Hubble's Law Calculator Manual

Hubble's Law Equation:

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

Distance (d):

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1. What is Hubble's Law?

Hubble's Law describes the relationship between the recession velocity of galaxies and their distance from Earth. It is 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:

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

Where:

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

Explanation: The equation shows that the velocity at which a galaxy is receding from us is directly proportional to its distance.

3. Importance of Hubble's Law

Details: Hubble's Law is crucial for determining distances to faraway galaxies, estimating the age of the universe, and providing key evidence for the Big Bang theory and the expanding universe model.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: What is the current accepted value of H₀?
A: The Hubble constant is approximately 70 km/s/Mpc, though precise measurements range from 67-74 km/s/Mpc depending on the measurement method.

Q2: Why are distances measured in megaparsecs?
A: Megaparsecs (Mpc) are used in cosmology because they provide convenient units for expressing the vast distances between galaxies.

Q3: Does Hubble's Law work for all galaxies?
A: Hubble's Law works best for distant galaxies. For nearby galaxies, local gravitational interactions can affect their motion relative to the Hubble flow.

Q4: What is redshift in relation to Hubble's Law?
A: Redshift is the observed increase in wavelength of light from distant galaxies, which is used to calculate their recession velocity.

Q5: How accurate is distance calculation using Hubble's Law?
A: Accuracy depends on the precision of H₀ measurement and proper accounting for local motion effects. It's most reliable for galaxies beyond our Local Group.