Charles Hakes Fort Lewis College1

Charles Hakes Fort Lewis College2 Black Bodies/ Atmospheres/

Charles Hakes Fort Lewis College3 Outline Remove “checked” items from folder. Review Interiors/Magnetospheres Kinetic Energy/Temperature Atmospheres

Charles Hakes Fort Lewis College4 Logistics Test 2 - Week from Wednesday Review Blackbodies Atmospheres Green House Effect

Charles Hakes Fort Lewis College5 Lab Notes Any outside “extra” lab(s) due this week if you want credit before mid-term! You need 40 lab points by mid-term to get full (100%) lab credit. (This is not an issue for most of you.) Start outside labs! Spectroscopy in-class lab next week. (?)

Charles Hakes Fort Lewis College6 Which is colder? A) 100° C B) 200° F C) 300° K

Charles Hakes Fort Lewis College7 Temperature Temperature is just a measure of the average kinetic energy of a body’s molecules.

Charles Hakes Fort Lewis College8 Tornado

Charles Hakes Fort Lewis College9 Tornado Tornado photo courtesy of Gary Gianniny and from Scott White.

Charles Hakes Fort Lewis College10 Which temperature will freeze water? A) 65° F B) 5° C C) 263 K

Charles Hakes Fort Lewis College11 Temperature Temperature is just a measure of the average kinetic energy of a body’s molecules. Go to Solar System Collaboratory to see temperature scales.Solar System Collaboratory

Charles Hakes Fort Lewis College12 More Precisely 2-1 The Kelvin Temperature Scale

Charles Hakes Fort Lewis College13 Temperature With enough kinetic energy (temperature), molecules can “escape” from a planet.

Charles Hakes Fort Lewis College14 Small Group Exercise Normal Human body temperature is 37 ° C. What is this temperature in Kelvins?

Charles Hakes Fort Lewis College15 Heat Transfer Conduction Transfer from one mass to another mass that is touching. Convection Transfer though a gas (air) that moves across a mass Radiation Transfer using electromagnetic radiation This is the least efficient method This is the only method available in/through space

Charles Hakes Fort Lewis College16 Albedo Albedo - the fraction of light that is reflected from a planet (or other solar system body). A unitless number from 0 to all light is absorbed (very black) 1 - all light is reflected (very white) Earth's average albedo is 0.30, so 30% of the sunlight is reflected. The light absorbed would be one minus the albedo. For the Earth, =0.70, so 70% of the light is absorbed.

Charles Hakes Fort Lewis College17 Blackbody Radiation “Blackbodies” are not black. Blackbody Radiation is from an “ideal” object with albedo = 0. Any dense, warm, object can be approximated as a “blackbody”. The “peak” of the radiation “curve” is related to the temperature of the radiator.

Charles Hakes Fort Lewis College18 Figure 2.9 Ideal Blackbody Curve

Charles Hakes Fort Lewis College19 Radiation Higher temperature bodies radiate energy in shorter wavelength radiation. The Sun radiates at visible wavelengths The Earth (and other planets) radiate at much longer wavelengths. Go to Solar System Collaboratory to see black body page.Solar System Collaboratory

Charles Hakes Fort Lewis College20 Figure 2.10 Blackbody Curves Note the logarithmic temperature scale. For linear scale, go look at the “black body” section of: do.edu/ do.edu/ example - oven

Charles Hakes Fort Lewis College21 Wein ’ s Law The “peak” frequency of the radiation “curve” is directly proportional to the temperature of the radiator.

Charles Hakes Fort Lewis College22 Small Group Exercise Normal Human body temperature is 37 ° C. What is this temperature in Kelvins? What is the peak wavelength emitted by a person at this temperature?

Charles Hakes Fort Lewis College23 Figure 2.8 Electromagnetic Spectrum

Charles Hakes Fort Lewis College24 What is the peak wavelength emitted by an object with temperature 6,000 K? A) 4.8x10 -5 cm B) 4.8x10 -4 cm C) 2.9x10 -5 cm D) 2.9x10 -4 cm

Charles Hakes Fort Lewis College25 Planet Temperature Go to Solar System Collaboratory on EVM “physics” page.Solar System Collaboratory A planet must balance absorbed light and radiated light to get a temperature. Light intensity decreases with distance. (another 1 /r 2 law) Farther from the sun, the absorbed light is less.

Charles Hakes Fort Lewis College26 Planet Temperature Go to Solar System Collaboratory on EVM “physics” page.Solar System Collaboratory A planet must balance absorbed light and radiated light to get a temperature. Light intensity decreases with distance. (another 1 /r 2 law) Farther from the sun, the absorbed light is less. Go to Solar System Collaboratory on planet temperature page.Solar System Collaboratory

Charles Hakes Fort Lewis College27 Figure 5.7 About 30% of the sunlight hitting the Earth is reflected

Charles Hakes Fort Lewis College28 To Atmosphere or Not Once you know a planet’s temperature you can see if it will have an atmosphere, and how that atmosphere can affect a planet’s temperature. Compare kinetic energy of molecules with “escape velocity” from the planet. Light molecules (of a given temperature T) move faster than heavy molecules of the same temperature. A small fraction will always escape.

Charles Hakes Fort Lewis College29 To Atmosphere or Not Primary atmosphere What a planet had after formation Mostly H, He - almost all gone from the terrestrial planets (never really was here) Secondary atmosphere Heavier molecules N 2, CO 2 From rock outgassing H 2 O from outgassing and comet impacts. O 2 from Life

Charles Hakes Fort Lewis College30 Earth’s Atmosphere 78% nitrogen 21% oxygen - this is from living organisms Plus Ar, CO 2, H 2 O. Note layers

Charles Hakes Fort Lewis College31 Figure 5.5 Earth ’ s Atmosphere

Charles Hakes Fort Lewis College32 Meteorology Science dealing with phenomena in the atmosphere (Not the study of meteors) Warm air rises and expands Cold air sinks and shrinks Must conserve linear and angular momentum.

Charles Hakes Fort Lewis College33 Figure 5.6 Convection

Charles Hakes Fort Lewis College34 Removing all greenhouse gasses from the Earth’s atmosphere would be good A) True B) False

Charles Hakes Fort Lewis College35 Three Minute Paper Write 1-3 sentences. What was the most important thing you learned today? What questions do you still have about today’s topics?