8.3.1 Evidence for the Expanding Universe

• What is the Big Bang Theory?

  Origin of the universe
• What is the cosmic microwave background (CMB)?

  Leftover radiation from expansion
• What is the Steady State Theory?

  Constant density universe
• What does the amount of redshift indicate about a galaxy?

  Its distance
• Redshift is observed when galaxies move closer to the observer.

  False
• Match the type of shift with its effect on light:

  Redshift ↔️ Shifts light towards red

  Blueshift ↔️ Shifts light towards blue
• Blueshift occurs when an object is moving towards the observer.


  True
• Redshift causes light to shift towards the red end of the spectrum
• The Hubble law relates redshift to the distance
• Galaxies with higher redshift are farther away from Earth.

  True
• The Big Bang Theory proposes that the universe began from an initial singularity
• What is redshift caused by?

  Doppler effect
• The Big Bang Theory suggests the universe began from an infinitely small and hot point called the initial singularity
• Redshift observations support the Big Bang Theory by showing galaxies are moving away from us.


  True
• Redshift is a form of the Doppler effect, where the wavelength of light stretches as an object moves away from the observer.
• Order the key events in the Big Bang Theory:

  1️⃣ Initial singularity

  2️⃣ Rapid expansion

  3️⃣ Formation of elements

  4️⃣ Clustering of galaxies

  5️⃣ Cosmic Microwave Background
• What happens to the wavelength of light when an object undergoes redshift?

  It increases
• When the wavelength of light increases, the frequency decreases
• What is the Doppler Effect?

  Change in wave frequency
• The Doppler Effect provides evidence for the expanding universe model.


  True
• What does $H_{0}$ represent in the Hubble law?


  Hubble constant
• What is the Big Bang Theory?

  Origin of the universe
• The cosmic microwave background (CMB) supports the Big Bang Theory.

  True
• The observed redshift indicates that distant galaxies are moving away
• Match the effect with its change in light:

  Redshift ↔️ Wavelength increases

  Blueshift ↔️ Wavelength decreases
• The Doppler Effect is the change in the observed wavelength or frequency of a wave due to relative motion
• Light from an object moving away from an observer undergoes redshift.

  True
• What happens to light when an object is moving towards the observer?

  Blueshift
• Match the concept with its effect on light:

  Redshift ↔️ Light shifts towards the red end of the spectrum

  Blueshift ↔️ Light shifts towards the blue end of the spectrum
• Order the following concepts based on their role in the Big Bang Theory

  1️⃣ Doppler Effect

  2️⃣ Redshift

  3️⃣ Expanding universe
• The Hubble law supports the expanding universe model.


  True
• What is the formula that relates observed and emitted wavelengths in redshift?

  $\lambda_{observed} > \lambda_{emitted}$
• Match the characteristic with the type of shift:

  Wavelength increases ↔️ Redshift

  Frequency increases ↔️ Blueshift
• What does the Hubble law describe?

  Recessional velocity and distance
• The Hubble constant, denoted as H_0, is a proportionality factor in the Hubble law.
• Astronomical observations reveal redshift in the light from distant galaxies.
• The Cosmic Microwave Background is the leftover radiation from the Big Bang.

  True
• What is the approximate temperature of the Cosmic Microwave Background?

  2.7 Kelvin
• The CMB exhibits a redshift consistent with the expansion of the universe.
• What is the main evidence against the Steady State Theory?

  Cosmic Microwave Background