Appreciation post: My brother showed me a simple experiment with a ball and a shadow

I used to be dead set on the flat earth idea, but my brother Dave suggested we go outside with a basketball and a flashlight. We set the ball on a stick in the yard and moved the light around it. The shadow on the ball matched what you'd see during a lunar eclipse, with a curved edge. That test took about 10 minutes and it made me wonder what else I could check myself. Has anyone else tried a hands-on experiment that shifted their view?

3 comments

3 Comments

aaronsullivan29d agoMost Upvoted

Man, that basketball and flashlight trick is exactly what got me too! I did the same thing with a soccer ball and a work lamp, and it just clicked immediately how light curves around a sphere.

the_rowan1mo ago

Grabbed a frisbee and a lamp one night after watching some sky videos. I held the frisbee up at different angles to see how the light from the lamp hit it, trying to recreate what the moon does. The dark part of the frisbee was ALWAYS curved, no matter how I twisted it. It got me thinking about how we see shadows on the moon and what that really means for how light works in space.

felix4141mo ago

Honestly, this is one of those things where I used to think the shadows on the moon were just from the sun hitting it wrong or something. But after messing around with a flashlight and a ball in my backyard, I totally get what you mean. The curved shadow on the frisbee makes total sense when you see how light wraps around a sphere in space. Your mile may vary, but that little experiment you did really changed how I see the moon phases now.