Solar Energy to Earth and the SeasonsThe Solar System, Sun, and EarthSolar Energy: From Sun to EarthThe Seasons

The Solar System, Sun, and EarthSolar System formation and structureGravityPlanetesimal hypothesisDimensions and distancesSpeed of lightEarths orbit

GravityMutual attracting force exerted by mass on all other objects: Solar System Formation and StructureG 6.674281011 m3/(kgs2).F: kg*m/s2 =1 Newtong=9.8 m/s2

Planetesimal hypothesisSun condensed from nebular clouds 4.6 billion years ago. Big Bang ~13 billion years ago.

Solar System Formation and Structure

Milky Way GalaxyFigure 2.1

Dimensions and DistancesSpeed of light299,792 km/s(3.0108m/s) (186,282 mi/s)Milky Way Galaxy 100,000 ly acrossOur Solar System 11 light-hours acrossMoon is 1.28 light-seconds away

Dimensions and DistancesEarths orbitAverage distance from Earth to the Sun is 150,000,000 km (93,000,000 mi)Perihelion closest at January 3147,255,000 km (91,500,000 mi)Aphelion farthest at July 4152,083,000 km (94,500,000 mi)Earth is 8 minutes 20 seconds from the SunPlane of Earths orbit is the plane of the ecliptic

Our Solar SystemFigure 2.1

Pluto not a Planet since 2006Figure 2.1New Definition by International Astronomical Union in 2006:

A planet is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.

Pluto is now called a Dwarf Planet on account of its size and the fact that it resides within a zone of other objects, known as the Kuiper Belt

A dwarf planet is an object in orbit around the Sun that is large enough (massive enough) to have its own gravity pull itself into a round (or nearly round) shape. Generally, a dwarf planet is smaller than Mercury. A dwarf planet may also orbit in a zone that has many other objects in it. For example, an orbit within the asteroid belt is in a zone with lots of other objects.

Solar Activity and Solar WindDiameter 1,392,000km (~109 Earths diameter ), Contain 99.86% of mass in solar system.3/4 of Sun is hydrogen, the rest is helium (

The Electromagnetic SpectrumSun radiates shortwave energy Plancks Law: Blackbody spectral radiant emittance Where h: Planck Constant, 6.626E-34 ws2 c: speed of light in vacuum 3.0E+8 m/s : wavelength in meters T: temperature in degrees Kelvin K: Boltzman constant, 1.38054E-23 ws/K M: blackbody spectral exitance at T, unit = watts per square meter area per meter wavelength

The Electromagnetic Spectrum Stefan-Boltzmanns Law:Where is Stefan-Boltzmann constant (5.676E-8wm-2K-4)

The Electromagnetic SpectrumWiens Law: The wavelength at which a blackbody radiates most energy:A=2.898E-3 mK

Wavelength and FrequencyFigure 2.5Frequency: number of full waves passing through a point in unit time

freq=c/

Particle PropertyParticle Properties: Radiation travels in bundles of energy unit, called photons. The photons possess particle property, most notably photons can be reflected.

EMR transfers in terms of energy packets or quanta in accordance with quantum theory. The particle that carries energy is called a photon. The amount of energy (Joules) carried by a single photon isWhere h=6.6256E-34 J/s. It is obvious, the shorter the wavelength, the more the energy a photon carries.

The total energy in a ray beam is the summation of the energy carried by all the photons that makeup the beam.Unit: JoulesUnit: JoulesEnergy of Photons

Unit: Joules/second=Watts=WUnit: Joules=JUnit of Energy Energy:Adding time energy measure: Energy fluxAdding area to energy flux: energy flux densityUnit: Joules/second/m2=W/m2

The Electromagnetic SpectrumFigure 2.6

Solar ConstantThe radiant flux density at the top of the atmosphere perpendicular to the sun beam:S=1367 w/m2EarthTop of AtmospherePlane measuring S

Solar and Terrestrial EnergyFigure 2.7

Earths Energy BudgetFigure 2.8ShortwaveReflectedRadiation Balance Equation:

Distribution of Solar Radiation on Earth SurfaceTropics receive more concentrated insolation due to Earths curvatureTropics receive 2.5 more than poles

Figure 2.9

The SeasonsSeasonalityReasons for seasonsAnnual march of the seasons

Insolation at Top of AtmosphereFigure 2.10

SeasonalitySeasonal changesSuns altitude angle above horizonDeclination location of the subsolar pointDaylength

TOA Daily Net RadiationFigure 2.11Unit: w/m2Measured by Satellite (Nimbus-7) in space.

Reasons for SeasonsRevolutionRotationTilt of Earths axisAxial parallelismSphericity

Reasons for SeasonsRevolutionEarth revolves around the SunVoyage takes one year (365.25 days more accurately)Earths speed is 107,280 kmph (66,660 mph)RotationEarth rotates on its axis once every 24 hoursRotational velocity at equator is 1674 kmph (1041 mph)

Revolution and RotationFigure 2.13

Reasons for SeasonsTilt of Earths axisAxis is tilted 23.5 from plane of eclipticAxial parallelismAxis maintains alignment during orbit around the SunNorth pole points toward the North Star (Polaris)Sphericity: not perfect sphere because of rotation, the equator is bulging out Sphericity: f = 1-short/long =1/298f=? for a perfect sphere.

Axial Tilt and ParallelismFigure 2.14Sun declination angle: -23.5~23.5o

Annual March of the SeasonsWinter solstice December 21 or 22Subsolar point Tropic of CapricornSpring equinox March 20 or 21Subsolar point EquatorSummer solstice June 20 or 21Subsolar point Tropic of CancerFall equinox September 22 or 23Subsolar point Equator

11:30 P.M. in the AntarcticFigure 2.16

Seasonal ObservationsFigure 2.1840oN

Robert W. ChristophersonCharlie Thomsen

Geosystems 7eAn Introduction to Physical Geography

End of Chapter 2

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