1. What is Hubble's Law?

Hubble's Law describes the relationship between the distance to a galaxy and its recessional velocity due to the expansion of the universe. It was first formulated by Edwin Hubble in 1929.

2. How Does the Calculator Work?

The calculator uses Hubble's Law equation:

Where:

• \( v \) — Recessional velocity (km/s)
• \( H_0 \) — Hubble constant (km/s/Mpc)
• \( d \) — Distance to galaxy (Mpc)

Explanation: The farther a galaxy is from us, the faster it appears to be moving away due to the expansion of space.

3. Importance of Hubble's Law

Details: Hubble's Law provides evidence for the expansion of the universe and is fundamental to modern cosmology. The Hubble constant helps estimate the age of the universe.

4. Using the Calculator

Tips: Enter the Hubble constant (typically around 70 km/s/Mpc) and the distance to the galaxy in megaparsecs (Mpc). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is the current best estimate for H₀?
A: Current estimates range from 67-74 km/s/Mpc, with tension between different measurement methods.

Q2: Why are the units km/s/Mpc?
A: This means for every megaparsec of distance, the velocity increases by the Hubble constant value in km/s.

Q3: Does this work for all distances?
A: For very large distances (>1000 Mpc), relativistic effects become significant and the simple linear relation breaks down.

Q4: What is a megaparsec?
A: 1 Mpc = 3.26 million light-years = 3.086 × 10¹⁹ km.

Q5: Can this be used to calculate the age of the universe?
A: The Hubble time (1/H₀) gives a rough estimate, but the actual age depends on the cosmological model and composition of the universe.