What makes a day, anyway? If you look down, you’re standing on a really, really big ball called Earth. As Earth turns in space, different parts face the Sun and get sunshine. That’s daytime. When your side turns away from the Sun, you have nighttime. It takes 24 hours to spin all the way around, which makes 1 full day. But other planets spin faster or slower. So our friend Ben W. asked, which planet has the longest day? It definitely isn’t any of the big planets: giant Jupiter takes only 10 hours to spin one day! Saturn, Uranus and Neptune are almost as fast. The longest-day award goes to Venus, which takes a really pokey 243 days to turn once relative to the Sun. In fact, Venus’ day is longer than its year! Venus takes only 224 of our days to go once around the Sun. So if you’re born on Venus, you get to celebrate your birthday every day!
Wee ones: All 8 planets are shaped like balls, or “spheres.” Do you see any ball shapes in the room around you?
Little kids: Uranus’ day is 17 hours long, while Neptune’s is 16 hours. Which one takes longer to spin once? Bonus: How much longer is the longer day?
Big kids: If at 7:00 pm tonight it’s noon somewhere on Neptune, at what Earth time will an alien on that spot have noon again? (Reminder: Neptune’s day takes 16 hours.) Bonus: Mercury’s day is 59 Earth-days long. If someone there has sunrise there today, on what day will he see the next sunrise? (Reminder if needed: July and August each have 31 days.)
The sky’s the limit: If someone sees sunrise on Venus today (July 28, 2020), in what Earth month will that person see sunrise next (243 Earth days from now)? Or feel free to figure out the exact day!
Wee ones: Different for everyone…look around your room!
Little kids: Uranus takes longer. Bonus: 1 hour longer.
Big kids: At 11:00 the next morning. Bonus: September 25, because Sept. 28 would be 62 days (31 + 31).
The sky’s the limit: Our months have about 30 days in them, so 243 days is about 8 months, which would be end of March 2021. It turns out to be exactly 8 months: Venus will end its “today” on March 28, 2021.
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.