectrum
The faster they move away from us, the more they are redshifted.
Thus, redshift is a reasonable way to measure the speed of an
object (this, by the way, is the principal by which radar guns
measure the speed of a car or baseball)
When we observe the redshift of galaxies outside our local group,
every galaxy appears to be moving away from us - universe is
expanding.
Evidence for Big Bang
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Red shift - as light from distant galaxies approach earth there is an
increase of space between earth and the galaxy, which leads to
wavelengths being stretched
In 1964, Arno Penzias and Robert Wilson, discovered a noise of
extraterrestrial origin that came from all directions at once radiation left over from the Big Bang
In June 1995, scientists detected primordial helium in the far
reaches of the universe - consistent with an important aspect of the
Big Bang theory that a mixture of hydrogen and helium was created
at the beginning of the universe
Building a
Universe
•10-43 s - gravity separates from other
forces - 10-28 centimeters
•10-35 to 10-32 s - fundamental particles
- quarks and electrons - softball
•10-6 s - quarks combine into protons
and neutrons - solar system
•1 s - electromagnetic and weak nuclear
forces separate
•3 minutes - protons and neutrons
combine into atomic nuclei
•105 years - electrons join nuclei to
make atoms; light is emitted
•105-109 years - matter collapses into
clouds, making galaxies and stars
Orion Nebula - http://stardate.utexas.edu/resources/ssguide/planet_form.html
When Did the Universe Form?
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10 to 20 billion years ago (15)
How do we know?
 spreading (Red Shift)
 know distances, rates of
retreat, relative positions
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pervasive background
radiation of 2.7°C above
absolute zero
afterglow of the Big Bang
Orion Nebula - http://stardate.utexas.edu/resources/ssguide/planet_form.html
How old is the universe?
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Speed x time = distance
(distance of a particular galaxy) / (that galaxy’s velocity)
= (time)
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or
4.6 x 10^26 cm / 1 x 10^9 cm/sec = 4.6 x 10^17 sec
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~ 15 billion years
Features of Our Solar System
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in a spiral arm of the Milky Way Galaxy
Sun
9 planets
101 known moons (satellites)
a tremendous number of asteroids
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most orbit the Sun between the orbits of Mars and
Jupiter
millions of comets and meteorites
interplanetary dust and gases
Relative Sizes of the
Sun and Planets
Solar System Configuration
Origin of Our Solar System
Solar nebula theory
 cloud of gases and dust
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forming solar nebula
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formed a rotating
disk
condensed and
collapsed due to
gravity
with an embryonic Sun
surrounded by a rotating cloud
Embryonic Sun and Rotating Cloud
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planetesimals have formed in the inner solar
system
large eddies of gas and dust remain far
from the protosun
The Planets
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Terrestrial Planets
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Mercury
Venus
Earth
Mars
Jovian Planets
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small, composed
of rock, with
metal cores
– Pluto?
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Jupiter
Saturn
Uranus
Neptune
large, composed
of hydrogen,
helium, ammonia,
methane,
relatively small
rocky cores