Ptolemaic theory (geocentric) Copernicus’s theory (heliocentric)

Theories about the center of the universe A theory is an explanation of related observations. Geocentric EARTH centered (sun, moon, stars, planets revolve around Earth) Believed until 1500 AD Early cultures and Ptolemy Heliocentric Sun centered (planets and comets revolve around the sun) 1500 AD ~ present Copernicus*, Galileo, Kepler, Newton Are either correct? - Helio is mostly correct

Review Question What did the geocentric theory state? Is this theory correct? >>Earth is at the center of the solar system (incorrect)

Big Bang Theory (theory of the formation of the Universe --1950) BrainPop: Big Bang matter, time, and energy were compressed into an extremely small ball(very unstable) also called a singularity, then exploded about 13-14 BILLION years ago, this explosion is called a Supernova The leftovers from the supernova is called a nebular cloud. It contains the gas & dust particles from the explosion, and is expanding outward DYK: Every hour the Universe expands by a billion miles in all directions.

Nebular Theory The most widely accepted theory on solar system formation is the NEBULAR THEORY States that the solar and stellar systems were developed from an ancient nebula due to the process of accretion. Protostar

Planetesimals form due to the accretion (clumping together) Nebular Theory remember, nebulae develop from supernovas called a star when fusion begins in core (about 10m°K) Stars begin as a protostar (baby star) in a nebula (gas/dust cloud from old stars) Planetesimals form due to the accretion (clumping together) of dust/gas particles that are in orbit around a protostar, eventually forming a planet Protostar

…after about 10 billion years, the star becomes a MAIN SEQUENCE star, where it spends most of its life this is the stage that our sun is in (as well as most stars) hydrogen changes to helium (nuclear fusion) in the core of the star

Rotation=SPIN (1 rotation=1 day=24 hours) The axis of Earth is an imaginary line that runs through the middle of the Earth from the North Pole to the South Pole which Earth rotates or spins around Earth is tilted on its axis at 23.5 degrees (why we have seasons) Day/night animation: http://www.classzone.com/books/earth_science/terc/content/visualizations/es0404/es0404page01.cfm?chapter_no=visualization

N I G H T D A Y

Revolution= movement around one object by another object Note: all of our planets revolve counter~clockwise around the Sun orbit is the PATH the planet (or moon) takes as it revolves shape of orbit is circular or elliptical (oval) Ex: one revolution/orbit around the sun=1 year=365.25 days Ex: one revolution/orbit of the moon around the Earth=1 month

GRAVITY depends on: MASS and DISTANCE INERTIA Newton's First Law of motion states that an object will remain at rest or in motion (same direction) unless acted upon by an outside force. elliptical INERTIA GRAVITY depends on: MASS and DISTANCE BrainPop: Newton

Earth in Space Earth revolves rotates On its axis Around the sun Resulting in Years Day & night

Earth in Space March=Vernal Equinox September=Autumnal Equinox BrainPop: Seasons March=Vernal Equinox September=Autumnal Equinox June=Summer Solstice December=Winter Solstice

Our Solar System (includes the sun, 9 planets and their moons, asteroids, comets, meteoroids & other smaller objects)

Our star, THE SUN yellow middle-aged (main sequence) medium-sized surface temperature of about 6000°C medium brightness

SUPERGIANTS (on Orion’s shoulder) GIANTS

Planets Inner Planets Outer Planets Other… also called terrestrial planets small, dense and rocky no rings Mercury Venus Earth Mars Outer Planets also called gas giants or Jovian planets all have moons all have at least one ring Jupiter Saturn Uranus Neptune Other… Pluto (reclassified as a dwarf planet)

Relative size of the planets

Comets ~small body of ice, rock, and cosmic dust ~ look like “dirty snowballs” ~tail visible when comet gets close enough to the sun (points away from sun due to solar winds) ~tail can be millions of miles long, and seen for many weeks ~gets smaller with every trip (melts)

…website animation… http://www.classzone.com/books/earth_science/terc/content/visualizations/es2706/es2706page01.cfm?chapter_no=visualization (comet passage)

You can see a comet for weeks (or months)! …unlike a meteor

Asteroids dense, rocky bodies that orbit the sun (over 100,000 known)—smaller than a planet most are irregularly shaped (not round) size: few meters to 900 km most found in the asteroid belt (between Mars and Jupiter)

Ceres largest known asteroid (785 km) now considered to be a dwarf planet

Meteoroids Meteoroid= small pieces of comets or asteroids in space Meteor= burning up in the atmosphere (inaccurate to say “falling/shooting star”) Meteorite= hits the ground (MAY make a crater)

WOW!!! Meteor shower over Russia, Feb 15, 2013 http://www.youtube.com/watch?v=dBvotWfR3j4

Which one is this? What caused this? meteor meteorite

Did you know?? The mass of the earth increases every year because of the 3,000 TONS of meteorite debris that hits the surface from space! Approximately every 50-60 years, somebody is struck by a meteor; last time was in 1954 The odds of you being hit is a billion to one (no human has ever been killed by a meteor strike).

Think about it…. If we were to send a manned mission to Mars, how could we avoid getting damaged by the asteroid belt? The asteroid belt is between Mars and Jupiter. If you lived on the moon, about how many meteors would you see on the moon in an earth year? None—no atmosphere

Which of the following is a characteristic of comets? A. Comets are composed of rocky material, iron, and nickel. B. Comets follow a circular orbit around the sun. C. Comets give off gas and dust when heated by the sun. D. Comets are rich in iron.

Which of the following is a wide region of small, rocky bodies that is located between the orbits of Mars and Jupiter? A. the Kuiper belt B. the Oort cloud C. the asteroid belt D. the rings of Saturn

When it approaches the sun, which object produces a shimmering tail that lasts at least a few days? a comet In which direction does a comet’s tail always face? away from the sun

Where are most asteroids found? in orbit between Mars and Jupiter What is the sequence that describes a space rock that falls to Earth’s surface? meteoroid, meteor, meteorite

Which one of the following objects in our solar system would travel the greatest distance during one revolution around the sun? A. a terrestrial planet B. an asteroid C. a gas giant D. a comet