U1S2 Expanding Universe

Earth Science

What is dark energy?

A type of energy that opposes gravity and causes the expansion of the universe.

What is a planetesimal?

A small planet-like object that can combine with others to form planets.

What is the Doppler effect?

A change in wavelength of a wave due to the source and observer moving closer or farther apart.

What is dark matter?

A type of matter that fills space and is undetectable at the moment.

What is a solar nebula?

The portion of a nebula that remains after the formation of a protostar.

What is the big bang?

A massive explosion from which the universe originated about 13.7 billion years ago.

What makes up the universe?

Space and all things in space, including galaxies, stars, star systems, clusters, gas, dust, and solar systems.

What does a solar system include?

A star and all objects that orbit it, such as planets, moons, asteroids, and comets.

What is matter?

Anything that takes up space and has weight.

What is energy?

The ability to do work.

When did the big bang occur?

About 13.7 billion years ago.

What elements formed after the big bang?

Hydrogen and helium.

What did the universe form after the big bang?

Stars and galaxies.

What is red shift?

Light from a galaxy moving away from Earth appearing stretched into longer wavelengths toward the red end of the spectrum.

What is blue shift?

Light from a galaxy moving toward Earth appearing compressed into shorter wavelengths toward the blue end of the spectrum.

Who was Edwin Hubble?

An American astronomer who discovered galaxies outside the Milky Way and formulated Hubble's law.

What does Hubble's law state?

The farther away a galaxy is, the faster it is moving away from us.

What did Hubble's findings support?

The big bang theory.

What is cosmic background radiation?

Leftover thermal energy from the big bang, detected uniformly in all directions.

When was cosmic background radiation discovered?

1965

When did the solar system form?

About 5 billion years ago.

How did the solar system form?

From the collapse of a solar nebula due to gravity, forming a rotating disk with the Sun at the center.

What percentage of the solar system's matter is in the Sun?

About 98%.

How do astronomers estimate the age of the universe?

By studying background radiation patterns, galaxy speeds, and the age of the oldest stars.

What are inner planets?

Mercury, Venus, Earth, and Mars; small terrestrial planets formed near the Sun.

What are outer planets?

Jupiter, Saturn, Uranus, and Neptune; large gas giants formed farther from the Sun.

What is gravitational condensation?

The formation of solid particles from solar nebula materials.

What is accretion?

An increase in the size of an object as materials are added.

How do planetesimals form planets?

They collide, stick together, and grow larger, forming protoplanets and eventually planets.

What is dark energy's effect on the universe?

It causes the expansion of the universe to accelerate.

What are possible futures of the universe?

It may continue to expand, become dark and cold, or collapse back together.

Who was Vera Rubin?

An astronomer who provided evidence for the existence of dark matter.

What is dark matter?

Invisible matter that does not emit electromagnetic radiation but has gravitational effects.

What do scientists know about dark matter and dark energy?

Very little is known; their properties remain largely a mystery.