The Sun
•	870,000 miles in diameter (earth? ~8000)
–	Less than one/two billionth of energy made is intercepted by earth; 5 billion years left
–	Energy produced by nuclear fusion
•	nuclear = energy released by reactions involving the nucleus of atoms
•	H  He; 4 million tons each second, 7/10 of 1% given off as heat
–	(H = 1.008; He = 4.003.  4 * 1.008 = 4.032; rest is heat -- E = mc2)
–	Solar constant; average solar radiation rec’d at earth = 1.95 cal/cm2/min
•	Calorie? Amount of heat to raise 1 gm of water 1o C
•	Co = 5/9 (Fo – 32) 
•	Fo = (9/5Co) + 32

All electromagnetic radiation (define radiation? transfer heat w/out physical substance--vacuum) propagate at speed of light (how fast?); wave frequency is inversely proportional to wavelength

•	Energy 
–	Wien’s law
•	Hotter radiating body, shorter the wavelength of max radiation
•	Determine dominant wavelength of object-- at which blackbody radiation reaches its peak
–	m = A/T
•	Where: m = wavelength of max spectral radiance; A = constant; T = temp.
•	Solar max ? = 0.48 T = 6000K; Earth max ? = 9.7  T = 300K

•	Energy
–	Stefan-Boltzmann Law 
•	Hotter objects emit more total energy per unit area than cooler objects
–	M = T4
•	where M= total radiance (W m2),  = Stefan-Boltzmann constant, T = absolute temp of object

–	So, solar radiation hit atmosphere…
•	Reflect
•	Absorb
–	Removes energy from beam of radiation and reradiates it uniformly in all directions at different  (based on absorber’s temp)
•	Scatter
–	Scattering; energy lost by being redirected out of ‘beam’ of radiation, but  doesn’t change

–	So, solar radiation hit atmosphere…
–	Reflect
–	Absorb
•	Removes energy from beam of radiation and reradiates it uniformly in all directions at different  (based on absorber’s temp)
–	Scatter
•	Scattering; energy lost by being redirected out of ‘beam’ of radiation, but  doesn’t change

–	Solar energy hit earth?
•	Absorb - Sun heat earth; earth re-emit as longwave (terrestrial) radiation
•	Reflect – albedo = reflectivity of a substance (snow? 0.95; soil? 0.05)

•	Earth/sun system in balance (100 units in, 100 units out)
–	If not enough? Be like Mars
–	Too much? Burn up like Venus

•	Sun heat Earth; Earth heat atmosphere
–	Only a minute heating of atmosphere by insolation
•	Lag effect = Hi temps ‘lag’ behind hi insolation
–	Why? Insolation outpaces longwave radiation
•	Daily and annually