Why is the universe expanding?
Show answer & explanation
Answer: Space itself is stretching
Space itself is stretching ✓ — Correct! The universe expands because space itself stretches—not galaxies moving through space. Discovered by Hubble (1929): galaxies recede with speeds proportional to distance (Hubble's Law). Evidence: cosmological redshift. Driven by Big Bang initial expansion and dark energy (accelerating expansion). Space creates itself as it expands. Mind-bending concept—expansion of spacetime fabric!
Gravity weakens over time — Wrong. Gravity's strength doesn't change. Expansion occurs despite gravity trying to pull everything together. Dark energy drives accelerating expansion.
Dark matter repels galaxies — Wrong. Dark matter attracts gravitationally like normal matter. Dark energy (not dark matter) drives accelerating expansion—unknown force.
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