What Is Sea Level, Anyway?

In Calipatria, California, the town is below sea level -- but their flag pole isn't. But what does "sea level" mean? Is it just theory, or is there more behind it?

🟥 MORE FROM TOM: https://www.tomscott.com/
(you can find contact details and social links there too)

📰 WEEKLY NEWSLETTER with good stuff from the rest of the internet: https://www.tomscott.com/newsletter/
❓ LATERAL, free weekly podcast: https://lateralcast.com/ https://youtube.com/lateralcast/
➕ TOM SCOTT PLUS: https://youtube.com/tomscottplus
👥 THE TECHNICAL DIFFICULTIES: https://youtube.com/techdif