A Vast and awesome Universe – Understanding cosmic distance through analogy

When a budding interest in astronomy is pursued with even a cursory investigation into the nature of our cosmos, one quickly comes to the realization that the human mind cannot fully embrace the awesome extent of it all—the unfathomable distances and mind-bending time scales—the incomprehensible vastness of the gulf of space. And although even our imagination may fall short, it is precisely the reality of this vastness and its incomprehensibility that, to me, is the grandest playground of the imagination.

Consider for a moment the distance to our nearest star. Alpha Centauri, I can tell you, is 4 ¼ light years (ly) away. And at the speed of 300,000 kilometres per second (km/sec), the distance light travels in 4 ¼ years makes Alpha Centauri very far away indeed. I’m not sure it helps much to state that that equates to 41.5-trillion kilometres, or 277,600 astronomical units (AU: the average distance between the Earth and the Sun). These unfathomable distances, with numbers so grand, are just too much for the mind to grasp and are perhaps better understood through analogy.

So let’s just build such an analogy, with a scaled-down Solar System, and begin by shrinking our Sun down to the size of a baseball, the kind that the Toronto Blue Jays use. And to keep it relevant, we’ll place our baseball-sized Sun right in the very center of the intersection of Second and Main, in downtown Whitehorse, and lay out some of our planets to scale, by heading south down Second Ave towards the SS Klondike.

Earth (now about the size of the ball in the end of a ballpoint pen), along with Mercury and Venus, would still be within the confines of the intersection, not even touching the first crosswalk. Jupiter, the largest planet of our Solar System (now reduced to the size of a pea), would be just down the first block of Second Avenue, not quite to the alleyway behind Starbucks. Saturn barely makes it to the far side of the intersection of Elliott and Second, just one block from Main Street. Eventually, lonely little Pluto, so shamelessly cast out of the family of planets and demoted to “dwarf planet” status (and now barely visible in our model Solar System), would be just to the far side of the intersection of Hanson and Second, near the Deli. After that, although there are the thinly dispersed icy bodies of the Kuiper Belt and the Oort Cloud, from whence the comets come, there is a tremendous gulf of space before you come to even our nearest neighbouring star.

Alpha Centauri is roughly equivalent in size to our Sun, so it too would be baseball-sized in our scaled-down analogy. But to place it to scale in our model, you’ll have to travel substantially farther south than Second Avenue goes. Or even the Alaska Highway, for that matter. In fact, you’d better pack your passport, for you will be placing our baseball-sized Alpha Centauri in the town square of the small hamlet of Redmond, in central Oregon, more than 2,100 km away! A tremendous gulf of space indeed!

And to tickle the imagination just a little further, consider Voyager 1 and 2, those amazing little spacecraft that celebrated their 40th anniversary in space, just last year. Voyager 1, whizzing away from us at 17 km/sec, is the farthest human-made object from our planet and is still faithfully sending back data on the cosmic rays and charged particles of interstellar space. These bottles in the cosmic ocean, with their gold records of sounds and descriptions of us and our planet, are destined to drift off into the spiral arms of our galaxy for the rest of the age of the Universe.

However, even after 41 years and 21-billion kilometres, Voyager 1 would still have an enormous distance to travel if it was voyaging to Alpha Centauri. Probably the size of a molecule in our model now, Voyager 1 wouldn’t even be to the SS Klondike, yet, on its way to Central Oregon. In fact, even at that breakneck speed of 17 km/sec, it would take our stalwart little craft another 90,000 years to complete the journey! And Alpha Centauri is just the nearest of the hundreds of billions of other stars in our Milky Way galaxy, the first of hundreds of billions of other galaxies.The Universe, this grand playground of the imagination, is an awesomely huge place. My hope with this column is to encourage all budding astronomical contemplations of our Cosmos by highlighting the fascinating stargazing features of our un-light-polluted northern skies. Each article will feature a particular astronomical object that will require nothing more than the naked eye or binoculars to see.

So, till next issue, keep looking up and let your imagination run wild. The Universe awaits with awe!

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