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Our Changing Big Dipper

By Dennis Mammana- Like you, I’ve lived and worked on this planet for many years and, in that time, I’ve learned a valuable lesson: Whatever is temporary is permanent, and whatever is permanent is temporary.

This applies everywhere — buildings, governments, relationships. Things we’re convinced are everlasting are almost always destined to change. And those that we’re told will be only temporary — taxes, detours, visits from in-laws — well, they often turn out to be permanent!

Even the heavens, which we humans perceive as eternal and unchanging, are only temporary. While we often refer to the stars and constellations as being fixed — especially when we watch the moon and planets drift gracefully in front of them — they are actually moving in seemingly random directions at speeds of many miles per second.

But since the stars reside trillions of miles away, we’re not able to notice their movements without sophisticated instruments or waiting inconceivably long periods of time. So, it’s only natural that we perceive them as fixed.
If we are patient, however, we can see reality.

Take, for example, the stars of the Big Dipper. To most of us in the Northern Hemisphere, this great celestial icon is one of the first star groupings we learn to recognize. Every scout has used it to locate the North Star and find direction during the night.

But seeing this movement is another matter altogether. If we could accelerate time and watch this star grouping for tens of thousands of years, we would begin to see how its stars move through space and the shape we know as the Big Dipper would change.

A hundred thousand years ago, the first Homo sapiens in the Middle East might have recognized this stellar collection as a celestial fishhook rather than a dipper. Our descendants a hundred millennia in the future will also see the shape of a dipper — but one that is distorted and reversed from what we see today.

So, the next time you think about heading outdoors to enjoy the stars and constellations, don’t put it off too long. Remember: Whatever is temporary is permanent, and whatever is permanent is temporary!

Its shape has been represented by various cultures throughout history as a wagon, plow, bear followed by three warriors and, in the Chinese culture, the government itself. Its “drinking gourd” shape even served in song to inspire pre-Civil War slaves to flee northward to freedom.

We’ve come to recognize the seven stars of its bowl and long, curving handle to be about as permanent a sight as there is. But what we see as the Big Dipper is not real. It’s not a solid structure but purely an optical illusion that occurs because of where we live in our galactic neighborhood. If we could fly freely through space and travel to the other side of those stars, we would discover that our perception of the Dipper would change along the way.

The dipper shape is fluid over time as well. Its five central stars are stellar siblings: They were born from the same interstellar cloud some 500 million years ago and still travel together at
remarkable speeds.

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