Our Unique Planet * With notes provided by David McDonald-Christa McAuliffe Planetarium

1. Our Unique Planet* With notes provided by David McDonald-Christa McAuliffe Planetarium http://www.d21c.com/AAALynx/CB/pl/earth.jpg

2. What is the most unique characteristic of the Earth? • The presence and diversity of LIFE What factors allow this diversity?

3. 1. Star/Solar System Birth Date(Formed from an older solar nebula generation.) • 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) http://www.atomicarchive.com/Fusion/Images/fusion.jpg

4. 2. 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

5. 3. Right Mass/Gravity of the Planet.- Without the right mass/gravity, the atmosphere which surrounds us would move into space as well as us. - 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

6. First – a handy definition: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

7. 4.Right Distance From Parent Star • Water exists in three states of matter • 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 http://ag.arizona.edu/extension/riparian/images/ch3_hydro-cycle.jpg

8. 5. 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. http://www.learner.org/jnorth/images/imageshtml/earth-tilt.gif

9. 6. 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 http://old.grotte-de-han.be/expo/effetserre.jpg

10. 7. 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. Also the moon creates the tides. (High/Low 2 times a day) http://www.esru.strath.ac.uk/EandE/Web_sites/01-02/RE_info/Tidal%20power%20files/image002.jpg

11. 8. 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

12. 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

13. 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 