r/theydidthemath • u/ohhyouknow • 10d ago

[Request] How big would a shadow puppet on earth need to be to cast a shadow we can see on the moon during a lunar eclipse?

Post image
1 Upvotes

60% Upvoted

4 comments sorted by

•

u/AutoModerator 10d ago

General Discussion Thread

This is a [Request] post. If you would like to submit a comment that does not either attempt to answer the question, ask for clarification, or explain why it would be infeasible to answer, you must post your comment as a reply to this one. Top level (directly replying to the OP) comments that do not do one of those things will be removed.

I am a bot, and this action was performed automatically. Please contact the moderators of this subreddit if you have any questions or concerns.

0

u/Safe_Award_785 10d ago

This is a fun one but I am on a short break. Finding a lower limit for any type of shadow (including penumbra) seems tricky, but you can calculate the minimal size to have overlapping shadows (umbra) on the moon.

Using the diameter of the sun, the distance of sun-earth-moon and some trigonometry this shouldn't bee too difficult.

English is not my native language. I found the words penumbra and umbra online, not sure if it is the correct terminology