Conversations with the Earth Tom Burbine tburbine@framingham

1. Conversations with the EarthTom Burbinetburbine@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*m2/s2

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-meter2) Watts/m2

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

20. Stefan-Boltzman Law • Flux = σT4 • Temperature in Kelvin • σ = 5.7 x 10-8 Watt/(m2K4) • 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 1016) • Flux = 5.7 x 108 W/m2

21. Wien’s Law • Wavelength of Maximum intensity of the blackbody curve peak = 2.898 x 10-3m • K T (K) • T = 10,000 K • λmax = (2.898 x 10-3/10,000 ) m • λmax = 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/d2) • 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 108 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 108 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/m2 • If you move the Earth to 2 AU • Flux = 1366 W/m2 (1 AU)2 (2 AU)2 • Flux = 1366 W/m2 = 341.5 W/m2 4

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

31. Any Questions?