Solar System Walk
The purpose of this activity is to get a sense of the size and scale of the objects in the solar system by walking through a scale model along the Burke-Gilman trail.

Audience: This activity is suitable for adults, college age students and grade school kids. Be aware that older adults and handicapped people might have a hard time walking the whole way. Very small children will not understand where everything past Jupiter is, and won't understand the "point" of the exercise---their abstract thinking skills aren't good enough to picture the solar system in this way.

  1. Begin at the "Right Lane Must Turn Right" sign facing the Burke-Gilman trail on the corner of 15th and Pacific. The "Right Lane Must Turn Right" sign is 2 feet across. This sign represents the Sun, and the rest of the solar system is represented to this scale.
  2. Mercury: Walk east on the Burke-Gilman trail towards the UW Medical Center. Just in front of the stairs leading up to the teaching building is Mercury. On this scale, Mercury is about 3 mm in diameter.
  3. Venus: Across from the doors underneath the sundial is Venus, about 6 mm in diameter.
  4. Earth: Just beyond the edge of the teaching wing, before the light post on the opposite side of the Burke-Gilman trail. Look back at the "Right Lane Must Turn Right" sign. It should be about 0.5 degrees "on the sky". The Earth is just over 6 mm in diameter. You may like to point out that this is 1 AU from the Sun, and light takes about 8 minutes to get here from the Sun.
  5. Moon: The moon is about 17 cm from the Earth on this scale.
  6. Mars: Across from the Kincaid Hall loading dock doors, and just before the first Medical Center bridge is the planet Mars. Mars is about 3.5 mm in diameter.
  7. Asteroid Belt: You have a long-ish walk to Jupiter, and it's appropriate to fill the time by mentioning the Asteroid belt. The asteroids are too small to even represent on this scale.
  8. Jupiter: By the ramp off to the left of the Burke-Gilman trail, just past the second Medical Center bridge. Jupiter is about 6.2 cm in diameter. From here, go onto the bridge and point things out. It is too far to walk... Jupiter is five AU from the Sun.
  9. Saturn: Saturn is located at the second set of traffic lights as seen looking East from the second Medical Center bridge. The lights are usually blinking. Saturn is about 5.2 cm in diameter. Saturn is about 10 AU from the Sun.
  10. Uranus: Uranus is located at 45th and 15th streets, in the University Village. Uranus is about 2.2 cm in diameter.
  11. Neptune: Neptune is out in Gasworks Park, or Ravenna Park. On this scale, Neptune is about 2.1 cm in diameter.
  12. Pluto: Pluto's orbit is just at the bottom of the Fremont hill, or just at the near edge of Greenlake. Pluto is about 1.2 mm in diameter.
The fastest man-made objects are the Voyager spacecraft. They now cover about 2 feet per day on this scale, or 3.3 AU per year. (35,000 mph, 60,000 km/hr)

Alpha Centauri: Alpha Centauri would be another "Right Lane Must Turn Right" sign at the southern tip of Africa. Almost on the opposite side of the Earth. It is good not to tell people this until they've had a chance to guess. Nearly always, they dramatically underestimate the distance...