1. Conversations with the Earth Tom Burbine tburbine@framingham.edu

2. Energy Energy is the property of a system that enables it to do work

4. Work Work = Force x Distance

5. To do work You need to move something

6. Energy units In English Units, we use calories to measure energy In science (and in this class), we will use joules to measure energy 1 Joule = 1 kg * m 2 /s 2

7. Joule One joule is defined as the amount of work done by a force of one Newton moving an object through a distance of one meter

9. Thermal energy (kind of kinetic energy)‏ Temperature is a measure of the average kinetic energy of the particles Higher temperature – more kinetic energy, particles moving faster For examples, air molecules around you are moving at ~600 m/s http://eo.ucar.edu/webweather/molecules.html

10. Temperature scales In America, we use Fahrenheit Water freezes at 32 degrees F Water boils at 212 degrees F Everywhere else, they use Celsius Water freezes at 0 degrees C Water boils at 100 degrees C

11. In Science Temperature is usually given as Kelvin Zero Kelvin is absolute zero – nothing moves Add 273.15 to the Celsius temperature to get the Kelvin temperature 273.15 Kelvin = 0 degrees Celsius

14. Absolute Zero 0 Kelvin Lowest limit of temperature Molecules have lost all available kinetic energy

15. Power Power = work/time Units of power are watts = Joules/second

16. Flux is the amount of energy (or the number of photons) that passes perpendicularly through a unit surface area per unit time Flux is measured in Joules/(second-meter 2 ) Watts/m 2

17. Blackbody A black body is an object that absorbs all electromagnetic radiation that falls onto it. Perfect emitter of radiation Radiates energy at every wavelength

18. http://www.astro.ncu.edu.tw/contents/faculty/wp_chen/Ast101/blackbody_curves.jpg

19. http://www.rap.ucar.edu/general/asap-2005/Thur-AM2/Williams_DoD_Satellites_files/slide0005_image020.gif

20. Stefan-Boltzman Law Flux = σT 4 Temperature in Kelvin σ = 5.7 x 10 -8 Watt/(m 2  K 4 ) For example, if the temperature of an object is 10,000 K Flux = 5.7 x 10 -8 x (10,000) 4 Flux = 5.7 x 10 -8 x (1 x 10 16 ) Flux = 5.7 x 10 8 W/m 2

21. Wien’s Law Wavelength of Maximum intensity of the blackbody curve peak = 2.898 x 10 -3 m K T (K) T = 10,000 K λ max = (2.898 x 10 -3 /10,000 ) m λ max = 2.0 x 10 -7 meters

23. An Astronomical Unit (AU) is the average distance of the Sun to the Earth

24. Inverse Square Law The solar flux varies inversely by the square of the distance (1/d 2 ) If the Earth was moved to 10 Astronomical Units away, the flux from the Sun would be 1/100 times smaller If the Earth was moved to 100 Astronomical Units away, the flux from the Sun would be 1/10000 times smaller

25. If the Earth was moved to 1 x 10 8 Astronomical Units away, the Sun would be … A) 1 x 10 -12 times dimmer B) 1 x 10 -14 times dimmer C) 1 x 10 -16 times dimmer D) 1 x 10 -18 times dimmer E) 1 x 10 -20 times dimmer

26. If the Earth was moved to 1 x 10 8 Astronomical Units away, the Sun would be … A) 1 x 10 -12 times dimmer B) 1 x 10 -14 times dimmer C) 1 x 10 -16 times dimmer D) 1 x 10 -18 times dimmer E) 1 x 10 -20 times dimmer

29. Solar flux Solar flux at the Earth’s orbit is 1366 W/m 2 If you move the Earth to 2 AU Flux = 1366 W/m 2 (1 AU) 2 (2 AU) 2 Flux = 1366 W/m 2 = 341.5 W/m 2 4

30. http://www.learner.org/resources/series28.html

31. Any Questions?