Hubble's Law

• What does Hubble's Law state?

  The recessional velocity of a galaxy is proportional to its distance from Earth

  
• How can Hubble's Law be expressed mathematically?

  v = Hd
• What does 'v' represent in Hubble's Law?

  Recessional velocity of an object

  
• What does 'H' represent in Hubble's Law?

  Hubble constant
• What does 'd' represent in Hubble's Law?

  Distance between the object and the Earth
• What does Hubble's Law indicate about distant stars?

  The further away a star is, the faster it moves away
• What does Hubble's Law indicate about nearby stars?

  The closer a star is, the slower it moves away
• What is a key aspect of Hubble's Law regarding galaxies?

  The furthest galaxies appear to move away the fastest

  
• What is the formula for the Hubble constant?

  H = v/d
• How is the Hubble constant estimated?

  Using data from thousands of galaxies

  
• What is the current best estimate of the Hubble constant?

  H = 67.4 ± 0.5 km s⁻¹ Mpc⁻¹
• Why is the value of the Hubble constant constantly under review?

  As more data is collected
• What is the significance of Hubble's Law in estimating the age of the Universe?

  • It estimates the time since expansion began
  • Helps calculate the age of the Universe
• How can we calculate the time taken to reach a distant object?

  Using distance and recessional speed
• How do you calculate the Hubble constant from the graph?

  Gradient of the speed-distance graph

  
• What assumptions are made when using Hubble's Law to estimate the age of the Universe?

  • All points in the Universe were initially together
  • The recessional speed of a galaxy is constant

  
• How is time related to distance and speed in the context of Hubble's Law?

  time = distance/speed

  
• How is time expressed in relation to the Hubble equation?

  time = 1/H
• What do astronomers believe about the age of the Universe?

  It has been expanding for around 13.7 billion years
• How do you calculate the age of the Universe using the Hubble constant?

  t = 1/H
• What was the best estimate for the Hubble constant in 2020?

  67.4 km s⁻¹ Mpc⁻¹
• How do you convert the Hubble constant from km s⁻¹ Mpc⁻¹ to m s⁻¹ Mpc⁻¹?

  Multiply by 1000
• What is the conversion factor for 1 Mpc to meters?

  1 Mpc = 3.1 × 10²² m
• How do you convert the Hubble constant to seconds?

  H = 6.74 × 10⁴ m s⁻¹ Mpc⁻¹
• What is the calculated age of the Universe based on the Hubble constant?

  Age = 14.6 billion years
• What are the steps to calculate the age of the Universe using the Hubble constant?

  1. List known quantities
  2. Convert units as necessary
  3. Calculate Hubble constant in appropriate units
  4. Use t = 1/H to find age