# Big Space: The Scale of the Solar System

Bring Science Home: Activity 14

How much space? Image: Kagen McLeod

• Overview

• Overview

• Overview

• Overview

• Overview

• ### Gravity's Engines

We’ve long understood black holes to be the points at which the universe as we know it comes to an end. Often billions of times more massive than the Sun, they...

Key concepts
Solar system
Space
Planets

From National Science Education Standards: Objects in the sky

Introduction
Have you ever built a model of the solar system for school—or even just seen a picture of the solar system in a book? The planets are usually pretty close together—and close to the sun. In the real world (that is, in the real solar system) the planets are incredibly far apart from one another and from the sun (which is a good thing for us; if Earth were close to the sun, it would be too hot for us to live!).

Background
The closest planet to the sun is Mercury, and it's about 36 million miles (57 million kilometers) from the sun. What about Earth? We're orbiting the sun at a safe—and comfortable—distance of 93.2 million miles (150 million kilometers).

That's a big distance to try to understand. But using some (very small) household objects and (a lot) of space on the floor or ground, we can get a better sense of just how far apart the sun and planets are, especially in comparison with their sizes.

To simplify the distances in this activity, you can use short-cut measurements, such as the length of an adult foot for each foot or the length of an adult walking pace for each yard or meter. We'll provide exact standard and metric measurements below.

Materials
•    Nine small, round objects about the size of a peppercorn (0.1 inch, or 2.5 millimeters, across)
•    Measuring tape
•    Nine small pieces of paper labeled for the sun and planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune)
•    A clear, 21.5-foot- (6.6-meter-) long path on the floor inside or ground outdoors
•    A grapefruit (optional)
•    Two grains of table salt (optional)
•    Two grains of sea salt (optional)
•    35 feet (10.7 meters) of space in at least one direction (optional)

Preparation
•    How big is the solar system? Is it mostly crowded with planets or is it mostly empty space?
•    Try to clear a straight path that is 21.5 feet (8.6 meters) long. If you don't have that much room, clear at least four feet (1.2 meters) of space.

Procedure
•    Place the first peppercorn at one end of the path, and label it as the sun.
•    Measure 3.3 inches (eight centimeters) and place the second peppercorn. Place the label for Mercury next to it—it's the closest planet to the sun. (If we were making a scale model of the solar system, it would not be the same size of the peppercorn sun, but it would be practically invisible to the naked eye: 0.0002 inch, or 0.005 millimeter, across!)
•    Return to the sun and measure out 6.2 inches (15.7 centimeters). Place the third peppercorn and label it Venus.
•    Do you know what the next peppercorn will represent? Can you guess how far it will be from the sun?
•    Measure 8.6 inches (21.8 centimeters) out from the sun, and place the next peppercorn—this one represents Planet Earth!
•    The next planet is Mars, and it should be placed 13.1 inches (33.3 centimeters) from the sun.
•    Return to the sun and now measure out three feet, 8.2 inches (1.1 meters) before placing the next peppercorn. Label this planet Jupiter. (This is the largest planet, but if the sun were the size of a peppercorn, it would still be smaller than grain of table salt.)
•    The next peppercorn will be Saturn, which would be six feet, 10 inches (2.1 meters) from the sun.
•    Now measure 13 feet, nine inches (4.2 meters) from the sun before placing the next peppercorn, which is Uranus.
•    The last planet in our solar system is Neptune. Measure out 21 feet, 6.6 inches (6.6 meters) from the sun and place your final peppercorn and planet label there.
•    Stand next to the Neptune peppercorn and look at the sun. If you lived on Neptune, would the sun look as big as it does from Earth? The sun throws out a tremendous amount of light and heat, but how much of it would Neptune get as compared with Earth?
•    Extra: Want to get a better sense of how small the planets are compared with the sun? Try using a grapefruit—about four inches (10 centimeters) in diameter—as the sun. If the planets were to be proportionally sized and spaced in this model, Mercury—the closest planet to the Sun—would be a grain of table salt 13 feet, 10.5 inches (4.2 meters) away. Venus would be about the size of a grain of sea salt 25 feet, 10.7 inches (7.9 meters) away from the sun. And Earth would also be about the size of a rough grain of sea salt—35 feet, 8.2 inches (10.9 meters) away from the sun. What about Neptune? It would be more than 1,416 feet (431.6 meters) away from a grapefruit-size sun.
•    Extra: Want to try building a solar system with other size objects? Try plugging in their sizes in the Exploratorium's Build a Solar System Model calculator.

Read on for observations, results and more resources.

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1. 1. heavyrunner 09:14 AM 5/19/11

What happened to Pluto?

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2. 2. heavyrunner 09:14 AM 5/19/11

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3. 3. voyager4383 09:29 AM 5/19/11

"heavyrunner" --> Pluto has since been demoted to a dwarf planet due to it's size, and is no longer considered one of our main planets. (Who knows why that change was deemed important, but apparently it was!)

http://www.scientificamerican.com/article.cfm?id=astronomers-relegate-plut

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4. 4. Whup 08:34 PM 5/19/11

This is great. I am off to draw it in my driveway.

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5. 5. patcabtr 05:48 AM 5/20/11

Using Pluto could have been a great learning tool in scince class.

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6. 6. NoToe 06:41 AM 5/20/11

The reason elaborate ideologies have to be created about space is because the creation of space is not fully understood. The creation of space is a two part system. All things in the universe want to collapse and recoil and expand unless acted upon by another force. To deny this is to deny the creation of this universe. The collapsing force that created this universe has never ceased. It collapses one moment after the next each time creating a larger void to expand into creating more space.

Matter consumes the collapsing force which creates more space and creates gravity. This is why more space can hold less matter per space. Smaller spaces can hold more matter per space because they become a larger part that consumes the collapsing force as a whole.

Matter collapses but no longer collapses into itself and recoils to expand out into space like the last big bang it is held in check by black holes. The expansion and collapsing of matter bypass each other in each new moment. The collapsing force rotates as it collapses in. It is why all things spin. The collapsing force collapses in as a sphere and the frame of reference is at the equator. Heading into positive expanding time gives the right hand rule of thumb. Matter collapsing in the left hand rule of thumb on the other side of the equator on a collapsing sphere is pulled into a black hole.

Not expanding with the expansion force of the universe creates a density problem. Standing still because the consumption of space is greater than the expansion rate of space creates black holes.

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7. 7. NoToe 06:43 AM 5/20/11

Sorry I put the last post in the wrong place.

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8. 8. EmilyCragg 03:59 PM 5/20/11

You have to believe "they" know how to measure across the expanse. Personally, having re-rendered literally thousands of NASA photos, I find their measurements and distances incredible when compared to surface features. I mean, they're off by a factor of THOUSANDS, but I'm in no position to ascertain true measurements myself. So I can't say much, just, Wow! what an imagination they have!

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9. 9. Wayne Williamson 08:54 PM 5/23/11

Another cool article...thanks...
EmilyCragg...have no idea what your referring to...we defintitely know the distances to the the planets in our solar system....the spaces probes pioneer and voyager have more than proved it....

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