Origin of the Universe

Universe = the totality of all the things that exist

There are 2 main theories for the origin

of the universe:

1. Big Bang Theory- the universe

began as a point and has been

expanding ever since.

2. Steady-state Theory- the universe

has always existed and does not

change with time.

When you look out into space, you are looking back in time.

The farther out you look the farther back in time you see.

Some of the stars you see may no longer exist!

The light from these stars left them long ago and is only now

reaching Earth.

Light that you see from the sun left the surface of

the sun about 8 minutes ago!

Big Bang Theory

Big Bang Theory Timeline

Time Event

0 - 0.01 Universe grew from size of a pin head to

second 2000 times size of the sun

Temperature = billions of degrees

1 second First elementary particles form (electrons, protons,

neutrons)

3 - 4 First atoms form (Hydrogen and Helium)

seconds Temperature = 900 million degrees

300,000 Matter condensed into clumps and formed

years first galaxies

Temperature = 4,000 degrees

1 billion years First stars formed

~10 billion Milky Way Galaxy formed

years

Milky Way Galaxy

Evidence to support the Big Bang:

1. Light coming from distant galaxies

indicates that the universe is expanding uniformly-

all points are moving away from all other points.

Uniform Expansion

2. Cosmic background radiation was detected in

1965 by a radio antenna at Bell Labs, Holmdel, NJ.

The background “noise” comes from all directions

and can be explained to be the result of

leftover radiation from an early, very hot universe.

Evidence to support the Big Bang:

Cosmic Background Radiation Discovered

Cosmic Background Radiation

Age of the universe:

The age of the universe can be found if you

know the rate of expansion of the universe

(H = Hubble constant).

• If the expansion rate is relatively slow, the

universe is relatively ___?___

• If the expansion rate is relatively fast,

the universe is relatively ___?___

The universe is thought to be 13 to 15 billion

years old.

What is the universe made of?

Lithium Atom

Astronomers think the universe is made up of only

three things:

1. Atoms (4%)- “normal matter.”

The stars and planets account for only 0.4%

of the universe.

Eagle Nebula

Intergalactic gas, or nebula, makes up 3.6%

Orion Nebula

Black Hole

2. Dark Matter (22%)- matter that does not give off

light but has gravity. Black holes are a type of dark

matter. They are so dense and massive that their

gravity pulls everything in, including light.

Nothing escapes!

Milky Way Galaxy

3. Dark Energy (74%)- a force that opposes gravity.

Scientists know almost nothing about dark energy.

It appears to be pushing galaxies apart, causing the

rate of expansion of the universe to accelerate-

speed up!

http://home.fnal.gov/~gnedin/cc/