Tuesday, January 4, 2011

Solar System: The Planets to Scale: Part II

While planet size is out-of-whack in textbooks, it's nothing compared to the distances between planets.  Most textbook pictures look a little something like my picture above (except, of course, the planets all look much closer in size), the planets are all right next to each other.  The textbooks do it for the same reason that I did: it's the way to make all the planets fit. 

There's so much empty space in space that it's darn near impossible to show students both the planets and their orbits to scale.

But, if you want to give it a shot, pick up your props from last week's solar system and head out for a walk....

Start at the sun and walk 190 feet.  Place the peppercorn (Mercury).

Walk 170 feet.  Place the mini-marshmallow (Venus).

Walk 131 feet.  Place the Gobstopper (Earth).

Walk 263 feet.  Place the split pea (Mars).

Walk 601 yards (about 1/3 mile).  Place the soccer ball (Jupiter).

Walk 1/3 mile.  Place the melon (Saturn).

Walk 1 mile.  Place the baseball (Uranus).

Walk 1 mile. Place the small apple (Neptune).

Walk 1 mile.  Place the sprinkle (Pluto).

You've walked more than 3 1/2 miles from the sun to get to that tiny sprinkle of Pluto.  How much sun do you think Pluto sees?  Not much! 

Given that you probably don't want to walk your students out 3 1/2 miles (and then back 3 1/2 miles), you might want to have them walk the first 190 feet, to get an idea of the distance.  And, then you could determine where each of the other planets would fall, within your school and community.  For example, the Earth is at the cafeteria, or Uranus is at McDonalds. 

It's completely mind-boggling and a lot to think about!


  1. There actually is a simple way for teachers to walk their students across a scale model of the Solar System. You just have to scale it down a lot smaller than you've done. Here is a single photo where both planet sizes & distances are represented accurately:

    Shrink the Sun-Neptune radius down to the length of a football field and the gas giants are about the size of a bb pellet. The terrestrial planets are represented with Bic pens, as their size shrinks down to about the size of the 1mm ball point. At this scale, the Sun is two-thirds the diameter of a golf ball. At the start, the Sun and all 8 planets fit easily within the palm of one hand. Placing the Sun at one goal line, you can then walk down the field to the approximate locations of the planets with Mercury at the 1 yard line, Venus at the 2 yard line, Earth at the 3 yard line, Mars at 5 yards, Jupiter at 17 yards, Saturn at 32 yards, Uranus at 64 yards, and Neptune at the opposite goal line. You could scatter some dust at 9 yards for the Asteroid Belt, along with some dust for the Trojans and such. And then send someone out way past the end goal line to scatter more particles to represent Pluto and the other stuff out there.

    Before leaving the field, it would be good to emphasize the point that all of that empty space you've just walked is only the radius. The full orbit spans the whole diameter which is double the field length. Then look up and down to imagine the emptiness in the sphere above and below you. And then think of how all of this vast bubble of emptiness is the "dense region" within the emptiness of interstellar space.

    Using this method, it would be very easy for all school kids to be taught the accurate scale of the Solar System. It would make for a fun and eye-opening outing. The sports fields are already there for them to play on. Now they can ponder the universe at the same time. And teaching this also make for a great opportunity to teach the vast emptiness that is found within the atom. If the diameter of a large domed stadium represents the orbit of an electron within a hydrogen atom, then the proton nucleus at the center is about the size of a pea. And if you examine the three quarks inside that pea, guess what you find? More emptiness.

    The universe is amazing. We can do a much better job of conveying that to our children.

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