A History of the Universe

Astronomy 315Professor Lee

CarknerLecture 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

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?

The Solar System

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

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

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

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

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

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

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

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

Composition of the Universe

Galaxies made up of: “Normal” stars (maybe with planets) Gas (hydrogen) and dust (heavier

elements)

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

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

Next Time

Read Chapter 1.1-1.5 Meet in Planetarium on Friday!