red shift

• What is the central idea of the video?

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

  The red shifting of light from galaxies.
• What does redshift indicate about distant galaxies?

  They are moving away from us.
• What is absorption spectra?

  Light wavelengths absorbed by chemicals.
• How does the sun's atmosphere affect the light we see?

  Certain wavelengths are absorbed, creating dark lines.
• What happens to light from distant galaxies as it reaches Earth?

  It appears shifted towards the red end.
• Why do light waves from distant galaxies get stretched?

  Because the galaxies are moving away from us.
• How does the expansion of space relate to the movement of galaxies?

  Galaxies aren't moving, space is expanding.
• How can we visualize the expansion of the universe?

  Using a balloon with markers for galaxies.
• 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.
• Why do we use models in science?

  They help understand difficult concepts.
• What does the big bang theory propose?

  The universe started from a tiny, dense space.
• What is the current understanding of the universe's expansion?

  It started with the big bang and continues today.
• What is the nature of the universe's initial state according to the big bang theory?

  It was unimaginably dense and hot.
• What is the main question regarding the universe's expansion?

  How did a tiny thing expand to a huge universe?
• What is the honest answer to how the universe began?

  We don't know, but have good ideas.
• What is the significance of the big bang theory?

  It explains the origin of the universe's expansion.
• How does the big bang theory relate to the current state of the universe?

  It suggests the universe is still expanding.