Tuesday, April 12, 2016

Pizza Bird: Funny

My boyfriend recently took a flight on a plane with wifi, and while he was up there, wistfully asked if I could send him a pizza. I jokingly sent him a photo of a parrot holding a pizza slice in its beak. Obviously, my boyfriend had to go without pizza until he landed at JFK. But this raised the question: could a bird deliver a standard 20" New York-style cheese pizza in a box? And if so, what kind of bird would it take?

—Tina Nguyen

A bird could, possibly, deliver a pizza to a house. Delivering it to an airliner is a lot harder.

A 20-inch pizza weighs about 1.8 kg.[1] That's about 100 times the weight of a sparrow, so we're definitely going to need a large bird. There are all sorts of birds bigger than our pizza, including eagles, swans, cranes, pelicans, and albatrosses. However, some of them would do better at pizza delivery than others. To see why, let's take a look at wing shapes.

Birds have different types of wings depending on what kind of flying they need to do. Of all the types of wings, the ones best suited for pizza delivery are probably the relatively short-and-broad kind found on many soaring hawks and eagles.[2]​[3]These wings are good for taking off while carrying a heavy load, which is of course necessary for pizza delivery.

The largest birds of prey in North America[4] are the bald eagles[5] and golden eagles, which weigh about 4 or 5 kilograms when fully grown. The famous viral video of a golden eagle snatching a toddler is fake, but eagles have been seen to lift some awfully heavy things. Last year, photographer Alex Lamine saw a bald eagle in Georgia carrying a 12-pound (5.4 kg) tree branch, presumably to add to its gigantic nest. The eagle dropped the branch before making it back to the nest, but it definitely proved the bird was capable of flying—at least briefly—while carrying a load equal to its own body weight.

As a general rule, though, birds of prey won't try to pick up more than about half of their own weight. This means a half-kilogram peregrine falcon[6] couldn't pick up our 2-kilogram pizza. A 5-kilogram eagle, on the other hand, probably could.

However, picking up a pizza is one thing, but what about delivering it to an airliner?

Soaring birds like vultures—and eagles—can ride thermals[7] to extreme heights. In tropical regions, where the sunlight-powered thermals are strongest, planes have encountered[8] soaring Rüppell's vultures at altitudes of over 10 kilometers. That's high enough to reach a cruising airliner—but, unfortunately, this kind of soaring flight requires ideal flying conditions. "Having a pizza strapped to you" is definitely not that.

So a bird could potentially carry a pizza, but it couldn't fly up to an airliner with it. That's just as well, because there's one more major problem you'd face: Speed.

Whether or not a bird can fly as high as an airliner, it definitely can't fly as fast. Even if the person in the plane managed to get the emergency door open, they'd have to find a way to grab the pizza.

If you tip a pizza box too far, the cheese runs off one side. This critical angle varies from pizza to pizza and depends greatly on temperature, but let's suppose it's about 45°. That angle tells us that a pizza can handle a maximum sideways acceleration of about 1g.[9] To accelerate up to an airliner cruising speed of 500 mph, we'll need the acceleration to happen over a distance of over a mile. In other words, we'd need a mile-long mechanism trailing behind the plane to gently reel in the pizza.

But wait—those calculations assume sideways acceleration. Pizzas—like humans—handle "face-first" acceleration best. If the pizza were rotated during the handoff, it could survive a much greater acceleration, allowing the grabbing mechanism to be smaller.

What kind of face-first acceleration can a pizza survive before it spreads out to fill the bottom of the box? I haven't found any data on that, but if anyone wants to try to sneak a pizza into a centrifuge, go for it. Be sure to take pictures!

All in all, if you're in a plane and feel the urge to order a pizza, it's probably easier to just wait until you land. Then, if you really want, you can try to get a bird to deliver it.

But don't be surprised if some slices go missing along the way.