Planet EarthWhat would alien astronomers observe?Chapter 4Page 109-112

A Good Place to LivePosition in the solar systemDistance from sun, nearly circular orbit, axis tilt Distance from Sun (Page 110)Average = 1.496 X 108 km (93,000,000 miles)Maximum = 1.521 X 108 km Minimum = 1.471 X 108 km Balance between size and intensity of the sun and the distance from the sun. Page 432 Goldilocks- not too hot, not too cold, just rightToo close= too hotToo far = too coldJust right for life as we know it.

Other Convenient FactsOrbital Eccentricity = 0.017Very close to circularNo extremes of temperatureAxis tilted 23.50Smears the climate

DiversityLarge blue areas and brown areasSome green areas but these change Whirling clouds in the atmosphereReflects 37% of incident sunlightPretty brightAlbedo 0.37Albedo varies with timeWhite areas at polesChange during the year

ActiveSeasonal changesPolar ice capsGreen/brownGeologically activeEarth quakesVolcanoesRiver erosionMountain formation

AtmosphereAtmosphereOxygen, Water, Carbon DioxideBut not too much Nitrogen mostlyReflects and absorbs just the right amount of electromagnetic waves

AtmosphereNitrogen 78%Oxygen 21%Argon 0.93%Carbon Dioxide .03%

ComponentSymbolVolumeNitrogenN278.084%99.998%OxygenO220.947%ArgonAr0.934%Carbon DioxideCO20.033%NeonNe18.2 parts per millionHeliumHe5.2 parts per millionKryptonKr1.1 parts per millionSulfur dioxideSO21.0 parts per millionMethaneCH42.0 parts per millionHydrogenH20.5 parts per millionNitrous OxideN2O0.5 parts per millionXenonXe0.09 parts per millionOzoneO30.07 parts per millionNitrogen dioxideNO20.02 parts per millionIodineI20.01 parts per millionCarbon monoxideCOtraceAmmoniaNH3trace

Troposphere0 11 Km (approximately 7 miles)Sheet of paper wrapped around a globeWeather occurs hereJets fly at the top of this regionHeat comes from the earthTemperature drops as you go up218 K = - 55 oC =-67 o F75% of mass of atmosphere

Stratosphere11 50 kmContains the ozone layer O3 Absorbs intermediate wave-length ultravioletThese rays are dangerous cause skin cancer, eye diseasesHeats up because of this absorptionTemperature rises as we go up in this layer285 K = 12 oC = 50 oFOzone layer has decreased due to chemicalschlorofluorocarbons

MesosphereTemperature again declinesminimum of 200 K = -73 oC = -103 oF

IonosphereRadiation from the sun heats and ionizes atoms in this layerThermosphereIons reflect radio waves (radio skip)

AtmosphereAtmosphereOxygen, Water, Carbon DioxideBut not too much Nitrogen mostlyReflects and absorbs just the right amount of electromagnetic waves

LithosphereGround surfacefertile soil, valuable metalsfuels

Atmospheric Windows (P 68)

Greenhouse Effect (P112)All wavelengths of electromagnetic radiation reach our atmosphere.Some is reflected back into space (albedo)Visible light, some ultraviolet and radio waves penetrate to surface and are absorbed.Earth is heated and then gives off infrared Infrared is absorbed by carbon dioxide, water vapor, and ozoneThis absorption heats the atmosphere

Complex ConsequencesPolar ice cap meltingRising sea levelsChanges in ocean heating and circulationChanges in weather patternsMore intense weather

Geologically Active

Alfred Wegener 1912-1915

Baby EarthLiquidSpace debris impactsRadioactive elements nuclear fissionDense material like iron settled to the centerLess dense material floated to the surfaceProduced a layered structure

Magnetic Field

Phaser Shield (p119-120)Charged particles from the sun are deflected by the magnetic field.Some of the charged particles are captured by the magnetic field forming the Van Allen beltsSometimes when there are a lot of charged particles from the sun the particles get trapped in the magnetic field at the poles and cause auroraAurora Borealis at the north poleAurora Australis at the south pole

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