Space and relativity

• What is a light year?

  The distance travelled by light in one year
• How is a light year defined?

  Distance travelled by electromagnetic wave in a year
• How can distances in the sky be measured using parallax?

  By measuring angles at different times
• What is redshift?

  Apparent increase in wavelength of light
• What does redshift from distant galaxies suggest?

  Distant galaxies are moving away from us
• What does a greater redshift indicate about a galaxy?

  The galaxy is moving away faster
• What theory does the redshift of distant galaxies support?

  The Big Bang Theory
• What is Hubble’s Law?

  Recessional velocity is proportional to distance
• What relationship is used to calculate the proportional change in wavelength?

  $\frac{\Delta \lambda}{\lambda} =$$\frac{v}{c}$
• What does CMBR stand for?

  Cosmic Microwave Background Radiation
• What does CMBR provide evidence for?

  The Big Bang Theory
• What was Einstein’s First Postulate for his Theory of Special Relativity?

  Physics laws are the same for all observers
• Where is CMBR believed to originate from?

  Gamma rays from the Big Bang
• What happens to the wavelength of radiation from CMBR as the universe expands?

  The wavelength has been stretched
• What was Einstein’s Second Postulate for his Theory of Special Relativity?

  The speed of light is a universal constant
• What is time dilation?

  Different observers record different event times
• What unit is used to measure large distances in space?

  Light years
• What is one light year defined as?

  The distance light travels in one year
• How many meters are in one light year?

  $9.461 \times 10^{15} \text{ m}$
• How does radar measure distances in the solar system?

  A pulse is transmitted and reflected back
• What formula is used to calculate the distance travelled by a radar pulse?

  $s =$$ct$
• Why is the distance calculated from radar pulses halved?

  Because the pulse travels to and from the object
• How can velocity be calculated using radar measurements?

  Distance moved divided by time between readings
• What method can be used to measure large distances using angles?

  Parallax
• How does parallax work to measure distances?

  By measuring angles at different times of year
• What theorem is used in parallax to calculate distance?

  Pythagoras’ Theorem
• What are standard candles used for in astronomy?

  Estimating distances using star brightness
• How do standard candles estimate distances?

  By comparing apparent and absolute brightness
• What does red shift indicate about a galaxy's movement?

  It is moving away from the observer
• What does the Doppler effect describe?

  The change in wavelength due to motion
• How does red shift provide evidence for the Big Bang Theory?

  It shows galaxies are moving away from us
• What does Hubble's Law state about distant galaxies?

  They have a higher recessional velocity
• What is the Hubble constant's unit?

  1/time
• What is Cosmic Microwave Background Radiation evidence of?

  The Big Bang
• What was believed to be the origin of Cosmic Microwave Background Radiation?

  Gamma rays from the Big Bang
• How did Cosmic Microwave Background Radiation change as the universe expanded?

  Its frequency decreased to form microwaves
• What do space-time diagrams plot against each other?

  Time in years against distance in light years
• What angle does a ray of light make in space-time diagrams?

  45 degrees
• What does Einstein's First Postulate state about physics?

  It works the same for all observers
• What does Einstein's Second Postulate state about the speed of light?

  It is a universal constant