13-01-2011, 03:41 PM
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ESCI 518
Fall 2004
Origins
How and when did the:
universe form?
solar system / Earth form?
Moon form?
What were early Earth conditions?
How Do We Know?
Origin of the Universe
Big Bang
occurred 15 billion years ago
model for the beginning of the universe
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
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.
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
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
