Final answer:
Ignoring dark energy, evidence still supports the expansion of the universe indefinitely, with galaxies drifting apart and the universe becoming colder and darker over time.
Step-by-step explanation:
Even if we ignore the phenomenon of dark energy, the evidence suggests that the universe will continue to expand forever. Observations indicate that, while dark energy contributes to the acceleration of this expansion, the universe was already on a trajectory toward perpetual expansion regardless of its presence. If we overlook dark energy, the expectation does not change; the universe will keep on expanding, causing galaxies to spread farther apart over time, leading to a colder, darker universe.
It is important to note that the discovery of dark energy, which is understood to cause the rate of the universe's expansion to speed up, has further enforced this scenario. This acceleration will likely sustain into the indefinite future. Without a substantial force to counteract this expansion, such as a major increase in the density and gravitational pull of matter within the universe, the expansion will not cease. Thus, theories like the 'big crunch,' where the universe eventually collapses back on itself, appear less likely based on current scientific evidence.