# Labs from YSI 94 : Model of the Solar System.

Dr. Heidi Newberg
CARA Yerkes Summer Institute, August 1994

Below is both the lab for the students and a Teacher's Guide.

Our project is to create a scale model of the Solar System as it is now (the model will change as the planets move around the Sun). We will make a 10,000,000,000:1 model of the Solar System. This means that the distances in the model will be 10,000,000,000 times smaller than they are in the real Solar System. This scale was chosen so that the model can be constructed on the Yerkes grounds.

There are three steps to follow for each planet (plus the Sun):

1. Calculate the size of the planet in our model by dividing the planet's diameter by 10,000,000,000. Then, find something about that size to use for the planet.
2. Calculate the distance the planet is away from the Sun by dividing the Sun-planet distance by 10,000,000,000.
3. Determine in what direction the planet is from the model Sun.
When we have determined these quantities for each planet, we will all go as a team and put stakes in the ground where the planets go (and put the planets on the stakes).

### Information on units:

1000 meters = 1 kilometer
100 centimeters = 1 meter
10 millimeters = 1 centimeter
1000 millimeters = 1 meter

It is often convenient to convert measurements to different units. For example, suppose you found that the distance to a model planet was 0.005 kilometers. We have no convenient way to measure this distance, since none of our measuring devices are marked in kilometers. However, if we multiply by 1, the number should not change:

```                     1000 meters
(0.005 kilometer) X -------------  =  5 meters
1 kilometer

```

## Planet Statistics

### Distances from the Sun to Planets

```Planet  Dist(kilometers)   Dist(miles)  Dist(minutes)
Mercury	   47,500,000	    29,500,000     2.64
Venus	  109,000,000	    67,600,000     6.06
Earth	  152,000,000	    94,300,000     8.44
Mars	  221,000,000	   137,000,000    12.3
Jupiter	  810,000,000	   503,000,000    45.0
Saturn	1,450,000,000	   904,000,000    80.6
Uranus	2,940,000,000	 1,830,000,000	 163
Neptune	4,510,000,000	 2,810,000,000	 251
Pluto	4,460,000,000	 2,780,000,000	 248
```

### Sizes of Planets

```Planet  Diam(kilometers)  Diam(miles)   Fraction of Earth
Mercury       4,880            3,032         0.38
Venus        12,100            7,519         0.95
Earth        12,756            7,927         1.00
Mars          6,784            4,215         0.53
Jupiter     143,200           88,984        11.20
Saturn      120,000           74,568         9.41
Uranus       51,800           32,189         4.10
Neptune      49,500           30,759         3.90
Pluto         2,600            1,616         0.20
```

### Size of the Sun:

1,392,000 kilometers
865,000 miles
109 times as large as the earth

## Our Model of the Universe

Fill in this table:
```Planet  Distance   Diameter    Angle
Mercury                         112
Venus                           262
Earth                           315
Mars                             52
Jupiter                         227
Saturn                          338
Uranus                          294
Neptune                         292
Pluto                           237
```

## Teachers' Guide

The distances and angles of the planets are for August 7, 1994. By using the current date instead of the mean distance, we saved about 150 meters of walking. The whole model took about 600 meters of land, but it could be much larger depending on the current position of Pluto and the angles between Neptune, Pluto, and Uranus. To measure the distances, we practiced taking one meter steps with a 3 meter ruler. We found that in practice, most people under-estimated the distance to the outer planets with this method (by about 25%), but they got the idea. Another approach is to get an aerial map of the area you're using, and marking on the map where the planets go, and putting them there.

Even using this large tract of land, the largest planet (Jupiter) is 1.4 cm and the smallest planet (Pluto) is 0.26 mm. The students went out with their "planets" and a stake to put in the ground next to it so they could find them later (we put the planets in bottle tops next to the stakes). Here are some suggestions for planets:

```Planet    Size    Object
Mercury .49 mm  pencil lead, sand
Venus   1.2 mm  poppy seed
Earth   1.3 mm  tip of a rice grain