Hubble constant is rate of

Options

A. Reformation in universe
B. Elimination of celestial bodies in black holes
C. Compression in universe
D. Expansion of universe.

Answer

**Step-by-Step Solution:**

1. **Understanding the Hubble Constant**: The Hubble constant is a value that describes the rate of expansion of the universe. It was first calculated by Edwin Hubble in the 1920s.

2. **Defining Expansion**: The term "expansion of the universe" refers to the observation that galaxies are moving away from each other, indicating that the universe itself is growing larger over time.

3. **Rate of Expansion**: The Hubble constant quantifies this expansion. It indicates how fast galaxies are receding from us at different distances. The further away a galaxy is, the faster it appears to be moving away.

4. **Significance of the Hubble Constant**: Understanding the Hubble constant is crucial for cosmology as it helps scientists determine the age of the universe and its rate of expansion, which are essential for studying the universe's evolution.

5. **Conclusion**: Based on the understanding of the Hubble constant, the correct answer to the question "Hubble constant is a rate of" is the "expansion of the universe."

**Final Answer**: The Hubble constant is a rate of expansion of the universe.

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