7.3 The Expanding Universe

• The Expanding Universe is the scientific theory that the universe is continuously expanding and growing in size
• The part of the universe we can see is called the observable universe
• What does redshift indicate about the movement of distant galaxies?

  They are moving away
• Which theory of the origin of the universe incorporates the Expanding Universe concept?

  Big Bang theory
• What is redshift defined as?

  Stretching light wavelengths
• Why is redshift considered a crucial piece of evidence for the expanding universe?

  Galaxies are moving away
• What is the formula for Hubble's Law?

  $v =$$H_{0} \times d$
• What is the term for the speed at which a galaxy is moving away in Hubble's Law?

  Recessional velocity
• The Cosmic Microwave Background Radiation was discovered in 1965 by Arno Penzias and Robert Wilson.
• The Expanding Universe theory states that the distance between galaxies is continuously increasing.


  True
• Edwin Hubble first proposed the Expanding Universe theory in the 1920s.


  True
• Match the evidence with its description:

  1️⃣ Redshift ||| Indicates that galaxies are moving away from us

  2️⃣ Hubble's Law ||| The velocity of a galaxy's recession is proportional to its distance: $v =$$H_{0} \times d$
• The CMB was discovered in 1965 by Arno Penzias and Robert Wilson.


  True
• The CMB provides a snapshot of the universe approximately 380,000 years after the Big Bang.


  True
• Edwin Hubble first proposed the concept of the Expanding Universe in the 1920s.


  True
• The Big Bang theory explains the universe's origin from a hot and dense state about 13.8 billion years ago.


  True
• Stages in the timeline of the universe's evolution

  1️⃣ Big Bang

  2️⃣ Expansion

  3️⃣ Recombination

  4️⃣ Formation of Structures

  5️⃣ Present Day
• What is one key feature of the Expanding Universe?

  Continuous expansion
• Match the evidence for the Expanding Universe with its description:

  Red Shift ↔️ Light from distant galaxies shifts towards the red end of the spectrum

  Hubble's Law ↔️ The velocity of a galaxy receding is proportional to its distance
• Redshift occurs because distant galaxies are approaching Earth.

  False
• Redshift provides observational evidence for the Expanding Universe.


  True
• Redshift provides direct observational evidence for the expanding universe.
• Hubble's Law states that the velocity of a galaxy moving away from us is directly proportional to its distance from us.


  True
• What does \( H_0 \) represent in Hubble's Law?

  Hubble constant
• What is the Cosmic Microwave Background Radiation (CMB)?

  Remnant heat from Big Bang
• Match the feature of the CMB with its description:

  Definition ↔️ Residual thermal radiation from the Big Bang

  Discovery ↔️ Discovered in 1965 by Arno Penzias and Robert Wilson

  Significance ↔️ Provides evidence for the Big Bang theory
• What happens to the observable universe as it expands?

  Gets larger
• Hubble's Law mathematically confirms the Expanding Universe theory.
• What is the Cosmic Microwave Background Radiation (CMB)?

  Remnant heat from Big Bang
• What is the significance of the CMB?

  Evidence for Big Bang
• The universe is expanding at an accelerating rate over time.
• The redshift and Hubble's Law both support the Expanding Universe theory.
• Around 380,000 years after the Big Bang, atoms formed during the stage called recombination.
• The distance between galaxies is decreasing as the universe expands.

  False
• The Expanding Universe theory was first proposed by Edwin Hubble in the 1930s.

  False
• Hubble's Law is described by the equation $v =$$H_{0} \times d$, where `v` is the recessional velocity
• Redshift shifts light towards the red end of the electromagnetic spectrum
• The cause of redshift is the expanding universe, which makes distant galaxies recede from Earth.


  True
• Match the concept with its description:

  Definition ↔️ The stretching and shifting of light wavelengths towards the red end of the spectrum

  Cause ↔️ The Expanding Universe causing distant galaxies to recede from Earth

  Significance ↔️ Provides direct evidence for the Expanding Universe theory
• In Hubble's Law, \( v \) represents the recessional velocity of a galaxy.