There are two classesof planets in our solarsystem: terrestrial andjovian.
Terrestrial planets:• The “earth-like” planets. “Terra” is anothername for Earth.• Mercury, Venus, Earth & Mars.• Terrestrial planets are small, “rocky”, highdensity & orbit close to the sun.• Someday, humanity may colonize the otherterrestrial planets for the benefit ofHumankind!
Earth: the“goldilocks” planet• Not too hot, nottoo cold.• The only planetthat can haveliquid water onits surface.• The only planetwe know thathas life.
Earth moves in two ways:Rotation:The Earth spinning onits north-south axis.The earth rotates at 150per hour. After 24hours, it has turned3600 (one full turn)
Earth moves in two ways:Revolution:The Earth’s slightly ellipticalorbit around the Sun.The Earth revolves about10 per day. After 365 1/4days, it has made a fullorbit around Sol.Rotation: earth rotates onits axis.
The 2 main evidence of earth’srotation:1.Foucaultspendulum2.The Coriolis effect
a Foucaults pendulum seems tochange directions is one proof ofEarth’s rotation.
The coriolis effect: the winds seem tocurve proof that earth rotates.
Jovian planets• The “Jupiter-like” planets. Jove was anothername for Jupiter.• Jupiter, Saturn, Uranus, Neptune.• They are very large, low density, madecompletely of gases such as Hydrogen, helium,methane & ammonia.• They used to all be called: “the gas giants”• Jupiter and Saturn are called the “gas giants”• Uranus and Neptune are the “ice giants”
During the scienctific revolution (therenaissance), Copernicus, Kepler, Galileo& Newton developed the heliocentricmodel: which showed that Earth is not thecenter of the universe; Earth revolvesaround the sun.
By the early 20th century, peoplerealized that our sun is only one ofbillions of other stars in the milky waygalaxy!
definition:Galaxy: A mass ofbillions of stars. Ourhome galaxy is called“the milky way”
A typical spiral galaxyThese arecalledspiralarms
The universe has countlessbillions of galaxies!
definition:The universe is :All ofexistence, all ofcreation, everything.
Big bang theory• Developed by astronomers, who builtupon Hubble’s discoveries.• the Universe formed from a singleinfinitely dense particle called a“singularity” that “exploded” 13.7billion years ago.• This explosion is why the universe isexpanding.
Two evidence of the bigbang:1.***The “red shift” of light.2.The cosmic microwavebackground radiation.