Sparse Space

If you go outside on a clear night in the country, you can see as many as 3000 stars with the naked eye. The sky seems filled with stars. Look at a photo of a distant galaxy taken by the orbiting Hubble Telescope and you see millions of stars and maybe several distant background galaxies. Space seems so full of planets, stars, and galaxies; and yet it’s vastly empty.

It’s hard to wrap your head around just how sparse space is, or just how far it is between the heavenly bodies we see out there. I’ve often tried to grasp the profound emptiness of it all, or to comprehend just how isolated our little planet is in this cosmic void, but it’s a very big stretch of imagination.

So here’s a way to get a feel for the barrenness of space—putting it in terms of distances we can more easily get a feel for. Let’s look first at our solar system. Our sun dominates it; over 99% of the mass of our solar system resides in the sun. Eight planets, a few proto planets (Pluto was recently designated as one of them), and countless asteroids… all orbit our sun.

To reduce our solar system to a more understandable scale, imagine the sun to be the size of a basketball. Place it on the goal line of a football field. To that scale, our Earth is the size of a fat grape seed, out at the 10-yard line… a wee grape seed revolving out there about 30 feet away. Mars is half that grape seed size, sitting out on the 15-yard line. Jupiter is the size of a walnut at midfield… a walnut out there 150 feet away! Let’s round out our solar system: Pluto is a tiny dot out there about 3 ½ football fields away. Thus, to this scale (the sun the size of a basketball), our solar system has a diameter of about seven football fields.

To consider celestial bodies beyond our solar system, we need to make the scale even smaller. Collapse those seven football fields down to a basketball, and then place that basketball-size solar system on the goal line again. Where’s the nearest star, Alpha Centauri? It’s five miles away. Nothing of any substance exists around our basketball-sized solar system, until you get out there five miles. That’s a pretty empty “local” stellar neighborhood!

Our solar system sits out near the edge of the Milky Way Galaxy. So again, to this second scale, the center of our galaxy is 4000 miles away. That’s about the distance from Washington, D.C. to the Amazon. Let’s go one more: the nearest galaxy to us is Andromeda. By this scale, that closest galaxy (to our basketball-size solar system) is 360,000 miles away—or half again the distance to the moon. Pretty sparse territory.

One often hears talk about humans soon traveling by space ship to the stars. On old Star Trek episodes you can watch the USS Enterprise zip from one star system to another in a few hours. The reality of it is that these distances are far greater than we can imagine. Planet Earth is like a vanishingly small speck of dust on a vast ocean. Even though the universe has uncountable stars and planets, we’re pretty much alone. Maybe we’d better think of taking better care of our home—it is all we’ve got for the foreseeable future, until the far distant day when we just might span those incredible distances.