Why is the universe expanding?
Show answer & explanation
Answer: Space itself is stretching
Dark matter repels galaxies — Wrong. Dark matter attracts gravitationally just like normal matter. It is dark energy, not dark matter, that drives the accelerating expansion.
Gravity weakens over time — Wrong. Gravity's strength does not change over time. Expansion happens despite gravity trying to pull everything together, and dark energy drives the accelerating expansion.
Space itself is stretching ✓ — Correct! The universe expands because space itself stretches, not because galaxies move through space. Hubble discovered in 1929 that galaxies recede at speeds proportional to their distance, which is Hubble's Law. The evidence is cosmological redshift. The expansion is driven by the initial Big Bang and by dark energy, which makes it accelerate.
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