Make a scale model of the Solar System and learn the REALdefinition of "space."

This Page requires a JavaScript capable browser.

Fill in the diameter of the Sun you want your model to be scaled by. You can fillin either the red bordered inches box or the green bordered millimeters box.Important: Only fill in one box. If both are filled in you will get a dialog boxasking you to clear one of the boxes. Use the Clear button to clear the entireform.

Click on the "Calculate" button.

Notice that the distances and sizes of the planets will automatically fill in. I'vealso provided some other interesting scale comparisons at the bottom of thechart.

You can now build your scale model. You can do this with a long tape measure,or you can measure the size of your pace and walk it off counting the number ofsteps you take. To mark a planet's place you can use a piece of paper on a postthat you stick into the ground, or you can use a flag, or even a person. Beprepared for a long walk!

If you build your solar system on a roll of toilet paper, you can make the Sunabout .4 inches (10 mm) across and still fit the entire solar system on the roll. Astandard roll of toilet paper has about 450 sheets that are about 4.375 incheslong, hence the roll is about 164 feet long. You should check your toilet paperfor length. Some are longer.

You can click on the names of the planets and satellites to go the the NinePlanets web site page about them. LOTS of info there!

Solar System Model

Body

BodyDiam(km)

BodyDiam(in)

BodyDiam(mm)

Orbitradius(km)

Scaled orbitradius

(ft & in)

Scaledorbit

radius(meters)

Sun 1391900 27.4 696 Calculate Clear

Mercury 4866 0.0957 2.4 57950000 95 ft 0.82 in 28.977 m

Venus 12106 0.2383 6 108110000 177 ft 4.3 in 54.058 m

Earth 12742 0.2508 6.3 149570000 245 ft 4.5 in 74.79 m

Mars 6760 0.133 3.3 227840000 373 ft 9.36 in 113.928 m

Jupiter 142984 2.8148 71.4 778140000 1276 ft 6.81 in 389.097 m

Saturn 116438 2.2922 58.2 1427000000 2341 ft 0.56 in 713.551 m

Uranus 46940 0.924 23.4 2870300000 4708 ft 10.02 in 1435.253 m

Neptune 45432 0.8943 22.7 4499900000 7382 ft 3.07 in 2250.111 m

Pluto 2274 0.044 1.1 5913000000 9700 ft 6 in 2956.712 m

Other interesting distances and speeds

QuantityReal

Quantity

ScaledQuantity(English)

ScaledQuantity(Metric)

Speed oflight

299792 km/sec 5.901 in/sec 149.9 mm/sec

Lightyear

9.46051E+12 km 2939.4 mi 4730.5 km

Distances to Stars and GalaxiesTo Alpha Centauri 4.03964E+13 km 12551.4 mi 20199.6 km

To Sirius 8.17388E+13 km 25396.8 mi 40872.3 km

To Deneb 1.32636E+16 km 4121105.5 mi 6632276.4 km

To Galacticcenter

2.62151E+17 km 81452391.1 mi 131084917 km

Sizes of StarsHottest star(Type 05)

12527100 km 20.55ft 6.26 m

Coolest star(Type M5)

222704 km 4.38 in 11.13 cm

Red giant 521962500 km 856.2 ft 261 m

(Betelgeuse)White dwarf(Sirius B)

13919 km 0.274 in 6.96 mm

Neutron star 20 km 0.000393 in 0.01 mm

I've only given you the sizes and distances to the planets. If you'd like tosee the satellites of the planets as well, click here for a much moreextensive page (and a longer download time too!)

One of the most exciting excercises I ever did as a kid was to make a scale model ofthe Solar System. Most of the pictures in my books made the distance betweenplanets seem small and easy to travel. Museums were no help either. The modelsthey displayed usually had the sizes of the planets to scale, but the distancesbetween them were a completly different scale, giving the impression of a ratherclose-knit family.

I made my first scale model on a roll of teletype paper tape (anyone remember thatstuff?) On this 1-inch tape, my Sun was the size of the tape - 1 inch in diameter. Itall started out well. Mercury was only about 3-1/2 feet from the sun and Earth wasalmost 9 feet from the Sun. What I didn't bargain for was that Pluto was 354 feetdown the tape! I used up almost the entire roll.

I also calculated the sizes that I should make the dots that represented the planets. Ifound that even the largest planet, Jupiter, should have a spot size smaller than 1/8inch. The other planets, especially the small rocky inner planets, would be virtuallyinvisible dust spots.

Needless to say, this was an eye-opening experience. This one excercise taught methe real meaning of the word "space." It sure made me feel insignificant looking atthe scale of the Solar System - never mind the rest of the universe!

Now we have great tools like spreadsheets to do the numerical computations for us.Below you can download OpenOffice or Excel format files. In this spreadsheet, youset the scale of the model by entering a radius for the Sun. The sheet should thencalculate everything else based on this number.

Download OpenOffice-format spreadsheet (25 kbytes)

Download Excel-format spreadsheet (45 kbytes)

Links to other Solar System resources

Your Age On Other Worlds

Your Weight On Other Worlds The Exploratorium's "Observatory" The Nine Planets A Solar System Scale Model Meta Page. Another downloadable spreadsheet from Planeten Paultje in the Netherlands. A new geocaching model in California. Get out that GPS to find the planets! New Jersey Astronomical Association Solar System Walk And Yet Another Model In Maine! Solar System Exploration from NASA-JPL NSSDC Photo Gallery JPL's Welcome to the Planets A diagram of the solarsystem NOW! (In stereo if you want!) Astronomy Picture of the Day Proportional Planets

Thanks to Bill Arnett for his fantastic Nine Planets web site.

© 1997; Ron Hipschman, Exploratorium

7/24/15, 2:36 PMBuild a Solar System

Page 1 of 4http://www.exploratorium.edu/ronh/solar_system/all_bodies.html

Make a scale model of the Solar System and learn the REAL definitionof "space."

You must have JavaScript turned on in your browser!

Fill in the diameter of the Sun you want your model to be scaled by. You can fill ineither the red bordered inches box or the green bordered millimeters box. Important:Only fill in one box. If both are filled in you will get a dialog box asking you to clearone of the boxes. Use the Clear button to clear the entire form.

Click on the "Calculate" button.

Notice that the distances and sizes of the planets will automatically fill in. I've alsoprovided some other interesting scale comparisons at the bottom of the chart.

You can now build your scale model. You can do this with a long tape measure, or youcan measure the size of your pace and walk it off counting the number of steps youtake. To mark a planet's place you can use a piece of paper on a post that you stickinto the ground, or you can use a flag, or even a person. Be prepared for a long walk!

If you build your solar system on a roll of toilet paper, you can make the Sun about .4inches (10 mm) across and still fit the entire solar system on the roll. A standard rollof toilet paper has about 450 sheets that are about 4.375 inches long, hence the roll isabout 164 feet long. You should check your toilet paper for length. Some are longer.

You can click on the names of the planets and satellites to go the the Nine Planets website page about them. LOTS of info there!

Body

BodyDiam(km)

BodyDiam(in)

BodyDiam(mm)

Orbitradius(km)

Scaled orbitradius

(ft & in)

Scaledorbit

radius(meters)

Sun 1391900 27.4 696 Calculate Clear

Mercury 4866 0.0957 2.4 57950000 95 ft 0.82 in 28.977 m

Venus 12106 0.2383 6 108110000 177 ft 4.3 in 54.058 m

7/24/15, 2:36 PMBuild a Solar System

Page 2 of 4http://www.exploratorium.edu/ronh/solar_system/all_bodies.html

Earth 12742 0.2508 6.3 149570000 245 ft 4.5 in 74.79 m

Moon 3476 0.0684 1.7 384403 0 ft 7.56 in 0.192 m

Mars 6760 0.133 3.3 227840000 373 ft 9.36 in 113.928 m

Phobos 22 0.0004 0 9408 0 ft 0.18 in 0.004 m

Deimos 12 0.0002 0 23457 0 ft 0.46 in 0.011 m

Jupiter 142984 2.8148 71.4 778140000 1276 ft 6.81 in 389.097 m

Metis (XVI) 40 0.0007 0 128000 0 ft 2.51 in 0.064 m

Adrastea (XIV) 20 0.0003 0 129000 0 ft 2.53 in 0.064 m

Amalthea (V) 188 0.0037 0 181400 0 ft 3.57 in 0.09 m

Thebe (XV) 100 0.0019 0 222000 0 ft 4.37 in 0.111 m

Io (I) 3642 0.0716 1.8 421900 0 ft 8.3 in 0.21 m

Europa (II) 3130 0.0616 1.5 671200 1 ft 1.21 in 0.335 m

Ganymede (III) 5268 0.1037 2.6 1071000 1 ft 9.08 in 0.535 m

Callisto (IV) 4806 0.0946 2.4 1880000 3 ft 1.01 in 0.94 m

Leda (XIII) 16 0.0003 0 11110000 18 ft 2.71 in 5.555 m

Himalia (VI) 186 0.0036 0 11470000 18 ft 9.8 in 5.735 m

Lysithea (X) 36 0.0007 0 11710000 19 ft 2.52 in 5.855 m

Elara (VII) 76 0.0014 0 11740000 19 ft 3.11 in 5.87 m

Ananke (XII) 30 0.0005 0 20700000 33 ft 11.5 in 10.35 m

Carme (XI) 40 0.0007 0 22350000 36 ft 7.99 in 11.175 m

Pasiphae (VIII) 50 0.0009 0 23500000 38 ft 6.63 in 11.75 m

Sinope (IX) 36 0.0007 0 23700000 38 ft 10.56 in 11.85 m

Saturn 116438 2.2922 58.2 1427000000 2341 ft 0.56 in 713.551 m

Pan (XVIII) 20 0.0003 0 133583 0 ft 2.62 in 0.066 m

Atlas (XV) 30 0.0005 0 137670 0 ft 2.71 in 0.068 m

Prometheus (XVI) 92 0.0018 0 139350 0 ft 2.74 in 0.069 m

Pandora (XVII) 84 0.0016 0 141700 0 ft 2.78 in 0.07 m

Epimetheus (XI) 114 0.0022 0 151420 0 ft 2.98 in 0.075 m

Janus (X) 178 0.0035 0 151470 0 ft 2.98 in 0.075 m

Mimas (I) 398 0.0078 0.1 185540 0 ft 3.65 in 0.092 m

Enceladus (II) 498 0.0098 0.2 239040 0 ft 4.7 in 0.119 m

Tethys (III) 1060 0.0208 0.5 294670 0 ft 5.8 in 0.147 m

7/24/15, 2:36 PMBuild a Solar System

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Telesto (XIII) 30 0.0005 0 294870 0 ft 5.8 in 0.147 m

Calypso (XIV) 26 0.0005 0 294870 0 ft 5.8 in 0.147 m

Helene (XII) 33 0.0006 0 377400 0 ft 7.42 in 0.188 m

Dione (IV) 1120 0.022 0.5 377420 0 ft 7.43 in 0.188 m

Rhea (V) 1528 0.03 0.7 527070 0 ft 10.37 in 0.263 m

Titan (VI) 5150 0.1013 2.5 1221860 2 ft 0.05 in 0.61 m

Hyperion (VII) 286 0.0056 0.1 1481000 2 ft 5.15 in 0.74 m

Iapetus (VIII) 1436 0.0282 0.7 3560800 5 ft 10.09 in 1.78 m

Phoebe (IX) 220 0.0043 0.1 12954000 21 ft 3.01 in 6.477 m

Uranus 46940 0.924 23.4 2870300000 4708 ft 10.02 in 1435.253 m

Cordelia (VI) 26 0.0005 0 49752 0 ft 0.97 in 0.024 m

Ophelia (VII) 32 0.0006 0 53764 0 ft 1.05 in 0.026 m

Bianca (VIII) 44 0.0008 0 59165 0 ft 1.21 in 0.03 m

Cressida (IX) 66 0.0012 0 61767 0 ft 1.21 in 0.03 m

Desdemona (X) 58 0.0011 0 62659 0 ft 1.23 in 0.031 m

Juliet (XI) 84 0.0016 0 64358 0 ft 1.26 in 0.032 m

Portia (XII) 110 0.0021 0 66097 0 ft 1.3 in 0.033 m

Rosalind (XIII) 54 0.001 0 69927 0 ft 1.48 in 0.037 m

Belinda (XIV) 68 0.0013 0 75255 0 ft 1.48 in 0.037 m

Puck (XV) 154 0.003 0 86006 0 ft 1.69 in 0.043 m

Miranda (V) 472 0.0092 0.2 129400 0 ft 2.54 in 0.064 m

Ariel (I) 1162 0.0228 0.5 191800 0 ft 3.77 in 0.095 m

Umbriel (II) 1170 0.023 0.5 267200 0 ft 5.26 in 0.133 m

Titania (III) 1578 0.031 0.7 438600 0 ft 8.63 in 0.219 m

Oberon (IV) 1522 0.0299 0.7 586100 0 ft 11.53 in 0.293 m

Neptune 45432 0.8943 22.7 4499900000 7382 ft 3.07 in 2250.111 m

Naiad (III) 58 0.0011 0 48200 0 ft 0.94 in 0.024 m

Thalassa (IV) 80 0.0015 0 50000 0 ft 0.98 in 0.025 m

Despina (V) 148 0.0029 0 52600 0 ft 1.03 in 0.026 m

Galatea (VI) 158 0.0031 0 62000 0 ft 1.22 in 0.031 m

Larissa (VII) 193 0.0037 0 73600 0 ft 1.44 in 0.036 m

Proteus (VIII) 418 0.0082 0.2 117600 0 ft 2.31 in 0.058 m

Triton (I) 2706 0.0532 1.3 353100 0 ft 6.95 in 0.176 m

7/24/15, 2:36 PMBuild a Solar System

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Nereid (II) 340 0.0066 0.1 5900000 9 ft 8.15 in 2.95 m

Pluto 2274 0.044 1.1 5913000000 9700 ft 6 in 2956.712 m

Charon 1172 0.023 0.5 17500 0 ft 0.34 in 0.008 m

Other interesting distances and speeds

QuantityReal

Quantity

ScaledQuantity(English)

ScaledQuantity(Metric)

Speed oflight

299792 km/sec 5.901 in/sec 149.9 mm/sec

Lightyear

9.46051E+12 km 2939.4 mi 4730.5 km

Distances to Stars and GalaxiesTo Alpha Centauri 4.03964E+13 km 12551.4 mi 20199.6 km

To Sirius 8.17388E+13 km 25396.8 mi 40872.3 km

To Deneb 1.32636E+16 km 4121105.5 mi 6632276.4 km

To Galacticcenter

2.62151E+17 km 81452391.1 mi 131084917 km

Sizes of StarsHottest star(Type 05)

12527100 km 20.55 ft 6.26 m

Coolest star(Type M5)

222704 km 4.38 in 11.13 cm

Red giant(Betelgeuse)

521962500 km 856.2 ft 261 m

White dwarf(Sirius B)

13919 km 0.274 in 6.96 mm

Neutron star 20 km 0.000393 in 0.01 mm

Return to top page

© 1997; Ron Hipschman , Exploratorium

Want to melt those years away? Travel to an outer planet!

This Page requires a JavaScript capable browser.

Fill in your birthdate below in the space indicated. (Note you must enter the yearas a 4-digit number!)Click on the "Calculate" button.Notice that your age on other worlds will automatically fill in. Notice thatYour age is different on the different worlds. Notice that your age in "days"varies wildly.Notice when your next birthday on each world will be. The date given is an"earth date".You can click on the images of the planets to get more information about themfrom Bill Arnett's incredible Nine Planets web site.

MM DD YYYY01 01 2002 Calculate

MERCURY

Your age is

83.6 Mercurian days 55.7 Mercurian years

Next Birthday Sun, Jun 28, 2015

VENUS

Your age is

20.1 Venusian days 21.8 Venusian years

Next Birthday Wed, Jul 15, 2015

EARTH

Your age is

4900.1 Earth days 13.4 Earth years

Next Birthday Fri, Jan 1, 2016

MARS JUPITER SATURN

Your age is4757.4 Martian days 7.1 Martian years

Next Birthday Tues, Jan 17, 2017

Your age is11951.7 Jovian days 1.13 Jovian years

Next Birthday Mon, Sep 22, 2025

Your age is10889.3 Saturnian days 0.45 Saturnian years

Next Birthday Tues, Jun 17, 2031

URANUS

Your age is6805.8 Uranian days 0.15 Uranian years

Next Birthday Sat, Jan 5, 2086

NEPTUNE

Your age is7313.7 Neptunian days 0.08 Neptunian years

Next Birthday Sat, Oct 18, 2166

PLUTO

Your age is766.8 Plutonian days 0.053 Plutonian years

Next Birthday Fri, Aug 9, 2250

The Days (And Years) Of Our Lives

Looking at the numbers above, you'll immediately notice thatyou are different ages on the different planets. This brings upthe question of how we define the time intervals we measure.What is a day? What is a year?

The earth is in motion. Actually, several different motions all atonce. There are two that specifically interest us. First, the earthrotates on its axis, like a spinning top. Second, the earthrevolves around the sun, like a tetherball at the end of a stringgoing around the center pole.

The top-like rotation of the earth on its axis is how wedefine the day. The time it takes the earth to rotate fromnoon until the next noon we define as one day. Wefurther divide this period of time into 24 hours, each of

which is divided into 60 minutes, each of which is broken into 60seconds. There are no rules that govern the rotation rates of theplanets, it all depends on how much "spin" was in the originalmaterial that went into forming each one. Giant Jupiter has lotsof spin, turning once on its axis every 10 hours, while Venustakes 243 days to spin once.

The revolution of the earth around the sun is how we define theyear. A year is the time it takes the earth to make one revolution- a little over 365 days.

We all learn in grade school that the planets move at differingrates around the sun. While earth takes 365 days to make onecircuit, the closest planet, Mercury, takes only 88 days. Poor,ponderous, and distant Pluto takes a whopping 248 years for onerevolution. Below is a table with the rotation rates and revolutionrates of all the planets.

Planet Rotation Period Revolution Period

Mercury 58.6 days 87.97 days

Venus 243 days 224.7 days

Earth 0.99 days 365.26 days

Mars 1.03 days 1.88 years

Jupiter 0.41 days 11.86 years

Saturn 0.45 days 29.46 years

Uranus 0.72 days 84.01 years

Neptune 0.67 days 164.79 years

Pluto 6.39 days 248.59 years

Why the huge differences in periods? We need to go back to thetime of Galileo, except that we're not going to look at his work,but rather at the work of one of his contemporaries, JohannesKepler (1571-1630).

Kepler briefly worked with the greatDanish observational astronomer,Tycho Brahe. Tycho was a greatand extremely accurate observer,but he did't have the mathematicalcapacity to analyze all of the datahe collected. After Tycho's death in1601, Kepler was able to obtainTycho's observations. Tycho's

observations of planetary motion were the most accurate of thetime (before the invention of the telescope!). Using theseobservations, Kepler discovered that the planets do not move incircles, as 2000 years of "Natural Philosophy" had taught. Hediscovered that they move in ellipses. A ellipse is a sort ofsquashed circle with a short diameter (the "minor axis") and alonger diameter (the "major axis"). He found that the Sun waspositioned at one "focus" of the ellipse (there are two "foci", bothlocated on the major axis). He also found that when the planetswere nearer the sun in their orbits, they move faster than whenthey were farther from the sun. Many years later, he discoveredthat the farther a planet was from the sun, on the average, thelonger it took for that planet to make one complete revolution.These three laws, stated mathematically by Kepler, are known as"Kepler's Laws of Orbital Motion." Kepler's Laws are still usedtoday to predict the motions of planets, comets, asteroids, stars,galaxies, and spacecraft.

Here you see a planet in a very elliptical orbit. Note how it speeds up when it's near the Sun.

(Requires QuickTime Plugin)

Kepler's third law is the one that interests us the most. It statesprecisely that the period of time a planet takes to go around thesun squared is proportional to the average distance from the suncubed. Here's the formula:

Let's just solve for the period by taking the square root of bothsides:

Note that as the distance of the planet from thesun is increased, the period, or time to makeone orbit, will get longer. Kepler didn't know thereason for these laws, though he knew it hadsomething to do with the Sun and its influenceon the planets. That had to wait 50 years for Isaac Newton todiscover the universal law of gravitation.

The Gravity Of The Situation

Closer planets revolve faster, more distant planetsrevolve slower. Why? The answer lies in howgravity works. The force of gravity is a measure ofthe pull between two bodies. This force depends ona few things. First, it depends on the mass of thesun and on the mass of the planet you areconsidering. The heavier the planet, the strongerthe pull. If you double the planet's mass, gravity

pulls twice as hard. On the other hand, the farther the planet isfrom the sun, the weaker the pull between the two. The forcegets weaker quite rapidly. If you double the distance, the force isone-fourth. If you triple the separation, the force drops to one-ninth. Ten times the distance, one-hundredth the force. See thepattern? The force drops off with the square of the distance. Ifwe put this into an equation it would look like this:

The two "M's" on top are the sun's mass and the planet's mass.The "r" below is the distance between the two. The masses arein the numerator because the force gets bigger if they getbigger. The distance is in the denominator because the force gets

smaller when the distance gets bigger. Note that the force neverbecomes zero no matter how far you travel. Knowing this lawhelps you inderstand why the planets move faster when they arecloser to the sun - they are pulled on with a stronger force andare whipped around faster!

LINKSYour Weight On Other Worlds

Build A Solar System

The Exploratorium's "Observatory"

The Nine Planets

Other nerdy dates you should celebrate!

Views of the Solar System

NSSDC Photo Gallery

NASA Jet Propulsion Laboratory, Pasadena,

Ever wonder what you might weigh on Mars or The Moon? Here's yourchance to find out.

This Page requires a JavaScript capable browser.

Fill in your weight below in the space indicated. You can enter your weight in anyunit you wish.Click on the "Calculate" button.Notice that the weights on other worlds will automatically fill in. Notice that yourweight is different on the different worlds.You can click on the images of the planets to get more information about them fromBill Arnett's incredible Nine Planets web site.

100 Calculate

The PlanetsMERCURY

Your weight is37.8

VENUS

Your weight is90.7

THE MOON

Your weight is16.6

MARS

Your weight is37.7

JUPITER

Your weight is236.4

SATURN

Your weight is106.4

URANUS

Your weight is88.9

NEPTUNE

Your weight is112.5

PLUTO

Your weight is6.7

The Moons of JupiterIO

Your weight is18.35

EUROPA

Your weight is13.35

GANYMEDE

Your weight is14.48

CALLISTO

Your weight is12.64

A Few Different Types of Stars(better land at night to avoid burning your feet!)

THE SUN

Your weight is2707.2

A WHITE DWARF

Your weight is130000000

A NEUTRON STAR

Your weight is14000000000000

Mass and Weight

Before we get into the subject of gravity and how it acts, it's important tounderstand the difference between weight and mass.

We often use the terms "mass" and "weight" interchangeably in our daily speech,but to an astronomer or a physicist they are completely different things. The massof a body is a measure of how much matter it contains. An object with mass has aquality called inertia. If you shake an object like a stone in your hand, you wouldnotice that it takes a push to get it moving, and another push to stop it again. If thestone is at rest, it wants to remain at rest. Once you've got it moving, it wants tostay moving. This quality or "sluggishness" of matter is its inertia. Mass is ameasure of how much inertia an object displays.

Weight is an entirely different thing. Every object in the universe with massattracts every other object with mass. The amount of attraction depends on thesize of the masses and how far apart they are. For everyday-sized objects, thisgravitational pull is vanishingly small, but the pull between a very large object,like the Earth, and another object, like you, can be easily measured. How? All youhave to do is stand on a scale! Scales measure the force of attraction between youand the Earth. This force of attraction between you and the Earth (or any otherplanet) is called your weight.

If you are in a spaceship far between the stars and you put a scale underneath you,the scale would read zero. Your weight is zero. You are weightless. There is ananvil floating next to you. It's also weightless. Are you or the anvil mass-less?Absolutely not. If you grabbed the anvil and tried to shake it, you would have topush it to get it going and pull it to get it to stop. It still has inertia, and hencemass, yet it has no weight. See the difference?

The Relationship Between Gravity and Mass and Distance

As stated above, your weight is a measure of the pull of gravity between you andthe body you are standing on. This force of gravity depends on a few things. First,it depends on your mass and the mass of the planet you are standing on. If youdouble your mass, gravity pulls on you twice as hard. If the planet you arestanding on is twice as massive, gravity also pulls on you twice as hard. On theother hand, the farther you are from the center of the planet, the weaker the pullbetween the planet and your body. The force gets weaker quite rapidly. If youdouble your distance from the planet, the force is one-fourth. If you triple yourseparation, the force drops to one-ninth. Ten times the distance, one-hundredth theforce. See the pattern? The force drops off with the square of the distance. If weput this into an equation it would look like this:

The two "M's" on top are your mass and the planet's mass.The "r" below is the distance from the center of the planet.The masses are in the numerator because the force getsbigger if they get bigger. The distance is in the denominatorbecause the force gets smaller when the distance gets bigger.Note that the force never becomes zero no matter how far you travel. Perhaps thiswas the inspiration for the poem by Francis Thompson:

All thingsby immortal powernear or farto each otherhiddenly linked are.That thou cans't not stir a flowerwithout troubling a star.

This equation, first derived by Sir Isaac Newton, tells us a lot. Forinstance, you may suspect that because Jupiter is 318 times asmassive as the Earth, you should weigh 318 times what you weighat home. This would be true if Jupiter was the same size as theEarth. But, Jupiter is 11 times the radius of the Earth, so you are11 times further from the center. This reduces the pull by a factorof 112 resulting in about 2.53 times the pull of Earth on you.Standing on a neutron star makes you unimaginably weighty. Notonly is the star very massive to start with (about the same as theSun), but it is also incredibly small (about the size of SanFrancisco), so you are very close to the center and r is a verysmall number. Small numbers in the denominator of a fractionlead to very large results!

LINKSYour Age On Other Worlds

Build A Solar System

The Exploratorium's "Observatory"

The Nine Planets

Views of the Solar System

NSSDC Solar System page

NASA Jet Propulsion Laboratory, Pasadena, California

Astronomy Picture of the Day

Photo credits

©1997, Ron Hipschman

A Solar System Scale Model Meta PageThe idea: Making scale models of the solar system is a useful way to learn about it. Here are various relatedpages.

PagesSome general background info...

The Nine Planets and its An Overview of the Solar SystemExplore the Solar System interactive appletSun, Planet and Satellite Data

Scale model solar systems...

The Thousand Yard Model, or The Earth as a Peppercorn (This is the original booklet. There is also a second online version.)Here is an outdoor activity. Photos of another. A lesson plan. Another.10 The Size and Distance of the PlanetsScale Model Demonstrations of the Solar SystemSchoolyard Solar System (also here at NASA)Cosmic Wheels - Measuring the Orbits of Planets(PDF) (from here) a lesson planBuild A Solar System (online calculation)Solar System Live (current planet positions)Shows the real current layout of the inner and outer system, or both (using a bigger image).It also has "logarithmic" (the default) and "equal" distorted displays.Remember the Sun and planet icons are not to scale. Not even close.The Toilet Paper Solar SystemActivity: Toilet Paper Solar System and the Side note: why toilet paper? [or receipt paper]Night-Time Model Solar SystemGiant Solar System Model / AN INTERPLANETARY HIKEOur Solar System: The Planets and Their Motion

Make Models of the Planets - PrimaryMake Models of the Planets - IntermediateSolar System ModelOrbits and Properties of the PlanetsAlso The Sun and Earth Size ComparisonThese also appear with this url.

Boston Museum of Science's Community Solar System , Bicycle of the Solar System activity , andSize and Scale. (Also Welcome to the Universe and exhibit blurb.)The Boston Museum of Science Solar System has additional photos.The Eugene, Oregon Scale Model Solar System community solar systemLakeview Museum's Community Solar System (can be slow), and a related article.Distance and Scale: Activity 1 Part of Planetary Curriculum Module: NAVIGATING the SOLAR SYSTEM.Scale in the Solar System - ActivitiesAST 201, Fall 96, Lab 3: The Orrery (gone?)Scaled Solar System

Universal Proportions another lesson planA View from the Back of the Envelope 's Mega , Giga , and Terameters in your hands.Scale Model of the Solar SystemA demonstration of the relative sizes of the planets (and distances of the planets, and more)The Solar System StoryThe relative size of Earth, Jupiter, Sun (1 : 10 : 100)Solar System with balloons a lesson planSolar system temperature diagram from How did the Earth Get Here?Data Sheet for Model of Solar SystemHow Big is the Solar System?Sagan Planet Walk, a community solar system from Ithaca NY's Sciencenter. (A related article TAKE THEKIDS TO MARS is gone)Page 3: Planet Size Comparison ExerciseThe Living Solar System (under construction) from NOAO K-12 EDUCATIONAL OUTREACHACTIVITIESModel of THE SOLAR SYSTEMSOLAR SYSTEM ACTIVITIES FOR THE CLASS ROOMA Simple Scale Model of the Solar SystemCVSF - Scale (was "IT'S ALL A MATTER OF SCALE !")Student Project Sheet 3: More to ExploreThe Universe At Your Fingertips - ActivitiesTHE SOLAR SYSTEMA100 Homework 1Scale Solar System ModelScale Model of the Solar SystemSome objects - was part of this page.

Additions... (aka, What's new?)

Space Art: We Are the Solar SystemClay Planets (an older version)Making a Model of the Solar SystemSolar System SimulatorCalculating Measurements in SpaceGainesville Solar Walk with a list of other models.Foster Planet Walk at Aquinas College.A Solar System Scale Model for Pasadena - A Proposal.Community solar systems bring the celestial down to earthTours of Model Solar SystemsSweden Solar SystemWelcome to Cycle the Solar System in YorkColorado Scale Model Solar System and Voyage: A Scale Model Solar System For Washington DC andBeyondThe Maine Solar System Model and an article about it.Powers Of Ten-like: Quarks to Quasars, CERN's, Cosmic View, another, How Big Are Things?(drafty).Project PLATO Lesson Plan - scalingThe Orrery (Science U)North Georgia Astronomers' Millennium Project, aka The Gainesville/Hall County ScaleModel/Walking Tour of Our Solar SystemThe Virtual Solar System Scale modelWhat colour is the Sun? and my What color is the Sun?.

The Earth, The Sun, and The Moon - Grade 1 (some interesting activities)Scale of the solar systemPlanetary Icosahedrons (fold your own globes!)SURFACE OF THE EARTH ICOSAHEDRON GLOBE (mail order, but cheap)Making globes of the planetsSize Scales in AstronomyAn example of combining Solar System Scale Model resourcesInterstellar scaleMadison Planet Stroll in WisconsinOur View of the Solar System and Solar System Stroll Activity lesson plansClassroom Activity: A Grapefruit SaturnASTRO UTAH Scrunch the UniverseASTRO UTAH Solar System SpreadsheetOur Solar System Gallery - The Thousand Yard Model (page 5) (PDF)A Stroll Through the Solar System (PDF)(gone?)Build Your Own CometFebruary 2001 Colorado Springs Astronomical Society Journal of High Altitude Observing (President'sCorner, page 2) (PDF)Planet Trail in AustriaLowell Observatory Pluto Walk with photosVoyage - A Journey Through Our Solar SystemHarry's "Comparative Astronomy" Pages (Or: how much we can get out of drawing circles)A Scale Model Demonstration of the Solar System (PDF)Java models, which may crash your browser. None of the planet dots are to scale.Explore the Solar System , Solar system view , The "Visible" Solar System and others , Ulysses in the3D Solar System , Comet Halley's Orbit in the Solar System , Solar System Viewer , and moons [moondots are not to scale] , and create imaginary solarsystems , Travels in the Solar System , Animation:Our Solar System , Animation: Upsilon Andromedae vs Our Solar System , Voyager 1 and 2trajectories , Inner Solar System Model , A Scale Model of the Solar System [begins looking northward(opposite of usual)] J-Track 3D [Earth only. Crashes my browser.]Solar System ModelsSolar System Scale Modeler another online calculatorAstronomy for Simple Minds musing [some mistakes, "pops down" an ad window]The Scale of the Solar System and Nearby StarsHagen community solar systemPlateful of Planets and The Dynamic Solar System activities from Paper Plate EducationSilver City's Sidewalk Solar SystemBringing the Solar System Down to Earth (lesson plan)Bonsall Elementary Model Solar SystemSolar System Scaled Down: Lesson on ProportionsScale Model of Our Solar System (activity)Teacher page, Schoolyard Solar System science lessonENC Scale Model Solar System LabA Sense of Scale8th grade drawing scaled down solar systemHow big is the solar system? by John SilveiraSolar System on a StringSolar System- Making a Scale Model [DOC] (as html)Journey Through The Solar System"Alpha Centauri placed 100 yards away" [PDF]

Other ideasA planetary scavenger hunt - `in which students try to find planets in the grass outside their school byusing a length of string that they have cut to the relative distance that the planet should be from thesun.' (Part of a teaching module for high school science classes, being developed as part of the `MercerCounty Science Alliance program in New Jersey'. [Pointer from Daniel Fishman<dfishman@sarnoff.com>. Thanks.])Use your head - "imagine your own head as a model Earth. If you're in the northern hemisphere,imagine North America on the right side of your forehead and South America sitting on your leftcheek, dripping off your chin like a kind of continental goatee. Africa is hung over your left ear, andEurasia forms a skullcap across the back of your head. The right side of your head is almost all PacificOcean except for Australia, located "down under" and behind your right ear. [Turning your head,bring...] locations on your model Earth around to experience sunrise, noon, sunset, and midnight.Where is the Sun rising while your part of the Earth sees it setting? Which part of the world is sleepingwhile you eat your lunch?" ["Getting a Global Sense" by LuAnn Dahlman, in Mercury, May-June 1998p6]"When I was a kid I used to build scale models in my back yard with marbles, etc. then and look at itthrough my telescope." [a reader]

I wonder if the models have more potential than is usually utilized. One might have an intermittent rule `noone is allowed tomove around the area any faster than light speed'. Or compress time and run the planets around, recapping students' lifetimes ina few minutes. Add Voyagers as out of plane elements to give a sense of depth and of gravity as something that can be playedwith. Include context, like the lay of the galactic plane, the direction to the core. Solar wind and heliopause, to make thesurrounding void also interesting. There seem lots of potentially neat ideas. If your club does construct a model, perhaps a write-up, reflections or report, for the net...? "Trip reports" are often both easilydone and fun to read.Using receipt paper: For the Toilet Paper Solar System, a reader suggests cash-register receipt paper asmore durable. The tradeoff is loss of premeasurement and humor.

What I would like to see...- A web-based "spreadsheet" which allows one to give/take objects (lightbulb, marble, various balls, etc),rather than just measurements.- Scaled orbital and solar system velocities too, even though they are rather small in realtime.- Adjustable time so one can do `run around the room for five years'.- Kid-accessible descriptions of "invisible" solar system structure (solar wind and planetary envelopes andwakes)- Light issues (running around at light speed, truncated light cones from flashing flashlights, etc)- A visual spreadsheet webpage. So a `not necessarily numerate child' (though I'd enjoy it too) could just clickamong `If the Sun (picture) is the size of a: [lightbulb (picture)], [pin-head (picture)], ..., Earth the size of a:[globe (picture)], etc', and get a diagram of the solarsystem - pictured on a desktop if it fits, or in a room, oramidst cars and buildings, an air-photo of a town, a map, the Earth, etc. With appropriately sized objectssuggested for the planets and such. If the page took an background image url and meter/pixel number, folkscould create links customized with local maps.- ...

Background:There are several scale model of solar system pages out there, but at the moment (1997.Mar.04), they do not

seem to be well interconnected. This page is intended to provide interim interconnection. As sites dedicatedto astronomy/education take up this content, this page will eventually be phased out. This grew out of ausenet posting of mine. Contributions welcome.Interconnection is improving (1998.Mar.04), but has a ways to go. This page remains supported. Commentsencouraged.

Comments encouraged. - Mitchell N Charity <mncharity@vendian.org>. [Top]Notes: Bos Sci Mus has a board with halved/embedded balls: marble, ball bearing, flecked translucent ball, ping-pong, golf, wiffle, soft, soccer, basket for a `match planet to ball' exercise.

Doables: Too big - reorg! So many links now - time to review page organization. Add inflatable earth/moon/mars planet ball/globes? Find some VRML. glissando.gsfc.nasa.gov/vu a candidate, but looks abandoned. Automate Excite "documents like this one" neighborhood exploration.

History: 2003-Aug-23 Added 1 link. Thanks to a reader. 2003-Aug-10 Added 13 links. Fixed 2. 2003-Jun-08 Added 2 links. 2003-Apr-22 Added 2 links. Thanks to a reader. 2003-Apr-12 Added reader comment re receipt paper. 2003-Apr-11 Added Hagen css link. Thanks to a reader. 2003-Feb-04 Repaired links - 4 added, 6 changed, 3 flagged, 4 removed, 1 left. 2002-Dec-14 Migrated 1 link. 2002-Sep-10 Added `Java model' section and links, 3 other links, and a reader quote. Changed contact email, and linked homepage. 2002-Jul-31 Fixed 1 link. Thanks to the site author. 2002-Jul-30 Added 2 links. 2002-Jul-19 Added 16 links. Fixed 7 (related) links. Fixed 4 links. Removed 3 dead links. 2002-Jun-23 Added link. 2002-May-27 Updated link. 2002-May-06 Added `Madison Planet Scroll'. 2002-Feb-20 Added link. Thanks to a reader. 2002-Jan-01 Updated link. Removed `Dec special'. 2001-Nov-28 Added link. Added `live schoolyard example', as `Dec special'. Edited SSLive. 2001-Nov-16 Added link. 2001-Nov-14 Added link. 2001-Oct-20 Added `Planetary Icosahedron' - thanks to a reader. Added 4, flagged 1, fixed 4. 2001-Jun-05 Added 2 links. 2001-May-21 Added 2 links. 2001-Apr-10 Added 2 links. Restored one. Flagged broken link. 2001-Feb-18 Added `Powers of Ten' links. Removed two new broken links, and Brokenness section w old ones. 2000-Oct-18 Added `Maine SMSS' - thanks to a (different) reader. 2000-Oct-06 Added `Colorado SMSS' - thanks to (the same:) reader. "Additions" moved above broken links, and indented. 2000-Oct-03 Added York's `Cycle the Solar System' - thanks to a reader. 2000-Oct-02 Added `Tours of' and `Sweden' - thanks to a reader. 2000-Sep-24 Added `Community [..] down to earth'. Fixed 4 links, flagged 2. Thank you readers for your positive feedback. :) 2000-Mar-09 Fixed a link. 2000-Mar-07 Fixed a formatting bug (an unclosed `small'). Shrank this History section to font size=-2. 2000-Mar-02 Added Pasadena proposal (Thanks to Charles Kohlhase). Link repair - 1 fix, 2 flagged. 2000-Jan-21 Added visual spreadsheet idea. Link repair. 1999.Dec.14 Link repair - fixed 2, dropped 1 `also here' link. 1999.Nov.11 Added Getty's `Space Art'. Link repair. 1999.Aug.14 Some link repair (they are now checked automatically). 1999.Jul.26 Checked links. Broken ones fixed, removed, or left labeled. 1999.Jun.09 Rusk's `Simple Model' moved. 1999.Jun.08 Added `Foster Planet Walk'. 1999.Mar.19 Added `Solar System Walk'. 1999.Mar.02 Added `Clay Planets', WSanford, `Explore' applet, `Simulator'. Thanks to a reader's search. 1999.Jan.26 Found relocated `Toilet Paper Solar System'. Thanks to author. 1999.Jan.20 Added `A Night-Time Model Solar System'. `Toilet Paper' link now broken. Some others. 1998.Dec.30 Fixed link for a relocated page.