One of the questions I receive most frequently is this: Since the stars are so distant and their light takes many centuries to reach us, how do we know they still exist?
An excellent question but one that presumes that stars just go out at some point. That’s not true, however.
The hydrogen fusion by which stars shine does end at some point, but that process can take many millennia to occur.
In other words, stars don’t just “go out” … at least not on a human time scale.
Most stars shine for billions of years, and a few centuries or millennia to a star might be equivalent to only a few seconds or minutes to a human.
Wrapping our heads around astronomical concepts often requires us first to grasp the differences between human and cosmic time scales.
Sometimes folks ask if the constellation shapes change over time. Another great question and, again, one that requires an acceptance of human versus cosmic time scales.
I often say that if you’d like to see the constellations that Galileo or Aristotle saw, just go outdoors and look up.
Go back in time much further, however, and that might not be the case. You see, stars are individual suns located at many different distances from us, and most are moving on their own in random directions and speeds of many miles per second.
Since the stars reside trillions of miles away, we’re not able to notice their movements with our eyes alone over relatively short periods (human time scales).
Instead, we perceive them as fixed in the heavens.
If we are patient, however — and by that I mean tens-of-thousands-of-years patient — we’d be able to see reality.
For example, check out the stars of the constellation Scorpius, now appearing in the southern sky just after dark.
Its bright reddish-orange star Antares forms the heart of the great arachnid; above it, you can see the stars representing its claws, and below, its long, curving tail.
Historians believe Scorpius is one of the earliest constellations to have been devised, perhaps first pictured by Euphratean astronomers seven millennia ago as one of the original six zodiacal signs.
While ancient cultures of Persia, Turkey, India and possibly even the Mayans of Mexico saw this star grouping as a scorpion, others did not.
In ancient China, for example, the same stellar figure was considered a major portion of the large and regal figure of the Azure Dragon or Dragon of the East.
And in the South Pacific, Maori legend describes it as the magic fishhook that Maui used to raise the islands of New Zealand from the ocean.
But go back in time much further — back to a time of the Upper Paleolithic era, when humans began drifting from Africa to Asia and Eurasia — and this star grouping would have looked quite different.
Similarly, look forward 500 centuries, and even more changes are in store for Scorpius. Will our ancestors be on Earth at that time to enjoy these changes, or will they be watching them from out there among the stars?
Always fun to ponder while stargazing under a dark summertime sky!
