Transcript for WALL-E Learns Proportions


Voice Over: NASA Education's WALL-E, take one, and--whoa, hey WALL-E, we're not ready, you're not on yet. Whoa--


[static] Cut. Marci: Guys? Are we ready? Hello?


[crash, static]


So I see you've met our special guest. Thanks, WALL-E. NASA has put people on the moon before, and the Lunar Reconnaissance Orbiter is mapping the moon so we can go back. Now when you've looked at the moon from your backyard, it looks really tiny. So how does NASA put a spacecraft on something so small? That's because it's probably not as small as it looks. So the question of the day is how big is the moon? And to answer that, we need to apply a proportion. That's right, WALL-E. A proportion is the relationship between things, such as the relationship between the size of the Earth and the size of the moon. To find the actual diameter of the moon, we can use two everyday objects to represent the relative sizes of the Earth and moon. Great idea, guys. A baseball is just about the right size for our moon. Now we need an Earth. Ooh, a basketball Perfect! Wait, don't--




[crash]Thanks, WALL-E.


So we can use the basketball as our Earth, and the baseball as our moon. A basketball is 24 centimeters in diameter, and the baseball is 7.5 centimeters in diameter. So let's apply our proportion. Baseball over basketball equals x, because that's what we're trying to find out, over the Earth's diameter. And we know that because we live here. So that's 12,756 km. Now, cross-multiply and solve for x. So we just solved that the moon's diameter is about 3900 km. But you should check to see if we're right. In any case, the moon is plenty big to land a spacecraft, to live and work on the moon in the future. To learn more, check out