Edwin Hubble's Law Calculator

Hubble's Law Equation:

\[ d = \frac{v}{H_0} \]

Distance (d):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is Edwin Hubble's Law?

Edwin Hubble's Law describes the relationship between the recessional velocity of galaxies and their distance from Earth. It provides the foundation for our understanding of the expanding universe and is a cornerstone of modern cosmology.

2. How Does the Calculator Work?

The calculator uses Hubble's Law equation:

\[ d = \frac{v}{H_0} \]

Where:

\( d \) — Distance in megaparsecs (Mpc)
\( v \) — Recessional velocity in kilometers per second (km/s)
\( H_0 \) — Hubble constant in km/s/Mpc

Explanation: The equation shows that the recessional velocity of a galaxy is directly proportional to its distance from Earth, with the Hubble constant as the proportionality factor.

3. Importance of Hubble's Law

Details: Hubble's Law provides evidence for the expansion of the universe and allows astronomers to estimate distances to faraway galaxies. It also helps determine the age of the universe and supports the Big Bang theory.

4. Using the Calculator

Tips: Enter recessional velocity in km/s and Hubble constant in km/s/Mpc. Both values must be positive numbers greater than zero.

5. Frequently Asked Questions (FAQ)

Q1: What is the current accepted value of the Hubble constant?
A: The value is approximately 70 km/s/Mpc, though measurements range from 67-74 km/s/Mpc depending on the measurement method used.

Q2: How accurate is distance measurement using Hubble's Law?
A: For distant galaxies, Hubble's Law provides reasonable estimates, but local measurements may be affected by peculiar velocities not related to cosmic expansion.

Q3: What is a megaparsec (Mpc)?
A: A megaparsec is a unit of distance equal to approximately 3.26 million light-years or 3.086 × 10¹⁹ kilometers.

Q4: Can Hubble's Law be used for all galaxies?
A: It works best for galaxies beyond our Local Group where the expansion of the universe dominates over local gravitational effects.

Q5: How was Hubble's Law discovered?
A: Edwin Hubble discovered the relationship in 1929 by comparing galaxy distances (from Cepheid variable stars) with their redshifts.