Final answer:
The belief that all galaxies formed at about the same time and have changed little since then is false. Galaxies evolve and change significantly, with observations showing that distant, younger galaxies are smaller, more irregular, and have higher rates of star formation compared to galaxies in the current universe.
Step-by-step explanation:
The statement that “All galaxies originally formed at about the same time, long ago, when the universe was young” is false. Early observations suggested that galaxies might have appeared fully formed, leading to the belief that they changed very slowly over time. However, more recent observations demonstrate that galaxies have actually evolved significantly. When we look at distant galaxies, we are looking back in time, and we can see that younger galaxies tend to be smaller, have more irregular shapes, and have higher rates of star formation than the galaxies we see nearby today. Over billions of years, galaxies have undergone mergers and have grown in size, leading to the diverse variety of galaxies we can observe presently. Galaxy evolution is a dynamic and ongoing process, rather than a singular event.
Understanding the color of a galaxy helps us determine the age of its stars, with younger, bluer galaxies hosting more hot, massive young stars, and older, reddish galaxies hosting older stars. The evidence of galaxy mergers, such as small galaxies merging to form larger ones, and the formation of clusters and superclusters, counters the early hypothesis of static galaxies. Indeed, the universe and its galaxies have undergone significant changes, such as star formation and galactic assembly, throughout cosmic history.