Galaxies and the Expanding Universe

These flashcards cover key concepts related to galaxies, their motion, red-shift, and the implications on the understanding of the expanding universe and the Big Bang theory.

What happens to the motion of a galaxy the further away it is?

The further away a galaxy is, the faster it is moving.

What is observed about the wavelength of light from more distant galaxies?

The greater the observed increase in wavelength.

What does red-shift provide evidence for?

It provides evidence that the universe is expanding and supports the Big Bang theory.

What does the Big Bang theory suggest about the universe's beginnings?

The entire universe started from a very small, hot and dense region in space.

How does the observed red-shift of galaxies compare with distance?

The observed red-shift is greater the further away the galaxy is.

What was observed that indicated the universe is expanding at an ever faster rate?

Scientists observed supernovae suggesting galaxies are moving away at an ever faster rate.

What was the prior belief about the rate of expansion of the universe?

The rate of expansion was expected to occur at an ever slower rate.

What caused the prior belief about the universe's expansion rate?

It was thought that gravitational forces would cause the slowing down.

What ideas could explain the increasing rate of the universe's expansion?

The existence of undetectable energy and mass known as dark matter and dark energy.

What is dark matter?

Mass that cannot be observed directly but is thought to exist due to gravitational effects.

What is dark energy?

A form of energy hypothesized to be responsible for the accelerated expansion of the universe.

What indicates that galaxies might be moving away from us?

The red-shift in the light emitted by distant galaxies.

How does the expansion rate relate to supernovae observations?

Supernovae observations suggested galaxies are moving away at an ever faster rate.

What observations contradicted previous beliefs about expansion rates?

Observations of supernovae contradicted the belief that the expansion rate was slowing.

What is one characteristic of light emitted from distant galaxies?

It shows a greater red-shift compared to light from closer galaxies.

Why do scientists think the universe's expansion is accelerating?

Due to observations of supernovae and the implications of red-shift data.

What early models of the universe predicted slower expansion?

Models that included the effects of gravitational forces.

What is the significance of the concept of red-shift?

It helps astronomers determine the velocity and distance of galaxies from Earth.

What does the phrase 'the universe is expanding' mean?

It means that galaxies are moving away from each other over time.

What type of evidence supports the Big Bang theory?

Cosmic microwave background radiation and the red-shift of distant galaxies.