Philosophy of Science

Science is:
Science is based on the concept that the natural universe behaves in a consistent and predictable pattern

Hypothesis or Theory?

Hypothesis:
Theory:

Scientific Method

The system used to answer questions scientifically - through observations and experimentation

8 Steps
1. Definition of the Problem
2. Literature Search
3. Hypothesis
4. Experimentation and/or Observation
5. Theory
6. Testing of the Theory
7. Publication of Theory
8. Verification by Other Researchers

The Atmosphere

Atmosphere:
Atmos- =
-sphere =

Air:

Studying The Atmosphere

Weather:
Climate:
Meteorology
Meteor- =
-logy =

Earth Systems

A System is:
1) a regularly interacting or independent group of items forming a unified whole.
2) a group of related interacting bodies under the influence of related forces.
Open System:
Closed System:

Geosphere: the solid Earth; earth materials; minerals, rocks, metals (Geology, Geography, Geoscience)
Atmosphere: the gaseous Earth (Meteorology, Climatology)
Hydrosphere: the water Earth (Hydrology, Oceanography)
Biosphere: life on Earth (Biology, Life Sciences)

Composition of the Earth's Atmosphere

Major Components			Minor Components
N2 (nitrogen)	78.084%		Ne (neon)	0.0018%
O2 (oxygen)	20.946%		He (helium)	0.0005%
H2O (water)	0-5%		Kr (krypton)	0.0003%
Ar (argon)	0.934%		CH4 (methane)	0.00017%
CO2 (carbon dioxide)	0.038%		H2 (hydrogen)	0.00006%
			N2O (nitrous oxide)	0.00003%
			Xe (xenon)	0.000009%
			O3 (ozone)	0.000004%
Total Mass	5.136x1026 g		particles (dust and soot)	0.000001%
Total Mass	5.7x1016 tons		CFC (chlorofluorocarbons)	0.00000001%

Origin of the Atmosphere

Linked with the origin of the Earth
The present atmosphere is not the result of accumulation of solar nebula gases
Differentiation formed the atmosphere
More dense material sank toward the Earth's center, while less dense material rose towards the surface.
This less dense material includes gases: out gassing (out gassing occurs at volcanoes)
Original Earth atmosphere:
     1)
     2)
     3)
     4)

What's missing?

From where did the Oxygen come?

Photosynthesis is the process in which the plant takes in CO₂ from the atmosphere plus water and releases O2 as a waste product.
Photosynthesis evolved in blue-green algae approx. 3.5 billion years ago
Small amounts of O₂ into the oceans and atmosphere at this time
At approx. 1.5 billion years ago, organisms evolve that utilize oxygen
1.5 b.y. - 1% atmospheric oxygen present.
550 million years ago - approx. 3% atmospheric oxygen present.
450 million years ago - approx. 10% atmospheric oxygen present.
During the Pennsylvanian Period, 320-286 million years ago, oxygen levels may have exceeded present levels: 23% - 28% atmospheric oxygen
Evidence for high levels of O₂?

Changes in the Composition of the Atmosphere

What are some of the factors which change the amounts of the various components?

Oxygen - O₂
Produced by:
Removed by:

Carbon Dioxide - CO₂
Produced by:
Removed by:

Water - H₂O
Produced by:
Removed by:

Methane - CH₄
Produced by:
Removed by:

Ozone - O₃

Produced naturally in the atmosphere as O₂ + O+ combines to form O₃
Ozone depletion occurs naturally due to: Ultraviolet radiation, nitrous oxide reactions, oxidation reactions, chemical reactions from industrial waste, CFCs

Formation of Ozone:

Destruction of Ozone:

Destruction of Ozone by CFC:

Montreal Protocol on Substance that Deplete the Ozone Layer

Large Scale Structure of the Atmosphere

For the lower portion of the atmosphere, increased elevation means decreased temperature.
Temperature decreases at a constant rate known as the Lapse Rate.
For every 1000 meters of altitude, temperature decreases 6.4°C.

Homosphere:
Heterosphere:

Structure of the Atmosphere

Troposphere
0-12 km (9 to 16 km)
Lower atmosphere - Contains most of the weather that affects us - significant amounts of water - abundant aerosols (fine liquid and solid particles)

Tropopause
approx. 12 km - varies in elevation with seasons and latitude
Level at which temperature stops decreasing and begins increasing

Stratosphere
14 - ~50 km
High altitude air mass - low water and dust content
Ozone layer is found in this layer

Mesosphere
~50 - 80 km
Temperature decreases with higher elevations
Coldest temperatures in the atmosphere

Thermosphere
80+ km
Extremely rarified air
Temperatures increase to more than 1000°C
Due to absorption of shortwave, high energy solar radiation

Ionosphere
60 - 400 km
Electrically charged layer of ionized Nitrogen and Oxygen
Created by shortwave solar radiation
Diurnal variation

Auroras:
Solar radiation and charged particles of the solar wind follow the Earth's magnetic force lines and enter the atmosphere at the poles.

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