Why Does Infinity Feel So Big?

Imagine you have a bag of marbles. If there are just a few, it’s easy to count them all. But if the bag has an infinite number of marbles, like never ending, how do you even begin counting? It turns out, some infinite collections can be bigger than others, like having two endless bags, one with marbles and one with both marbles and jellybeans. Surprisingly, they might not all be the same size!