Origins

• ORIGIN OF THE UNIVERSE

• OBSERVATION

– Universe is Expanding

– suggested by the “Red Shift” (Hubble, 1927)

– Red shift can be explained by the Doppler Effect

ORIGIN OF THE UNIVERSE

• EXPLANATION

– “ The Big Bang” => 14-20 billion years ago the universe began during a cataclysmic release of energy from a point source of infinite mass.

• SEQUENCE OF EVENTS

– quark soup - inflation

– 300k - photons released - H & He

– Continued expansion

– 1 bill. Years - first galaxies form

• What Happens Next?

Origin of the Solar System

• OBSERVATIONS

– Elliptical orbits in the same plane

– Planets rotate in the same direction as they revolve around sun

– Titus-Bode Rule

– 99% of mass in sun 99% of angular momentum in the outer planets

– Terrestrial versus Jovian planets

– discs of dust around young stars

Origin of the Solar System

• EXPLANATION

– Nebular Hypothesis (Chemical Condensation Sequence)

– ~5 bill. yrs. ago - solar system began as large, slowly rotating cloud of dust and gas - Solar Nebula

=> material from a supernova

Nebular Hypothesis

• Cooling and Gravity => from cloud to sphere.

• Velocity of rotation increases => sphere to disk.

• Most of mass near center of disk => proto-sun.

• Sun turns on - H + H = He -> nuclear fusion

• Planets form by chemical condensation/accretion.

The Early Earth

• Origin=> 4.6 b.y. ago => condensation/accretion

• Earth heats up

• Density Differentiation

• A layered earth - core, mantle, crust

The Early Earth

Origin of the Atmosphere & Oceans

=> the early Atmosphere

– Outgassing => “The Big Burp”

– H, H₂O (vapor), CH₄, NH₃

• source of liquid H₂O

– Condensation

– Comets

– volcanoes

=> the early Oceans

The Age of the Earth

• How do we know that the earth is 4.6 billion years old

• Radiometric Dating

– Parent-daughter pairs

– 1/2 life

– Oldest rocks ~4 bill. yrs.

– Meteorites - 4.5 bill. yrs.

Geologic Time Scale

• Graphic depiction of Earth history

• Units of Time

• Eon, era, period, epoch

• Based on the first appearance of certain types of organisms

• Calibrated with radiometric dating

Water on Earth

• 2/3rds of the earth’s surface covered with water

• 3 major oceans

– Pacific, Atlantic, and Indian

• Liquid water on earth =fortuitous

– Distance from the sun

The Hydrologic Cycle

• The solar powered cycling of water on Earth

• PROCESSES

• Evapotranspiration - condensation - precipitation

The Hydrologic Cycle

• Precipitation on land

– Runoff & infiltration

– Storage

The Hydrologic Cycle

• The major reservoir = the oceans

• Other reservoirs

– Ice caps & glaciers

– Groundwater

– Lakes

– Soil moisture

– Atmosphere

– Rivers

– Balance

– Residence time

Land versus Water

• Hypsographic Curve

– Elevation versus surface coverage

– 29% above sea level, 71% below - changes through time