Any two-dimensional representation of the solar system, as provided in the poster, makes it difficult to comprehend the vast size and distances involved. The first three ideas suggest ways to make the sizes and distances more concrete. The next two activities provide a fun way to learn more about the nature of each planet without focusing on memorizing a bunch of information. What we learn about the Sun depends on what kind of light (wavelength) we use to observe it. The last two activities provide a real-time look at the sun in visible light and then what we can learn from observing it in other kinds of light.

### Comparing the Size of the Planets

Everyone loves to play with playdough. This activity has students work in small groups to use a large ball of playdough to first predict how much of the ball goes into each planet, and then divide up the ball according to these instructions to see how well they did with their predictions. It also works well as a teacher-led demonstration if obtaining a large amount of playdough is a challenge. If you want to add Eris, another dwarf planet beyond Pluto, save a piece of playdough in Step 7 about the same size as Pluto. A fun follow-up activity is to ask the class how many Mars-shaped playdough balls it takes to make a playdough Earth. Most people are amazed that it takes more than six Mars balls to produce the Earth. Another fun way to explore the relative size of the planets is to use different food items to represent each planet. Learn more about this option at Wild About Here, or at this more detailed version.

### Comparing the Distance Between the Planets

This activity lets your students take the solar system home in their pockets. It uses a meter-long strip of adding machine tape to provide a fun way to see the relative distance between the planets, including the dwarf planet Pluto. To add Eris, one of the new dwarf planets, to the model, you will need two more meter-long strips of adding machine tape added at the end. This video is another way to introduce the vast distances between the planets and emphasizes that the planets are not in a straight line as is implied in many diagrams. Another National Geographic activity offers a different way to explore the distance between the planets by stepping the distance out on the school playground. For advanced students, you might challenge them to determine the easiest way to go from Earth to other planets, and how long it would take. This activity shows that the planets are not in a straight line, are moving with respect to each other, and are faster to reach  when they line up in a certain way.

### Comparing Both the Size and Distance in the Same Model

To truly comprehend the vast distances between the planets compared to the planetary sizes, one must build a model solar system that uses the same scaling factor for both the distance between the planets and the planetary sizes. This can be a great mathematics skill builder as students calculate the distances and sizes to fit inside your playground or school neighborhood. This activity makes it even easier by doing the calculations for you, once you decide on the scaling factor. Your students can easily change the scaling factor to see what works to make planets large enough to see and also provide distances that can be easily reached. Don’t be surprised when you want the smallest object to be at least 1mm and you find that you have to walk 2.5 km (about 1.5 miles) to reach Pluto. This version of the activity discusses alternatives of using a map of the school's neighborhood if you don’t want to walk that far. After doing the activity, your students will enjoy seeing this video of a model solar system built in the desert.  This other video also nicely reinforces the challenge of trying to show the planets’ sizes and the distance between them at the same time.

### Invent an Alien Creature

Nothing is more boring than writing a typical research report. This activity has students research the nature of the planets by creating a creature that could live on one of the planets based on the planet’s physical characteristics. See what a Martian might look like according to one student in Wisconsin. What might a Jovian creature look like that has to deal with 2.5 times Earth’s gravity and no solid surface to walk on? While the Martian is a two-dimensional image, it is even more fun to have the students build three-dimensional versions of their aliens. This is what students used to do for a nationwide contest in Canada that awarded major prizes like science fairs in the US. See the continuation of this contest in Manitoba, Canada. The National Geographic short videos about each planet are a great place to start to get information about the planets. Of course, your students should use their favorite search engine to find a number of resources. If you are looking for a creative writing connection to this activity, ask the students to write a science fiction or romance story based on their alien. This activity is a great lead-in to a discussion regarding the possibility of life on other planets in our solar system and elsewhere in the universe. National Geographic Explorer, Debarati Das(pictured above near this section's title), studies the possibility of life surviving deep in subsurface cracks on Mars. She explains more about her work in this video. To get students thinking about what a creature may need to live on another planet you can do this demonstration regarding what happens to a lit candle in a simulated Martian atmosphere.

### Travel Brochure for Other Planets

Another engaging way for students to learn information about the planets is to develop a travel brochure for future space farers on a vacation to a planet. What are the for-sure sights to see on a visit to Neptune? What should one wear and be sure to bring to survive the severe weather. This activity requires the same background used for the Invent an Alien Creature activity. It is also a great way to develop oral and visual presentation skills. Now that we have observed or visited a number of the smaller objects in the solar system (e.g. comets, asteroids, Pluto, Eris) you may want to include them as tourist destinations. See how others describe the activity at Planet Travel Brochure, Planet Brochure Project and NASA—Travel Agent. Students who are enthusiastic about space science and art can also get some inspiration from these beautiful Visions of the Future posters that are artist renditions for future space tourism!

### Demotion of Pluto

There was a public uproar in 2006 when astronomers demoted Pluto to a “dwarf planet.” How could astronomers do this to many people’s favorite planet that has the same name as their favorite dog? But this wasn’t the first time a planet was kicked out of the planetary club. In the 1800’s students had to memorize 11 planets instead of the current eight. The National Science Teaching Association (NSTA) developed an excellent learning experience (Why Isn’t Pluto a Planet Anymore?) to show how our understanding of the solar system has changed over the centuries. This is also the perfect time to update the traditional mnemonic to remember the order of the planets – My Very Eager Mother Just Served Us Nine Pizzas. Have your students create a new mnemonic without the “Pizzas” or by adding both Pluto and Eris to the list.

### Observing the Sun

Observing most astronomical objects is difficult because they are only visible at night and just appear as points of light. But the Sun provides a very bright astronomical object that is easy to observe during the day. First of all and most important, NEVER LOOK DIRECTLY AT THE SUN, as it can damage the back of your eye. While this caution may seem to present a problem, it is easy to project an image of the Sun on to a white piece of paper. Follow the instructions in this video or in this document to build your own Sun projector. Sunspots are easy to see if there are any on the Sun when you look. If you observe over a number of days, you can see the sunspots move due to the Sun’s rotation. Dedicated observers who do this over seven to 14 days can measure the Sun’s rotation rate.

### The Sun at Different Wavelengths

The solar image on the poster is a composite of three different images. To help your students understand what this means, have them search on the computer three different ways to see a human leg (e.g., search for an infrared image of human leg, visible light image of human leg, and x-ray of human leg). Visible light shows us what we see with our eyes, while infrared shows the temperature of different parts of the leg. An x-ray image allows us to see the bones under the skin. The composite image on the poster does the same thing for the Sun. Our eyes see what we call the surface of the Sun (the photosphere), although you could not walk on it any easier than on a boiling pot of soup. The photosphere is what you see when you projected an image of the Sun, if you did the Observing the Sun activity. Looking at the Sun at other wavelengths gives us different information and views, just like the different views of the leg. This website shows what we learn by looking at the Sun using different kinds of light. As a follow up to this activity, this National Geographic video provides a great summary of the Sun’s influence on all objects in the solar system, especially on our modern lifestyle on the Earth. If students get confused about the difference between solar flares and coronal mass ejections, this National Geographic video will help clarify the difference.