8.3.1 Evidence for the Expanding Universe

• Red-shift occurs when light from distant galaxies is stretched
• What does Hubble's Law state?

  Velocity is proportional to distance
• Match the observational evidence with its explanation:

  Redshift of Distant Galaxies ↔️ Galaxies are moving away from us

  Cosmic Microwave Background ↔️ Early universe was hot and dense

  Abundance of Light Elements ↔️ Matches Big Bang predictions
• Red-shift shifts the light spectrum towards the red end.
• What is the equation for Hubble's Law?

  $v =$$H_{0} \times d$
• The amount of redshift increases with the distance to galaxies, supporting the expansion of the universe.


  True
• What is the equation for Hubble's Law?

  $v =$$H_{0} \times d$
• The Hubble constant is approximately 70 km/s/Mpc
• What is the primary evidence from distant galaxies that supports Hubble's Law?

  Redshift
• The observed abundance of light elements like hydrogen and helium aligns with predictions from the Big Bang nucleosynthesis model.


  True
• The uniformity of the CMB across the sky indicates the early universe was remarkably homogeneous.

  True
• What is the current estimated age of the universe?

  13.8 billion years
• What is red-shift?

  Increase in light wavelength
• Galaxies further away from us exhibit a greater red-shift than nearby galaxies.

  True
• The Hubble constant is approximately 70 km/s/Mpc.
• Arrange the steps in the process of red-shift observation and its implications:

  1️⃣ Observe light from distant galaxies

  2️⃣ Measure the increase in wavelength

  3️⃣ Calculate recessional velocity

  4️⃣ Support the expansion of the universe
• Distant galaxies exhibit a larger red-shift because they are moving away from us faster.


  True
• What observation supports the idea that the universe is expanding?

  Rapid movement away
• Hubble's Law states that the recessional velocity of a galaxy is directly proportional to its distance
• Match the term with its definition:

  v ↔️ Recessional velocity of the galaxy

  H0 ↔️ Hubble constant

  d ↔️ Distance to the galaxy
• Hubble's Law supports the expansion of the universe by showing that galaxies move away faster the farther they are.

  True
• The uniform temperature of the Cosmic Microwave Background (CMB) suggests the early universe was hot and dense
• What is the Cosmic Microwave Background (CMB)?

  Faint electromagnetic radiation
• An expanding universe implies the universe had a beginning, supporting the Big Bang theory.