1. The Big Bang!
ESCI 518
Fall 2004

2. Origins How Do We Know? How and when did the:
universe form?
solar system / Earth form?
Moon form?
What were early Earth conditions?
How Do We Know?

3. Origin of the Universe Big Bang occurred 15 billion years ago
model for the beginning of the universe

4. Building a Universe - infinitely dense point not
governed by our physical laws or
time
- all matter and energy contained
in one point
Einstein’s theory of relativity predicts this “smaller than a proton” time=0 state

5. Building a Universe - instantaneous filling of space with all matter

6. Edwin Hubble Universe is continuously expanding
Galaxy’s velocity is proportional to its distance (galaxies that are twice as far from us move twice as fast)
taken every galaxy the same amount of time to move from a common starting position to its current position

7. Hubble’s Evidence
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.

8. Evidence for Big Bang
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

9. Building a Universe
10-43 s - gravity separates from other forces centimeters
10-35 to 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
years - matter collapses into clouds, making galaxies and stars
Light at 300,000 years
Orion Nebula -

10. When Did the Universe Form?
10 to 20 billion years ago (15)
How do we know?
spreading (Red Shift)
know distances, rates of retreat, relative positions
pervasive background radiation of 2.7°C above absolute zero
afterglow of the Big Bang
Shipp: Red shift - can determine composition of star, and relative movement by measuring its spectrum. Wavelengths shift toward red if moving away. Faster the velocity, more of a red shift.
Wellner: wavelength shifts to the red end of the spectrum as Doppler Effect while light travels through universe (gravitational effect on photons)
Hubble - universe is expanding (red shift) and things farther away are moving away faster (greater red shift)
Differences in age b/c we don’t know the size of the universe.
Doppler effect - shift in wavelength - light and sound
Compressed as it approaches - higher pitched an shorter waved
Stretched as it leaves - lower pitch, longer wave
Orion Nebula -

11. How old is the universe? Speed x time = distance
(distance of a particular galaxy) / (that galaxy’s velocity) = (time) or
4.6 x 10^26 cm / 1 x 10^9 cm/sec = 4.6 x 10^17 sec
~ 15 billion years

12. Features of Our Solar System
in a spiral arm of the Milky Way Galaxy
Sun
9 planets
101 known moons (satellites)
a tremendous number of asteroids
most orbit the Sun between the orbits of Mars and Jupiter
millions of comets and meteorites
interplanetary dust and gases

13. Relative Sizes of the Sun and Planets

14. Solar System Configuration

15. Origin of Our Solar System
Solar nebula theory
cloud of gases and dust
formed a rotating disk
condensed and collapsed due to gravity
forming solar nebula
with an embryonic Sun
surrounded by a rotating cloud

16. Embryonic Sun and Rotating Cloud
planetesimals have formed in the inner solar system
large eddies of gas and dust remain far from the protosun

17. The Planets Terrestrial Planets
Mercury
Venus
Earth
Mars
small, composed of rock, with metal cores
Jovian Planets
Jupiter
Saturn
Uranus
Neptune
large, composed of hydrogen, helium, ammonia, methane, relatively small rocky cores
– Pluto?