Universal Universal GravitationGravitation

Any two masses mAny two masses m11 and and

mm22 separated by a separated by a

distance R are distance R are attracted by a force attracted by a force given bygiven by

F = G (mF = G (m1 1 mm22) / R) / R22

G = 6.67 x10G = 6.67 x10-11-11 Nm Nm22/kg/kg22

g = 9.8 m/secg = 9.8 m/sec22

Solar SystemSolar System

Terrestrial Planets and Terrestrial Planets and Comparative PlanetologyComparative Planetology

Variety of PlanetsVariety of Planets

Why so different?Why so different?

““Terrestrial” planetsTerrestrial” planets

““Jovian” planetsJovian” planets (=Terr + gas!)(=Terr + gas!)

The physics….The physics…. neat stuff…neat stuff…

Neat stuff to understandNeat stuff to understand

What is meant by an atmospheric gas’ What is meant by an atmospheric gas’ “temperature”?“temperature”?

Does “what goes up” Does “what goes up” havehave to come down? to come down?

Let’s see…Let’s see…

Put them Put them togethertogether

For planets plotFor planets plot

vvescesc vs. temp vs. temp

For gases plotFor gases plot <v> vs. temp<v> vs. temp

Problems with Problems with extrasolar gas extrasolar gas giants.giants.

The EarthThe Earth Famous Famous

picturepicture

Oblateness Oblateness of 0.0034 of 0.0034 (demo)(demo)

Average Average density is density is ~5.5 g/cm~5.5 g/cm33

Whereas Whereas surface surface rocks ~3…rocks ~3…

Seismology tells of interiorSeismology tells of interior

Waves from Waves from earthquakes earthquakes refracted at refracted at boundariesboundaries

Liquid and Liquid and solid inner solid inner corescores

Rotation of Rotation of liquid core liquid core leads to …leads to …

Magnetic FieldMagnetic Field

Permanent Permanent magnet magnet possible?possible?

Alternative: Alternative: currents…currents…

Magnetic FieldMagnetic Field ““Dynamo” Dynamo”

action of action of rotating liquid rotating liquid corecore

Charged Charged particles in particles in liquid core liquid core move (and move (and moving moving charges = a charges = a current)current)

Interior structureInterior structure Core heated in Core heated in

formation, kept hot formation, kept hot from natural from natural radioactivityradioactivity

Cools slower than Cools slower than smaller bodies like smaller bodies like the Moon and the Moon and Mercury (& babies)Mercury (& babies)

Convection of Convection of lithosphere leads to lithosphere leads to seismic events and seismic events and plate tectonics…plate tectonics…

Plates of the EarthPlates of the Earth

Action occurs along plate boundaries…Action occurs along plate boundaries…

VolcanoesVolcanoes

Mt. St. Helens…

Island StringsIsland Strings

Hawaiian Hawaiian IslandsIslands

How formed?How formed?

Hot Spots + Plate MotionHot Spots + Plate Motion

xxxx

EarthquakesEarthquakes

Continental DriftContinental Drift

If we back up…

Pangaea – 260 million years agoPangaea – 260 million years ago

TidesTides

DifferentialDifferential gravitational gravitational forceforce

The Moon is The Moon is twice as twice as important as important as the Sunthe Sun

Result…Result…

Tidal distortionTidal distortion

Earth itself Earth itself stretches about 9 stretches about 9 inchesinches

Tidal flow much Tidal flow much largerlarger

Two peaks (tides) Two peaks (tides) per dayper day

Sun and Moon TogetherSun and Moon Together ““Spring” tides Spring” tides

when alignedwhen aligned

““Neap” tides when Neap” tides when perpendicularperpendicular

Extra-high when Extra-high when Moon near perigee Moon near perigee and/or Earth near and/or Earth near perihelionperihelion

Births and the Moon?Births and the Moon?

Has anyone Has anyone heard that heard that birthrates birthrates depend on depend on the phase of the phase of the Moon?the Moon?

My StudyMy Study

Nope.Nope.

Nor ….

… … plotted against perigeeplotted against perigee