GHY 104 1st Edition Lecture 4Annual March of the Seasons- Winter Solstice- December 21 or 22- Subsolar point = Tropic of Capricorn- Spring Equinox- March 20 or 21- Subsolar point = Tropic of Cancer- Fall Equinox- September 22 or 23 - Subsolar point = EquatorOne more point Re: rotation- Moon and Earth rotate Counter Clockwise- Every point on Earth takes same 24 hour to complete rotation- However, linear velocity varies with latitude - Equator: 25 k long. Rotational velocity at equator: 1000 mph- The 60th parallel is one half length of equator, so rotational velocity is only 520 mph- At the poles, the velocity is 0⁰Sun Angle and Subsolar Point- The subsolar point can only range between 23.5⁰ N and 23.5⁰ S. During the equinoxes, the subsolar point is located directly on the equator.- The Sun therefore “travels” 47⁰ north to south between 23.5⁰ N and 23.5⁰ S during a complete year.- Seasonal Observations at 40th parallel NImportant Latitudes- North Pole = 90⁰ N- Artic Circle = 66 ½ ⁰ N- Trophic of Cancer = 23 ½ ⁰ NThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Equator = 0⁰- Trophic of Capricorn = 23 ½ ⁰ S- Antarctic Circle = 66 ½ ⁰ S- South Pole = 90⁰ SChapter 3: Earth’s Modern AtmosphereEarth’s Modern Atmosphere- Atmospheric Profile- Composition- Temperature- Functions- We all affect the atmosphere (ozone, acid deposition)- Thin envelope- Series of concentric spheres that grade into one another - Bound to the planet by gravity- Gravity causes air molecules to create air pressure (force/unit area)- We create pressure inside of us- Atmosphere exerts – 14.7 lb/in2 at sea level- Air: more dense near surface, thins rapidly with increasing altitude - 75% atmosphere mass compressed below 36k fAtmospheric Composition- Heterosphere- outer atmosphere- 80 km (50 mi) outwards to top of thermosphere- Layers of gases sorted by gravity (not evenly mixed)- >0.001% of atmosphere’s mass- Homosphere- inner atmosphere- Surface to 80 km - Gases evenly blended- Present proportion evolved – 500 mya- Top of heterosphere is at 480 km – top of the principle atmosphere- Beyond that. . . Exosphere- Contains scarce, lightweight H and He atoms weakly bound as for 20 k mi from