Mathematics
The Curious Case of the Harmonic Series Divergence
Quick fact
If you could add one term every second, after 10^43 seconds (way longer than the age of the universe), the partial sum would still be less than 100.
Why this is interesting
You've probably learned that when you add smaller and smaller numbers, the sum settles down to a finite value. But what if the numbers shrink too slowly? Imagine adding 1 + 1/2 + 1/3 + 1/4 + ... forever—does this sum ever reach infinity?