They never knew what it was that suddenly ended their lives and destroyed their galaxy.
Long before the end, they had explored their own solar system, detected extrasolar planets, and measured the distances to nearby galaxies. However, their ideas about the universe ended at the frontiers of an expanding bubble and they believed that time began with a "Big Bang".
The ancients had viewed the universe was geocentric: the world was flat; after setting in the West, the sun somehow made its way to the East, just in time to rise each morning; most of those points of light in the night sky were on the inside of a great bowl that arced above it all. There were a few exceptions: the moon, of course, an occasional comet, plus a handful of wandering stars which many believed were gods.
Long ago, they had realized that the land wasn't as flat as it appeared, and that all of the continents, and even the vast seas, were merely floating on the crust of a huge sphere -- a globe that orbited the sun (not vice versa), providing light and heat to one side at a time. Most of the stars visible in the nighttime sky were really other suns, but some were wandering planets, nearby but farther away than the moon. After optical viewing tubes and other devices were invented, they discovered that some of the planets had their own moons,
Eventually, they calculated that, while their planet revolved around the sun after a few hundred daily rotations, their entire solar system (as well as nearby suns) was located in one of the arms of a vast galactic spiral, which rotated about its center every quarter-billion years.
Only in the past century or so was it discovered that some of the so-called "stars" in the skies were in fact other galaxies, just like theirs. They named the nearest one "Andromeda", but their own galaxy never had a name. Some called it "Milky Way" because the other stars in the main disk appeared as a milky band across the sky, but most of them associated that name with a candy bar.
Altho some observers and scientists franticly searched for invisible "dark matter" and while others combed the incoming radio waves to find evidence of intelligent life in the cosmos, most of the visible objects were known and had been measured, as were most of the others that were detectable. To them, nothing existed beyond the boundaries of the "Big Bang" at the beginning of time.
Suddenly, without any warning, their entire known universe was totally destroyed by events far beyond their own imagination.
Jove Chronson stood there, with one bare foot upon the rim, staring fascinatedly at the swirling of the cigarette ash he had flicked into the bowl after finishing his business.
He wondered, "was it Coriolis force, or merely the trickle from the tank, that caused the ash to form such a beautiful, rotating spiral?" Most of the ash was contained in a central pinwheel on the yellowish surface, but some smaller swirls bobbed nearby and there were even a few submerged clumps lingering beneath. Inhaling, he tried to imagine how those outliers might look if he was a mere microbe, crawling on the surface of one of the particles in the swirling display.
Resting his hand on the silver handle, he took one last puff, then dropped the butt into the middle of largest swirl as he simultaneously pulled down to flush.
Bruce Alan Martin
The spiral of ash seemed to revolve every few seconds, while our own spiral galaxy took over 250 million years to revolve about its center. He calculated that, since he had been staring at the swirling spiral for a few minutes, now, that would be about 13 billion years -- if he lived on a planet orbiting a star within such a galaxy.
Looking out the window, into the clear midnite sky, Jove noticed about the milky band of stars that crossed it, wondering, again idly, how our unnamed sun would look from one of those other stars, and how our galaxy might look from the edges of the universe.