Are there more wheels or more doors in the world? A simple question, with a not-so-simple answer (at least not yet.) Twitter user Ryan Nixon posed the question five days ago, and the internet is divided over it. 

The mind goes to cars first. Your average car is pretty 1:1 with four doors and four wheels. Homes and buildings, with all their doors inside and outside the buildings, might swing things in favor of doors -- but then again, what about all the door-less vehicles in the world? Scooters, skateboards, motorcycles etc. Heck, maybe it is wheels. 

But things get weirder. Thinking of all the door-less structures in the world -- how many homes and skyscrapers etc. -- it might seem obvious that it must be doors.

But, digging deeper, did you know a supermarket has more wheels than doors? Shopping carts. Elevators. Forklifts. Even the office this is being written in has nine doors -- and 234 wheels from the chairs alone

So, if you ask us, we're officially on Team Wheels. 

But the internet is fussing about it. It's a tough cookie to crack. And while the answer, at first, will seem obvious to you, the more people chime into the question the more confusing it becomes. There are some good points to be made for both sides.  

Indeed, what with all of the Hot Wheels and Tech Decks and Lego wheels floating around, do those count towards wheels? 

And here, Twitter user Jeff Meyer points to a larger question -- what defines a door? If you hold that valves are doors, each human heart has four valves. Multiply that by the total population and you have several dozen billion doors to add, excluding all the other valves present in nature. 

For the purposes of this debate, we would agree that aortic valves are a bit of a stretch by Team Doors, but it makes an important point: calculating whether there are more doors or more wheels in the world requires a clear definition of what constitutes a wheel or a door first.

We would argue, like EvidencedBasedFX up there, that doors should be portals for human movement with hinged barriers that rotate on a vertical axis. Hatches, trapdoors and empty doorways don't count. There's a case to be made for other varieties, such as sliding and rotating doors, as well. 

Wheels, a little trickier to define, we argue require an axle. The wheel was a useless invention until someone figured out that drilling a hole through the center and putting a stick through it was like, really good. It should also be used in the movement of something across a plane -- this includes things like the wheels in drawers or even a rolling pin (if it's of the two-piece axle variety). 

Seriously, thinking about it, is there any reliable way to find the answer to the question? What makes an object what it is -- is a wheel because of its shape or because of its function? Is a bottle of hand sanitizer a wheel if it's used as one? Does a wheel become a chair if you're sitting on it? It's an interesting question, and one the internet will likely be divided over for some time to come.