Red Shift

• What is the main evidence for the universe's expansion?

  The red shifting of light from galaxies.
• What theory explains why the universe is expanding?

  The big bang theory.
• What do we need to understand before redshift?

  Absorption spectra.
• What does the absorption spectra for visible light show?

  Dark lines where wavelengths are missing.
• Why are certain wavelengths missing in the absorption spectra?

  Certain chemicals absorb specific wavelengths.
• How does the absorption spectra of distant galaxies differ from that of the sun?

  The lines are shifted towards the red end.
• What causes the redshift observed in light from distant galaxies?

  The light waves are stretched as they travel.
• If a gap was at 600 nanometers, where might it appear after redshift?

  At 650 nanometers.
• What is the misconception about galaxies moving away from us?

  They aren't moving through space; space is expanding.
• How can we visualize the expansion of the universe?

  Using a balloon with markers.
• What happens to galaxies as the universe expands?

  They get further apart from each other.
• What is a limitation of the balloon model for the universe?

  Balloons can burst, unlike the universe.
• What does the expansion of the universe imply about its past?

  The universe was smaller in the past.
• What is the generally accepted idea about the universe's beginning?

  The big bang theory.
• What does the big bang theory propose about the universe's initial state?

  All matter was in a tiny, dense, hot space.
• What happened after the initial explosion of the big bang?

  Space itself started to expand.
• What are the key concepts of redshift and the big bang theory?

  • Redshift indicates galaxies moving away.
  • Absorption spectra show missing wavelengths.
  • The universe is expanding, not galaxies moving.
  • The big bang theory explains the universe's origin.
• What are the limitations of using models to explain the universe's expansion?

  • Models can oversimplify complex phenomena.
  • Balloons can burst, unlike the universe.
  • Models may not represent all galaxies accurately.