red shift

• What is red shift?

  It is the stretching of light waves.
• What does the red shift indicate about galaxies?

  They are moving further away from us.
• 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 red shift?

  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?

  Chemicals in the sun's atmosphere absorb them.
• How does the absorption spectra of distant galaxies differ?

  The dark lines are shifted towards red.
• What causes the red shift in light from distant galaxies?

  The stretching of light waves as they travel.
• What does a wavelength shift from 600 nanometers to 650 nanometers indicate?

  The galaxy is moving away from us.
• How do galaxies move away from us according to the video?

  Space between galaxies is expanding.
• How can we visualize the expansion of the universe?

  Using a balloon with markers.
• What happens to the markers on the balloon as it 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 video suggest about the universe's beginning?

  The universe was once tiny and dense.
• What is the generally accepted idea about the universe's expansion?

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

  It was unimaginably dense and hot.
• What continues to happen after the big bang?

  Space itself continues to expand.
• What is the conclusion of the video regarding the discussed topics?

  It aims to clarify complex concepts.