Our question last week about the weight of the Sun got a lot of kids thinking. Our fan Dillon M. then asked, how do we measure the distance from the Earth to the Sun? Well, there are a couple of ways to do it. Back in ancient Greece, Aristarchus figured it out by waiting for a half-moon, then looking at the angle of light from the Sun hitting the Earth and making a triangle. But now that we know how big and how far the Moon is, we have an easier way. Ever notice how the Sun and Moon look the same size in the sky? That’s because the Sun is 400 times as wide – nearly 800,000 miles compared to 2,000 —* **and* it’s about 400 times as far. The Moon is 240,000 miles away, so that would give us 96 million miles for the Sun. That’s not too far off from the answer, but too far to go there for the day!

*Wee ones:* The Sun is much bigger than Earth, which is bigger than the Moon. Find 3 objects and put them in a row from biggest to smallest.

*Little kids:* Turn on a light, and hold a pencil sticking straight up from a table. Is its shadow longer or shorter than the pencil? *Bonus:* If the pencil is 5 inches tall and its shadow is twice as long, how long is the shadow?

*Big kids:* The Moon takes about 15 days to go from half-moon facing right (a “D”) to half-moon facing left (a “C”). If the D happens on Tuesday, what day will the next half-moon be? *Bonus:* The Moon actually takes 29 days to go all the way around once. How long is exactly half of that?

*The sky’s the limit — literally:* If the Sun were exactly 100,000,000 (100 million) miles away and you could fly 25,000 miles each day, how soon could you get there? (*Hint if needed:* How long would it take to fly 100,000 miles?)

__Answers:__

*Wee ones:* Items might include a book, a toy, a stuffed animal, or a shoe.

*Little kids:* Different for everyone…the lower/more to the side the light is, the longer the shadow. *Bonus:* 10 inches.

*Big kids:* On a Wednesday. *Bonus:* 14 1/2 days.

*The sky’s the limit:* 4,000 days, which is more than 10 years!

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.