The Universe

• What are absorption spectra

  Absorptions lines arise from gas atoms in stars atmosphere and absorbing specific wavelengths of visible light.

  Wavelengths absorbed are specific to elements present in star
• What happens when substances are very hot?

  They emit light
• How can light from hot gases be viewed?

  Through a diffraction grating
• What type of spectrum do hot gases emit?

  Specific frequencies or wavelengths
• How can we identify the composition of gas in a star?

  By matching frequencies to elements
• What is a line emission spectrum?

  Light emitted by an element in hot gas
• What does a hot gas cloud release?

  A series of light frequencies
• How do line emission spectra act for elements?

  Like a chemical fingerprint
• What happens when a gas cools?

  It absorbs the same frequencies of light
• What appears as dark lines in an absorption spectrum?

  Absorbed frequencies of light
• How can we determine elements in a cool gas?

  By observing the absorption spectrum
• Who invented the spectroscope?

  Joseph von Fraunhofer
• What did scientists use absorption spectra for in the 19th century?

  To identify elements in Earth's atmosphere
• What happens to the wavelength of sound when the source moves towards an observer?

  It is compressed
• What is the effect on pitch when a sound source moves away?

  Pitch decreases
• What is the Doppler effect?

  Change in wavelength due to movement
• What happens to light emitted by a planet moving away from an observer?

  It experiences red shift
• What does red shift indicate about a planet's movement?

  It is moving away from the observer
• Who first hypothesized the cosmological red shift?

  Edward Hubble
• What does blue shift indicate about a planet's movement?

  It is moving towards the observer
• What did Hubble observe about galaxies' absorption spectra?

  They displayed red shifted patterns
• What does Hubble's observation suggest about galaxies?

  They are moving away from the Milky Way
• What does Hubble's Law correlate?

  Distance and degree of red shift
• What is Hubble's constant?

  The gradient of the line in Hubble's plot
• How can Hubble's constant be used?

  To estimate the age of the universe
• What is the Cosmological red shift

  Wavelengths of absorption lines are increased and this effect increases with distance.

  Light from further galaxies show most red shift due to having it travelled for greater amount of time, increasing wavelength
• What was detected for the first time in 1964?

  Microwave radiation as part of CMBR
• What type of radiation was initially released during the Big Bang?

  High energy, short wavelength gamma radiation
• What happens to gamma waves as the universe expands?

  They red-shift into microwaves
• What is CMBR

  At time of Big bang high energy short wavelength gamma rays were produced.

  Over time as space expanded gamma rays also stretched forming microwaves.
• What is Big Band Theory

  theory that all galaxies originated from a single point

  if expansion of the universe was reversed everything would revert back to one single point