Astronomy and Cosmology Where does the Earth fit in?

Formation of the Earth

 Big Bang Galaxies Solar Nebulas Star Formation PlanetsBeginning of Life  Big Bang Galaxies Solar Nebulas Star Formation PlanetsBeginning of Life

Big Bang  The theory that states the universe began with a tremendous explosion  12 bya to 15 bya (billion years ago)  The theory that states the universe began with a tremendous explosion  12 bya to 15 bya (billion years ago)

What is a theory?  A theory is well-tested and supported by evidence  A theory is widely accepted by scientists  A theory can be disproved  A theory is well-tested and supported by evidence  A theory is widely accepted by scientists  A theory can be disproved

Galaxies  Large grouping of stars in space, formed when chemical clouds gathered after the Big Bang  Large galaxies contain more than a trillion (1,000,000,000,000) stars  Large grouping of stars in space, formed when chemical clouds gathered after the Big Bang  Large galaxies contain more than a trillion (1,000,000,000,000) stars

Galaxies  Contain gas clouds, open clusters, and globular clusters  Gas clouds are also known as nebulas and are generally found in spiral galaxies  Open clusters are groups of newly formed stars  Globular clusters are groups of older stars  Contain gas clouds, open clusters, and globular clusters  Gas clouds are also known as nebulas and are generally found in spiral galaxies  Open clusters are groups of newly formed stars  Globular clusters are groups of older stars

Galaxies  Types  Spiral  Elliptical  Irregular  We live in the Milky Way Galaxy  The Milky Way is a spiral galaxy  Our sun is about two-thirds of the way from the center of the Milky Way  Types  Spiral  Elliptical  Irregular  We live in the Milky Way Galaxy  The Milky Way is a spiral galaxy  Our sun is about two-thirds of the way from the center of the Milky Way

Star Formation  Gravity collects hydrogen and helium to form a star  Our sun is an average sized star  Gravity collects hydrogen and helium to form a star  Our sun is an average sized star

Planetary Formation  Dust gathers to form planetesimals  Biggest planetesimal in each orbit swept up all the dust in that path  Gas giants collected lots of gases because of large gravitational pull  Gases evaporated from inner planets to leave rocky planet  Dust gathers to form planetesimals  Biggest planetesimal in each orbit swept up all the dust in that path  Gas giants collected lots of gases because of large gravitational pull  Gases evaporated from inner planets to leave rocky planet

Planets  Planets rotate on its axis. One rotation is one day.  Planets also revolve around the sun. One revolution is one year.  Big enough for its gravity to make it a ball  Clear the neighborhood around its orbit  Planets rotate on its axis. One rotation is one day.  Planets also revolve around the sun. One revolution is one year.  Big enough for its gravity to make it a ball  Clear the neighborhood around its orbit

Revolution vs. Rotation

Inner Planets  Solid planets  Warmer than outer planets  Close together  Short revolution  Mercury, Venus, Earth, Mars  Solid planets  Warmer than outer planets  Close together  Short revolution  Mercury, Venus, Earth, Mars

Outer Planets GGas Giants (gaseous) CCold FFar apart LLong revolution JJupiter, Saturn, Uranus, Neptune

Dwarf Planets PPast outer planets PPluto- formerly a planet CCeres-formerly an asteroid UUB313 or Xena- discovered in 2003

The Moon  The moon does not produce its own light  It reflects light from the sun  Half the moon is always lit, even though we don’t always see the same thing in the sky  The moon does not produce its own light  It reflects light from the sun  Half the moon is always lit, even though we don’t always see the same thing in the sky

Phases of the Moon

Lunar Eclipse  The earth casts a shadow on the moon  The moon is in the full moon position  The earth casts a shadow on the moon  The moon is in the full moon position

Solar Eclipse  The moon casts a shadow on the earth  The moon is in the new moon position

Comets  Small body of ice, rock, and dust loosely packed together  Also known as “dirty snowballs”  Tail forms when comet gets too close to the sun  Elliptical orbit  Small body of ice, rock, and dust loosely packed together  Also known as “dirty snowballs”  Tail forms when comet gets too close to the sun  Elliptical orbit

Asteroids  Small, rocky bodies that orbit the sun  Irregular shapes  Different compositions based on where asteroid is found in the asteroid belt  Small, rocky bodies that orbit the sun  Irregular shapes  Different compositions based on where asteroid is found in the asteroid belt

Meteoroid  Small, rocky bodies orbiting the sun  Smaller than asteroids  A meteoroid is called a meteorite when it comes into the earth’s atmosphere and hits the ground  The streak of light that you see when a meteoroid enters the earth’s atmosphere is called a meteor  Small, rocky bodies orbiting the sun  Smaller than asteroids  A meteoroid is called a meteorite when it comes into the earth’s atmosphere and hits the ground  The streak of light that you see when a meteoroid enters the earth’s atmosphere is called a meteor

Distances  Distances are so far apart in astronomy, so we use  Astronomical Units (AU)- average distance between the earth and the sun or about 150,000,000 km (93,000,000 miles)  Light Years- distance light travels in one earth year or 9.5 trillion km (9,500,000,000,000)  Distances are so far apart in astronomy, so we use  Astronomical Units (AU)- average distance between the earth and the sun or about 150,000,000 km (93,000,000 miles)  Light Years- distance light travels in one earth year or 9.5 trillion km (9,500,000,000,000)

Other Stars…?  Our nearest star is Alpha Centauri  It is 4.27 light years away or 40,565,000,000,000 km  Our nearest star is Alpha Centauri  It is 4.27 light years away or 40,565,000,000,000 km