A True Scale Model of the Solar System 

Commercial models, such as this, give a very misleading picture of the relative sizes and distances of objects in our solar system. To get a better feel for the true scale of the solar system, the ASTR 1010 class has constructed such a model, using the Sun in a similar commercial model to set the scale. On this scale, all of the solar system, apart from the Oort cloud (see below), will only just fit on the TTU campus!

You can read about this model below. If you would like to take a tour of this model you can download a guide to help you. (If you would like to create your own model the Exploratorium in San Francisco has a handy on-line calculator.)


Sun (Scale size = 140 mm)
For our campus model the Sun is taken to be the 14 cm (6 in) diameter sphere at the center of the commercial model that can be seen in a display case opposite Room 215 in Bruner Hall. While the commercial model shows all the planets within about 15 inches, a true scale model is very different from this (but we will stay in Bruner Hall for the inner planets!)

Mercury (Scale size = 0.4 mm, Scale Distance = 5.8 m)
Mercury is the closest planet to the Sun, yet on this scale it is a tiny dot on the wall about 19 ft away to the left!

Venus (Scale size = 1.2 mm, Scale Distance = 10.9 m)
Venus is the hottest planet (>800°F on surface) due to a runaway greenhouse effect. You can find it on the wall past Mercury.

Earth & Moon (Scale size = 1.2 mm, Scale Distance = 15 m)
In terms of size Earth and Venus are ‘sisters’. However, Earth’s distance from the Sun allows water to exist in liquid form, which makes a big difference! On this scale the Moon is a 0.3 mm dot about 3.5 cm away from the Earth. Our model Earth and Moon are on a notice board back to the other side of the Sun, past the main entrance.

Mars (Scale size = 0.6 mm, Scale Distance = 23 m)
Mars is only about half the size of the Earth. This smaller size, and increased distance from the Sun mean it has a much thinner atmosphere and is significantly colder than the Earth. Nevertheless there is strong evidence there was once liquid water on its surface. To find Mars in our model, keep going past the Earth.

Asteroid Belt (Scale sizes less than 0.1 mm, Scale Distance = 30 m to 45 m)
Thousands of small rocks in between the orbits of Mars and Jupiter. They would stretch from inside Bruner Hall well into the Library. In our model it is represented by some gains of sand next to the door on the first floor at the east end of the building. Though many think of the Asteroid Belt as being full of tiny rocks, in reality they are an average of a million miles apart, so the dots should be spread all around the Sun at an average of about of 15 cm apart.)

Ceres (Scale size = 0.1 mm, Scale Distance = 40 m)
The largest of the asteroids, Ceres is now classified as a dwarf planet but on our scale it would still be less than 0.1 mm in diameter. To find it look on the window at the east end of the second floor hallway.

To place all the other objects in the solar system at appropriately scaled distances we have to move beyond Bruner Hall!


Jupiter (Scale size = 14 mm, Scale Distance = 78 m)
The largest planet is only about half an inch across on this scale! It is represented by a disk a on the wall opposite the second floor men's bathroom at the west end of Brown Hall. It’s four largest moons, Io, Europa, Ganymede, and Callisto, which are mere specks less than 0.6 mm across, should lie within 18 cm of Jupiter, but in our model are on the floor below it. A couple of these are thought to have liquid water oceans below their icy surfaces!

Saturn (Scale size = 12 mm, Scale Distance = 144 m)
Saturn (without its rings) is only slightly smaller than Jupiter. You can find it in the Volpe library near the elevator that is half way to the back and diagonally to the right of the information desk.

Uranus (Scale size = 5 mm, Scale Distance = 290 m)
Beginning to get really out there now. Uranus is represented by a small bead in Memorial Gym. To find it go in the main entrance and then go down the hallway to the left of the central gym area. It is posted on the wall a few yards down here.

Neptune (Scale size = 5 mm, Scale Distance = 450 m)
Neptune, the furthest major planet from the Sun, is the same size as Uranus but about twice as far away!  In our model it is represented by a bead that is posted on the very right of the front wall of the Baptist College Ministry, just across 7th Street opposite Dunn Hall.

Pluto (Scale size = 0.2 mm, Scale Distance = 590 m)
Today we understand that Pluto is just one of the larger icy objects in what is called the Kuiper Belt, but it still holds some extra fascination because it was classified as a planet for so long. In our model Pluto is a small speck in Foundation Hall, on the right wall just inside the main entrance.

Kuiper Belt (Scale sizes: less than 0.2 mm, Scale Distance = 450 m to 750 m)
This wide belt of icy asteroids surrounds the eight planets, outside the orbit of Neptune. We now know that Pluto is just one of the larger Kuiper Belt objects. The class representation of the Kuiper Belt is a large display under the TV to the left of Room 139 in the STEM Center (Ray Morris Hall).

Oort Cloud
This cloud is thought to be a spherical distribution of icy asteroids stretching almost halfway to the next star. On the scale of the Sun in our model, its extent is so great we can’t fit it on campus, let alone Cookeville, or even Tennessee. In fact it’s represented on a map in the display case next to the Sun in Bruner Hall and stretches hundreds of miles, even on our scale model, from just outside Cookeville all the way to the west coast!

If you are wondering where the next star is, that would be Alpha Centauri, which is about 4.2 light years away. In our model that would put it just over 2,500 miles from Cookeville, for example in Juneau, AK or Quito, Ecuador!