The universe began from a single point and has been expanding and cooling ever since.

The universe is expanding, but new matter is constantly created to keep its density the same.

The universe is unchanging and has always existed in its current state.

The universe was formed from a large cloud of dust and gas that collapsed.

The Big Bang Theory states the universe had a beginning, while the Steady State Theory suggests it is essentially unchanging over time.

The Big Bang Theory proposes the universe is shrinking, while the Steady State Theory proposes it is expanding.

The Big Bang Theory involves the constant creation of new matter, while the Steady State Theory does not.

The Big Bang Theory is the only theory that accounts for the universe's expansion.

Scientific discoveries have provided evidence that supports the claims of the Big Bang Theory.

The Steady State Theory is too old to be considered a modern scientific idea.

The Big Bang Theory is simpler to understand and explain than the Steady State Theory.

The Steady State Theory fails to explain why the universe is currently expanding.

The distance light travels in a year

The time it takes for the sun to burn out

The age of the oldest star observed

The speed of a spaceship traveling to Mars

Because their light is stretched out, making them look older

Because it takes a very long time for their light to reach Earth

Because telescopes can reverse the direction of time

Because the universe's expansion slows down time for distant objects

It measures the exact distance to every star, which reveals their age.

It provides evidence for the universe's expansion, which is used to calculate its age.

It shows the color of a star, which directly translates to its age in years.

It slows down light from distant objects, allowing for more accurate measurements.

It pushes gas and dust apart.

It causes the star to start spinning.

It pulls vast clouds of gas and dust together.

It creates the light of the new star.

The center of the nebula becomes cooler and less dense.

The nebula immediately begins nuclear reactions.

The center of the nebula becomes hotter and denser.

The nebula flattens into a disk and disappears.

A much larger star would form instead.

The nebula would start to cool down and expand.

A star would not be created because nuclear reactions would fail to start.

Gravity would become stronger and pull in more dust.

A vast system of stars, gas, and dust held by gravity

A collection of planets and moons orbiting a star

A large cloud of gas that will one day form a star

A single star and all the objects in its orbit

The main types of galaxies

The different sizes of stars

The stages in a star's life

The various colors of planets

The Milky Way is an example of a spiral galaxy.

All galaxies in the universe are spiral galaxies.

The Milky Way is the only galaxy of its type.

Elliptical and irregular galaxies are types of spiral galaxies.

A shockwave caused a gas and dust cloud to collapse.

The Sun captured existing planets with its gravity.

A large planet broke apart into smaller pieces.

Two stars collided with each other.

It gathered at the center to form the Sun.

It immediately broke apart to form the planets.

It was evenly distributed throughout the spinning disc.

It was ejected into space by the shockwave.

There would have been less material available to form planets.

The Sun would have been much smaller and cooler.

The planets would have formed much closer to the Sun.

The gas giant planets would have become rocky planets.