How Many Things Are There?

There aren't enough humans on Earth to fill the Grand Canyon, and in a lifetime you don't produce enough saliva to even fill a swimming pool. That suggests that most things around us are countable or measurable: so how many things are there?

That question is posed and -- kinda -- answered in this video by Vsauce. First, though, we need to answer an important question: what counts as a thing, anyway? Watch to find out. [YouTube]