Final answer:
Based on star counts 100 years ago, most astronomers thought that the universe of galaxies was a mostly peaceful place.
Step-by-step explanation:
This understanding came from the premise that galaxies had formed billions of years ago and slowly evolved as their stars developed, aged, and ceased to exist. This perception was largely due to the limitation in detecting changes in star positions with the n`aked eye within a human lifetime, as well as the overall tranquil appearance of the cosmos with only about 9000 stars visible without the aid of telescopic equipment.
Astronomers of that era lacked the advanced technology that later allowed for more precise measurements and cataloging of star positions. For instance, space missions have produced catalogs with very high precision, like measuring positions of stars to an accuracy of one-thousandth of an arcsecond. These developments have led to better parallax measurements and an understanding that the universe is much more dynamic than previously thought.