5.1.4 The Big Bang and the Fate of the Universe

​The Big Bang and the Fate of the Universe
5.1.4

By Caitlin Ford

Objectives

• discuss the Big Bang Theory

• list the evidence for the Big Bang Theory

• describe the distribution of galaxies in the universe

• explain the fate of the universe

How did the Universe begin?

Any theory explaining the origin of the universe has to explain three things:

- The laws of physics must be followed throughout the universe.
- The universe has roughly the same composition in all directions.
- The universe is expanding.

The Big Bang Theory

Electrons, protons, and neutrons formed. Then atoms. Then molecules.

After billions of years, larger structures were formed, like stars and galaxies.

The Big Bang was not an explosion that destroyed. It was a rapid expansion that formed the universe!

The Big Bang Theory

1926 - Georges Lemaitre developed the Big Bang Theory.

He said the universe started from a single point that underwent rapid inflation.

In a fraction of a second, the point grew 10,000 times its size.

As it cooled, matter, energy, light, and gravity formed.

Dropdown

According to the Big Bang theory, the universe originated from the​

Select answer

of a single point.

Clusters

After 3 billion years, galaxies started grouping together.

The Milky Way belongs to a cluster of 50 galaxies called Local Group.

The Timeline

The Big Bang happens.

The single point rapidly inflates. (a microsecond)

Inflation stops, and cooling starts. (a few microseconds)

Electrons, protons, and neutrons form (1 second)

Particles merge to make elements (3 seconds)


Complex and stable elements form. Radiation separated from the matter and began to travel freely. (380,000 years) The remains of this radiation form the cosmic microwave background radiation, the oldest light of the universe.

The Dark Ages. Matter merges with dark matter. Stars and galaxies form. (100 millions years)

Clusters and superclusters. (10 billion years)

Superclusters

Local Group is gravitationally bound to other clusters, which forms a supercluster.

The Virgo Supercluster contains the Local Group, several other clusters, and isolated galaxies.

Clusters and superclusters are not evenly distributed. Some areas are empty regions - voids.

Multiple Choice

What is the Local Group?

• a group of galaxies located within 20,000 light years from the Milky Way galaxy

• a supercluster of galaxies that contains the Milky Way galaxy

• a cluster of galaxies which contains the Milky Way galaxy

• a group of stars located within 20 light years from the Sun

Evidence for the Big Bang Theory

Redshift - galaxies are moving away from the Milky Way. The universe is expanding. Tracing their paths backward shows they all originated from a single point.

Cosmic Microwave Background Radiation - traces of the enormous head formed by the Big Bang.

Traces of Elements - older stars contain heavier elements. Our sun only contains hydrogen and helium, because it is fairly young.

The Observable Universe

The observable portion of the universe is a sphere with a diameter of 93 billion light-years. This observable universe is centered around the Virgo supercluster.

The inconsistency with the age of the universe (14 billion years) and the observable universe (93 billion light years) is due to the universe's expansion.

The Fate of the Universe

Gravity - if the force of gravity is strong enough, it will slow the expanding universe and could even cause it to contract.

If the force of gravity is too weak to stop the expansion, the universe will continue to expand.

Current calculations show that gravity cannot stop the expanding universe. It will keep expanding, galaxies will move further a part, stars will burn out and new stars will stop forming.

The universe will go dark and all matter will fall into black holes. This is called the Big Freeze.

Reorder

Order the events of formation according to the Big Bang Theory.

• rapid inflation

• protons, neutrons, and electrons

• elements

• dark matter

• clusters and superclusters

1

2

3

4

5

• 1
• 2
• 3
• 4
• 5

Dropdown

Evidence for the Big Bang theory includes:

​

Select answer

- galaxies are moving away from the Milky Way

​

Select answer

- traces of heat formed by the Big Bang

​

Select answer

- the distribution of heavier ones in older stars and lighter ones in younger stars

Great job!

Today, you learned:

- the Big Bang theory
- evidence for the Big Bang theory
- the distribution of galaxies in the universe
- the fate of the universe.