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Temperature of the Earth

General Physics 1

Presentation 1 group 2

24 Jan 2009

trimester 2, 2008-2009

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- 1. THE TEMPERATURE OF THE EARTH
- 2. Introduction <ul><li>How hot is the earth? </li></ul><ul><li>There are several ways </li></ul><ul><li>to look for an answer </li></ul><ul><li>to this. One way is to look </li></ul><ul><li>at ways in which </li></ul><ul><li>the earth </li></ul><ul><li>receive energy. </li></ul>
- 3. How to measure the temperature? <ul><li>According to IPAC </li></ul><ul><li>Kelvin temperatures </li></ul><ul><li>A Kelvin temperature is given as, for instance, 292 K . </li></ul><ul><li>Zero is absolute zero . </li></ul><ul><li>Nitrogen boils at 77 K. </li></ul><ul><li>The freezing point of water is 273 K . </li></ul><ul><li>A nice warm day is 300 K. </li></ul><ul><li>Water boils at 373 K . </li></ul><ul><li>The temperature of the surface of the sun is about 6000K. </li></ul>
- 4. How thermal energy is transferred <ul><li>Conduction </li></ul><ul><li>Radiation </li></ul><ul><li>Convection </li></ul>
- 5. Solar irradiance describes the radiant energy emitted by the sun over all wavelengths that falls each second on 1 square meter outside the earth's atmosphere. Solar irradiance
- 6. Conduction <ul><li>Conduction is the transfer of energy through matter from particle to particle. It is the transfer and distribution of heat energy from atom to atom within a substance. </li></ul>
- 7. Conduction and the Earth <ul><li>Energy from the Sun travels in the form of Ultra Violet and visible radiations through a process called radiation. Then as it reaches the it get absorbed to the Earth surface through conduction process. </li></ul>
- 8. Radiation
- 9. Radiation <ul><li>A process in which energy emitted by one body </li></ul><ul><li>Travels through a medium or through space, ultimately to be absorbed by another body. </li></ul><ul><li>There are many types of radiation ionizing radiation, particle radiation, electromagnetic radiation, non-ionizing radiation, thermal radiation etc. </li></ul>
- 10. How it effects the earth?
- 11. What happens ?? <ul><li>The Sun is the source of all radiation and energy coming to the Earth from space . </li></ul><ul><li>The Earth's surface doesn't take up all the sunlight, but sends a certain part of it directly back into space . </li></ul><ul><li>Absorption of sunlight doesn ’ t only take place at the surface. Gas molecules and particles in the air also absorb sunlight. </li></ul><ul><li>The sunlight which reaches the Earth, warms its surface. The Earth sends this warmth back into space as infra-red heat radiation . </li></ul>
- 12. <ul><li>Convection is heat transfer by mass motion of fluid such as air or water. </li></ul><ul><li>When hot air expand, It become s less dense , and rises </li></ul>Heat Convection
- 13. <ul><li>Convection can also lead to circulation in a liquid, as in the heating of a pot of water over a flame. </li></ul><ul><li>Heated water expands and becomes more buoyant . Cooler, more dense water near the surface descends and patterns of circulation can be formed </li></ul>
- 14. <ul><li>Convection is thought to play a major role in transporting energy from the center of the Sun to the surface, and in movements of the hot magma beneath the surface of the earth. </li></ul><ul><li>The visible surface of the Sun ( the photosphere ) has a granular appearance with a typical dimension of a granule being 1000 kilometers . </li></ul><ul><li>The granules are described as convection cells which transport heat from the interior of the Sun to the surface . </li></ul>From the NASA Solar physics website credited to G . Scharmer and the Swedish Vacuum Solar Telescope
- 15. How much does the earth receive energy ? <ul><li>Earth receives one part in 2.2 billion of the radiation emitted by the sun. Here's how to calculate this. Let r = radius of earth = 4000 miles R = earth-sun distance = 93,000,000 miles area of sun-centered sphere at earth's location = 4пr^2 cross-section of earth for absorbing radiation = пr^2 ratio = 4*(R/r)^2 = 2.2 billion So the amount of sunlight that reaches the earth is 0.00000005% of the sun's total luminosity. Once the sunlight reaches the earth, some is reflected by the atmosphere and some is absorbed by the atmosphere. According to Christa McAuliffe Planetarium, 9% is reflected by the atmosphere and 22% is absorbed by the atmosphere. </li></ul><ul><li>According to naturetech, " Earth receives 174 petawatts of incoming solar radiation ( insolation ) at the upper atmosphere at any given time . When it meets the atmosphere, 6 percent of the insolation is reflected and 16 percent is absorbed . Average atmospheric conditions ( clouds, dust, pollutants ) further reduce insolation traveling through the atmosphere by 20 percent due to reflection and 3 percent via absorption . These atmospheric conditions not only reduce the quantity of energy reaching the earth's surface, but also diffuse approximately 20 percent of the incoming light and filter portions of its spectrum . After passing through the atmosphere, approximately half the insolation is in the visible electromagnetic spectrum with the other half mostly in the infrared spectrum ( a small part is ultraviolet radiation )." </li></ul>
- 16. References <ul><li>Christa McAuliffe Planetarium </li></ul><ul><li>http :// www . starhop . com / Middle / EnPath-10a ... </li></ul><ul><li>Naturetech </li></ul><ul><li>http :// www . naturetech . com . tw / </li></ul><ul><li>IPAC </li></ul><ul><li>http :// coolcosmos . ipac . caltech . edu / cosmic_classroom / light_lessons / thermal / measure . html </li></ul><ul><li>http :// hyperphysics . phy - astr . gsu . edu / HBASE / thermo / heatra . html </li></ul><ul><li>http :// www . ngdc . noaa . gov / stp / SOLAR / IRRADIANCE / irrad . html </li></ul><ul><li>http :// www . mansfieldct . org / Schools / MMS / staff / hand / convcondrad . htm </li></ul><ul><li>http :// www . atmosphere.mpg.de/enid/235.html </li></ul>

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