Hubble’s law

Definition

Hubble's law states that the velocity at which a galaxy moves away from us is directly proportional to its distance from us. This relationship supports the concept of an expanding universe.

5 Must Know Facts For Your Next Test

1. Hubble's law was formulated by Edwin Hubble in 1929.
2. The law is often expressed with the equation v = H₀d, where v is the galaxy's recessional velocity, H₀ is the Hubble constant, and d is the distance to the galaxy.
3. Hubble's discovery provided strong evidence for the Big Bang theory.
4. The value of the Hubble constant (H₀) helps determine the rate of expansion of the universe.
5. Observations of redshift in light from distant galaxies were key to establishing Hubble’s law.

Review Questions

• What does Hubble's law imply about the movement of galaxies?
• How does Hubble’s law support the concept of an expanding universe?
• What role does redshift play in confirming Hubble’s law?

Related terms

Redshift:

The phenomenon where light from an object moving away from an observer is increased in wavelength, or shifted to the red end of the spectrum.

Big Bang Theory:

The leading explanation for how the universe began, proposing it started from a singularity approximately 13.8 billion years ago and has been expanding ever since.

Hubble Constant (H₀): A measure of the rate at which the universe is expanding, expressed in kilometers per second per megaparsec (km/s/Mpc).