The Big Bang 15 20 billion years ago

The Big Bang! 15 -20 billion years ago

The Big Bang Theory: • Occurred ~ 15 -20 billion years ago • Before the Big Bang, there was NOTHING! • All of time, space, energy and matter were compressed into something smaller than an atom

• After the Big Bang, all of this energy and matter were released, forming the galaxies, stars, planets, and other celestial objects in the universe

• The entire universe is ~ 25 billion light years in diameter and is still expanding!

100, 000 years after the Big Bang Clouds of hydrogen and helium

The Fate of the Universe? • Some scientists think that the universe will continue to expand forever (red shift)

• Others think that the force of gravity will eventually reverse the expansion and the universe will fall back together (blue shift) –This will be called the BIG CRUNCH!!!

The 2 possible fates of our Universe….

The collision between the Milky Way and the Andromeda Galaxy

Evidence for Big Bang: 1. Background Radiation (echo) – -crackling noises detected from space -noise from the Big Bang

wavelength Moving Towards? Moving Away?

Electromagnetic Spectrum According to the ESRT, which has a longer wavelength – blue or red? RED!!!

Doppler Effect – Stars from distant galaxies are emitting light in longer wavelengths (towards the red end of the spectrum)

This indicates that they are moving away from each other Red Shift = our universe is expanding

• Blue shift = when a star or galaxy is moving towards you

The Doppler Effect

Standard Closer = Blue Shift Further away = Red Shift

The Visible Spectrum The Absorption Spectrum The Emission Spectrum A Red Shift A Blue Shift

Water from volcanoes The Birth of today’s Earth 4. 5 bya Water from meteors crashing into Earth.

Formation of Life 3. 5 bya Blue-green algae 1 st plants used the CO 2 in the atmosphere for photosynthesis creating OXYGEN!

Early Models of the Universe Ptolemy

Basic Geocentric View Celestial Sphere Saturn E Mercury Jupiter Mars Moon Venus Sun

The Geocentric Universe • Ancient people (Aristotle) “knew” from observations that – The stars appear fixed on the sky relative to each other. – Planets, moon and sun change position with respect to the stars. – Mercury and Venus only seen near sun. • These observations led them to theorize that the Earth is at the center and all objects move around it. • Earth DOES NOT MOVE! After all, can you feel it moving?

Problem: Retrograde motion of Mars • Planets usually move from west-to-east in the sky with respect to the stars over long periods of time. • Sometimes planets go east-to-west in sky=retrograde motion. Note: Retrograde motion was very hard to explain Main challenge to ancient models of the solar system.

Retrograde Motion

• Ptolemy – Created the idea of epicycles. • Predicted the position of the planets accurately with some problems. • Theory lasted 15 centuries. Solution!

Retrograde motion explained! But what about those other planets whose position could not be accurately determined?

So what happened to this theory… The model became so complicated that they had to come up with a new idea! Too many epicycles!

Nicholas Copernicus (14731543) • Heliocentric (sun centered) model of the Solar System. • More simply predicted paths of planets

Basic Heliocentric View Celestial Sphere • Heliocentric Model = sun at center • All planets orbit the sun • Moon orbits the Earth. • Circular orbits E S M S V M J

Retrograde motion in action!

How would the distance a planet is from the sun affect its period of revolution? • The closer a planet is to the sun the shorter it takes to go around the sun. Closest planet Mercury only 88 days to make it’s trip around the sun. • The farther a planet is from the sun the longer it takes to go around the sun. Neptune takes 164. 8 years to make it’s trip around the sun.