A History of the Universe

1
A History of the Universe

• Astronomy 315
• Professor Lee Carkner
• Lecture 2

2
Practice Observing

• Write your name (clearly!) at the top of each
  exercise!
• Label all constellations and bright stars
• Always face due N or S
• Always fill in completely Object, Location, Date
  and Time and Notes

3
Our Place in the Universe

• Before we look at the history of the universe, we
  will look at our place in it
• We now realize that we occupy no unique or
  special place in the universe
• After Nicolaus Copernicus who theorized that the
  sun, and not the Earth, was the center of the
  solar system
• So where are we?

4
The Solar System
5
Where Do We Fit In?

• We can think about our position in the universe
  in terms of scale
• Planet is in a planetary system around a star
  (Solar System)
• Galaxy is in a cluster (Local Group)
• Supercluster is in a (the?) universe
• Each step up is a huge increase in size

6
Scale Models

• We want to make a scale model to try to
  understand astronomical distances
• Need to find the scale
• example miles per inch or light years per cm
• Once you have the scale you can find the model
  size for any real object
• (model size) (real size) / scale

7
The Big Bang

• The best model for the beginning of the universe
  is the hot big bang model
• Key points
• The early universe was very hot
• Th
• Why do we believe this?
• The universe looks like it is expanding from a
  hotter, denser state

8
About the Big Bang

• We can see the expansion of the universe and the
  glow of the early hot universe
• The universe has a beginning but no center or
  edge
• The universe is not really like any macroscopic
  object we are familiar with

9
The First Three Minutes

• What was the early universe like?
• What do we know?
• Universe consists of photons and subatomic
  particles (like quarks)
• Universe went through an early period of very
  rapid expansion called inflation
• Cooled to the point where atoms could form after
  about 1 million years

10
Formation of Structure

• After about 1 billion years the universe is a big
  ball of atoms and photons
• Why?
• This is why we have matter organized into stars,
  galaxies and clusters of galaxies, instead of a
  big uniform cloud of stuff

11
The Early Stars

• The first stars were made out of hydrogen and
  helium, the two simplest elements
• Nuclear reactions inside the stars produced
  heavier elements
• Most of the universe (80) is still hydrogen,
  however

12
Stellar Products

• The next generation of stars had small amounts of
  these heavier elements in them
• When any star dies it leaves behind a burned out
  core
• Collectively known as compact objects

13
Composition of the Universe

• Galaxies made up of
• Normal stars (maybe with planets)
• Gas (hydrogen) and dust (heavier elements)

14
The Future

• What effects the future of the universe?
• Mass
• If universe has enough mass, gravity might stop
  expansion
• Dark energy
• If there is enough dark energy it might rip
  universe apart

15
The Fate of the Universe

• Possible ends for the universe
• Big Crunch
• Gravity pulls universe back into a point source
• Big Rip
• Dark energy rips universe apart
• Big Chill
• Universe expands forever

16
Next Time

• Read Chapter 1.1-1.5
• Meet in Planetarium on Friday!