Question

there is a theory that gravity could pull galaxies back together, causing a reverse big bang. which observation makes this theory less likely than the idea that the universe may continue to expand? ○ background radiation is present. ○ galaxies exist outside of the milky way. ○ the expansion of the universe is accelerating. ○ gas giants form farther from the sun, where temperatures are cooler.

Explanation:

A reverse Big Bang (Big Crunch) relies on gravity slowing and reversing cosmic expansion. An accelerating expansion means the universe is moving apart faster over time, counteracting gravity's pull and making a collapse far less likely. The other options are irrelevant: background radiation confirms the Big Bang, other galaxies just show the universe's scale, and gas giant formation is a solar system-specific process.

Answer:

The expansion of the universe is accelerating.