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:

• Background radiation supports the Big Bang theory but doesn't directly address whether the universe will collapse or keep expanding.
• The existence of galaxies outside the Milky Way is a general fact about the universe's structure and not relevant to the expansion - collapse debate.
• If the expansion of the universe is accelerating, it is less likely that gravity will be able to pull galaxies back together (as required for a reverse Big Bang).
• The formation of gas giants in cooler regions of the solar system has nothing to do with the large - scale fate of the universe (expansion or collapse).

Answer:

The expansion of the universe is accelerating.