1. What is Hubble's Law?

Hubble's Law describes the relationship between the distance to a galaxy and its redshift. It's a fundamental principle in cosmology that provides evidence for the expansion of the universe.

2. How Does the Calculator Work?

The calculator uses Hubble's Law equation:

Where:

• \( d \) — Distance in megaparsecs (Mpc)
• \( z \) — Redshift (dimensionless)
• \( c \) — Speed of light (3 × 10⁵ km/s)
• \( H_0 \) — Hubble constant (km/s/Mpc)

Explanation: The equation shows that the recessional velocity of a galaxy (indicated by its redshift) is proportional to its distance from us.

3. Importance of Hubble Distance

Details: Hubble distances are crucial for mapping the large-scale structure of the universe, determining cosmic expansion rates, and estimating the age of the universe.

4. Using the Calculator

Tips: Enter redshift (z) as a dimensionless value (e.g., 0.05 for 5% redshift). The default Hubble constant is 70 km/s/Mpc but can be adjusted based on current measurements.

5. Frequently Asked Questions (FAQ)

Q1: How accurate is Hubble's Law for distance measurement?
A: It works well for distant galaxies (z > 0.01) but has limitations for nearby galaxies where peculiar velocities dominate.

Q2: What value should I use for H₀?
A: Current estimates range from 67-74 km/s/Mpc. The default 70 km/s/Mpc is a commonly used intermediate value.

Q3: Does this work for all redshifts?
A: This simple form is valid for z < 0.1. For higher redshifts, relativistic corrections are needed.

Q4: Why is the speed of light in units of km/s?
A: We use 3 × 10⁵ km/s to match the units of the Hubble constant (km/s/Mpc).

Q5: How does this relate to the age of the universe?
A: The inverse of the Hubble constant gives a rough estimate of the universe's age (1/H₀ ≈ 14 billion years for H₀ = 70 km/s/Mpc).