curiositykillstime

[curiositykillstime]

How big is the solar system?

A NASA spacecraft is right now gunning through the outer regions of the solar system, toward a little-known world beyond Pluto’s orbit. Ultima Thule will become the farthest object humanity has ever seen up close when New Horizon photographs it next year.

The oddly shaped rocky object — or is it two smaller ones orbiting each other? — lies 6 billion kilometers from the Sun. Yes, 6 billion. Just take a moment and try to grasp how far that is. If you’re brain is short-circuiting, you’re not alone. Astronomy, with all its big, scary numbers, can sometimes be hard to wrap my mind around unless I create a familiar context for it.

A quick, easy way to bring to life the solar system, in all its wondrous vastness, is to recreate a small model in a backyard or park, using only a long string and a ruler. A friend and I did this. It took minutes and the result was satisfying. The only prep work was to list the objects in the solar system and their average distances from the Sun, then convert those numbers into smaller denominations, like meters and centimeters. You’ll notice in the chart below that instead of kilometers, I used something called an astronomical unit (AU), which is equal to the distance of the Earth to the Sun (easier than saying 149,597,870 km). The scale of our model is set so that every meter represents an AU. Confusing? All you need to get started is the numbers in italics.

Distance from the Sun

Mercury .4 AU (40 centimeters)

Venus .7 AU (70 cm)

Earth 1 AU (1 meter)

Mars 1.5 AU (1 m, 50 cm)

Jupiter 5.2 AU (5 m, 20 cm)

Saturn 9.5 AU (9 m, 5 cm)

Uranus 19.2 AU (19 m, 20 cm)

Neptune 30 AU (30 m)

Pluto 39.3 AU (39 m, 30 cm)

Ultima Thule 42.4 AU (42 m, 4 cm)

Now it’s time to go outside and create your miniature solar system. Find a place that’s at least 43 meters long. At one end, tie the string to something sturdy, like a tree, fence post, or chair leg. Then get out your ruler and begin plotting out your planets. We tied knots in the string to mark each position, but if you want something easier to see, use colorful ribbon or anything else lying around your home.

Every brain works in its own special way. Your takeaway may be different than mine. Still, here are the impressions I had after seeing the solar system laid out before my eyes. First, there is something moving about standing, with the string in hand, out near Pluto, and straining to see the tiny knot representing our far-off home, Earth. I got a new sense of the remoteness of space and the ingenuity required to explore it. What also struck me was how close the four inner planets are compared to the rest of the objects in the solar system. Past Jupiter, the distances between places really expand exponentially. It’s remarkable how such vast, enormous, and independent worlds are held together by the glue of the Sun’s gravity, all part of the same cosmic family.