The Earth feels flat, but we’re really standing on a giant ball of land and ocean. What’s more, the inside of Earth isn’t all rock and dirt. If you dig down a few miles, you reach the “mantle,” which is crumbly and can move. 1,800 miles below that, you reach the outer core, which is super-hot liquid. Finally 1,400 miles below that is a solid ball, the inner core. It is white-hot, almost 11,000 degrees! So baker Rhiannon at cakecrumbs.me baked an amazing cake to show these layers. She made vanilla buttercake for the white core, yellow lemon cake for the outer core around it, and red Madeira sponge cake for the mantle layers. Throw on some blue and green marshmallow fondant (stiff icing) for the outside, and we have an Earth you can eat!
Wee ones: Earth is a giant round ball. Can you see any round ball shapes in your room?
Little kids: How many colors can you count in the cake — both the inside and outside? Bonus: If she cut the cake into 10 slices and you ate 2 of them, how many pieces would be left?
Big kids: This half-Earth cake looks like it could serve 12 slices. How many same-size slices would a whole Earth cake serve? Bonus: If the baker needed 2 cups of white batter, twice as much yellow batter as white, and 3 times as much red as yellow, how many cups did she need in total?
The sky’s the limit: This cake is about 1 foot wide. Earth is about 8,000 miles wide. If there are about 5,000 feet in a mile, about how many times as wide is our real Earth compared to this cake?
Wee ones: Answers might include soccer balls, beach balls and other toys, or the round part of a light bulb.
Little kids: We see 5 major colors: white, yellow, red, blue and green. Bonus: 8 slices.
Big kids: 24 slices. Bonus: 18 cups of batter, since you need 4 cups of yellow and 12 cups of red.
The sky’s the limit: 40,000,000 (40 million) times as wide!
Laura Bilodeau Overdeck is founder and president of Bedtime Math Foundation. Her goal is to make math as playful for kids as it was for her when she was a child. Her mom had Laura baking before she could walk, and her dad had her using power tools at a very unsafe age, measuring lengths, widths and angles in the process. Armed with this early love of numbers, Laura went on to get a BA in astrophysics from Princeton University, and an MBA from the Wharton School of Business; she continues to star-gaze today. Laura’s other interests include her three lively children, chocolate, extreme vehicles, and Lego Mindstorms.