Transcript aaaa - Londonderry School District

Our Unique Planet
* With notes provided by David McDonald-Christa McAuliffe Planetarium
http://www.d21c.com/AAALynx/CB/pl/earth.jpg
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What is the most unique
characteristic of the Earth?
• The presence and diversity of life
What factors allow this diversity?
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I. Star/ Solar System
Characteristics
http://www.mallorcaweb.net/masm/Planetas/nuevosplanetas.jpg
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a. Star/Solar System Birth Date
• Very long ago planets would not contain
enough heavy elements.
• We need to have elements past the first
generation star level for living things.
(need supernova for fusion of elements
heavier than iron)
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http://www.atomicarchive.com/Fusion/Images/fusion.jpg
b. Age of our Sun
• The Sun needs to be in a stable burning
phase (main sequence) for constant
radiation and luminosity (heat and energy
source).
http://helios.augustana.edu/~lc/sunxray.gif
http://www.highwaygirl.com/hwg/images/star.jpg
http://www.pd.astro.it/education/PlanetV/planetarium/icons/EQUI.GIF
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II.
Earth Characteristics
http://www.d21c.com/AAALynx/CB/pl/earth.jpg
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a. The Earth lies within the
habitable zone of the Sun.
Habitable Zone (HZ):
The distance from the star where the average
temperature of the planet allows liquid water to exist.
http
://www.mallorcaweb.net/masm/Planetas/nuevosplanetas.jpg
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Right Distance From Parent Star
•
•
•
•
Too great= too cool for stable water cycle
Too close= too hot for stable water cycle
This is the main aspect of Habitable Zone
Also, most life needs 0-100 Degrees Celsius
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http://ag.arizona.edu/extension/riparian/images/ch3_hydro-cycle.jpg
b. Right Mass/Gravity of the Planet.
- Without the right mass/gravity, the atmosphere which
surrounds us would move into space as well as us or
we wouldn’t be able to breathe.
- This also allowed the Iron Catastrophe to occur
which allowed the earths’ inner layers to form.
http://static.howstuffworks.com/gif/hot-air-balloon-atmosphere.jpg
http://teachertech.rice.edu/Participants/louviere/Images/profile.gif
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c. Right Carbon Dioxide and Water
Vapor Levels in the Atmosphere
• If greater amounts= runaway greenhouse effect
(warming of the earth).
• If lesser amounts= insufficient greenhouse
effect (cooling of the earth).
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http://www.n-ergise.net/cnt/txt/40/1/greenhouse_effect.gif
d. Right Ozone Level in
Atmosphere
• If greater amounts of ozone= surface
temperatures too low.
• If less amounts of ozone= surface
temperatures too high and too much UV
radiation at surface.
http://www.epcc.pref.osaka.jp/apec/eng/earth/ozone_layer_depletion/image/zu_g01.gif
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e. Right Thickness of Crust
• If Thicker= More oxygen in crust.
• If Thinner= More volcanic and tectonic
plate activity.
http://geography.sierra.cc.ca.us/Booth/Physical/chp13_earth/crust_composition.gif
http://www.pacificislandtravel.com/nature_gallery/volcanoes2.gif
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Seismic Activity
• Greater= destruction of life forms
• Less= nutrients on ocean floors (from river
runoff) would not be recycled by tectonic
uplift.
http://rst.gsfc.nasa.gov/Sect2/platespread.jpg
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f. Right Internal Earth Layers – Convection
currents in the outer core produce the
“Magnetic Field” surrounding the earth.
This provides protection from hard stellar
radiation (ex. Solar Wind ) for us as well
as keeping the atmosphere from being
swept away.
http://www.instituteforinquiry.org/inquiries/graphics/electrostorm.jpg
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g. Right Rotation Period
• If days (rotation period) were longer the diurnal
temperature differences would be too great (temperature
between night and day).
• If days were shorter, atmospheric wind speed would be
too great. (due to pressure differences caused by
different temperature air masses)
http://www.physicalgeography.net/fundamentals/images/heatingwind.GIF
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http://old.grotte-de-han.be/expo/effetserre.jpg
h. Right Gravitational Interaction
with the Moon
Affects climate and weather patterns due to
influencing the earth’s spin as well as reduces
the wobbling motion of the Earth.
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http://www.esru.strath.ac.uk/EandE/Web_sites/01-02/RE_info/Tidal%20power%20files/image002.jpg
i. Right Axial Tilt
• If too much greater - the surface temperature
differences would be too great. Ice and water vapor
would travel to the poles, no water anywhere else.
• If much less - the habitable zone would shrink in size
(think narrow band around equator)
• The tilt also allows the seasons to occur.
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http://www.learner.org/jnorth/images/imageshtml/earth-tilt.gif
Think About This……
• In 1999 Hubble space telescope indicated 125 billion
galaxies.
• Times that by a factor of 8 =1 trillion (1012) galaxies
• There are approximately 100 billion stars per galaxy
(1011)
• (1011) stars x (1012) galaxies = 1023 stars in the universe
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Probability
• If we consider (on average) a 1% chance of
each of the previously mentioned factors
occurring favorable to life, that is….
• One chance in 1040
• Compared to “only” 1022 stars in the Universe
• Therefore… we have a pretty unique home 
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