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Planet Size Comparison

Planet Size Comparison

Launch Tool

Mercury is the second smallest planet; only Pluto is smaller. In fact, Mercury is not much larger than our moon. In this animation, you can find out how Mercury "sizes up" to Earth or any other planet. The first two planets that show up on the screen when you open this animation are Earth and Mercury. At the top of the screen, students can choose what planets they want to compare. At the bottom of the screen, students can see the dimensions for each planet as well as how they compare in size.

This animation was created before scientists in the International Astronomical Union voted for a new definition of a planet, which effectively removed Pluto from the list. So, Pluto is included in this animation. You may want to alert students to this fact. You also could use this as an opportunity to discuss with your students how scientists reach these kinds of decisions and what constitutes a planet.


For Educators

Planet Size Comparison can be used to enhance students’ understanding of our solar system and to help them gain a better appreciation for the sizes of the nine planets, plus the sun and the earth’s moon. This animation would be useful when addressing the Physical Setting benchmarks that focus on the universe. It could also be used when doing lessons on scale, models, systems, or displacing the earth from the center of the universe. When doing a lesson on scale, for instance, this animation could be used to allow students to see the relative sizes of the planets by comparing any planet against another and viewing them at the same scale. So, students not only get a visual image of two planets next to each other, they also can see the diameters of the planets and a ratio in which the diameter of the smaller object is taken to be one unit.

One feature of this animation of which you should be aware is that the size of the planets as they appear on the screen may vary depending on the size of the planets next to them. For instance, even if students keep the Earth in the left-hand screen as they compare it to other planets, its size may change from how large it appears when compared to Mercury versus the sun. This could cause some confusion among students so you may want to make sure that they understand that the size of a plant on the screen may vary simply due to the limitations of the animation itself.

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Tool Details

Grades Themes Type Project 2061 Benchmarks State Standards
AAAS Thinkfinity