WThey all have those thoughts that come to us in the wee hours of the night. Who am I? Why are we here? What if my mobile ran on vacuum tubes instead? Randall Munroe has collected the answers to, well, just one of those questions, as well as the answers to a whole host of others in What if? 2: Additional Serious Scientific Answers to Absurd Hypothetical Questions. Yes, that’s a T-Rex eating a plane. In the excerpt below, Munroe explores what it takes to drag an average-sized human in a chair over Australia’s tallest skyscraper, using only the power of pigeons. a lot and a lot of pigeons.
taken from What if? 2 by Randall Munroe. Copyright © 2022 by Randall Munroe. Extracted with permission from Riverhead, an imprint and division of Penguin Random House LLC, New York. All rights reserved. No part of this excerpt may be reproduced or reprinted without the written permission of the publisher.
How many pigeons would it take to lift the average person and a launch chair to the height of Australia’s Q1 skyscraper?
In a 2013 study, researchers at the Nanjing University of Aeronautics and Astronautics led by Ting Ting Liu trained pigeons to fly to a perch while wearing weighted armor. They found that the average pigeon in their study could take off and fly up while carrying 124 grams, about 25 percent of its body weight.
The researchers found that the pigeons could fly better if the weights were hung under their bodies, rather than on their backs, so you would probably want pigeons to lift your seat from above rather than support it from below.
Let’s say your chair and harness weigh 5 pounds and you weigh 65 pounds. If you were to use the pigeons from the 2013 study, it would take a flock of about 600 to lift your chair and fly with it.
Unfortunately flying with a load is a lot of work. The pigeons in the 2013 study could carry a load 1.4 meters up to a perch, but they probably couldn’t have flown much higher than that. Even unencumbered pigeons can sustain a strenuous vertical flight for just a few seconds. A 1965 study measured a climbing speed of 2.5 m/s for unencumbered pigeons,* so even if we are optimistic it seems unlikely that pigeons can lift your chair more than 5 meters.I
No problem, you might think. If 600 pigeons can lift you the first 5 meters, then you just have to bring 600 more, like the second stage of a rocket, to carry you the next 5 meters when the first swarm gets tired. After that you can take another 600 for the 5 meters and so on. The Q1 is 322 meters high, so about 40,000 pigeons should be able to get you to the top, right?
No. There is a problem with this idea.
Since a pigeon can only carry a quarter of its body weight, it takes four flying pigeons to carry one resting pigeon. That means that each “stage” needs at least four times as many pigeons as the one above. Lifting one person can only take 600 pigeons, but lifting one person and 600 resting pigeons would take another 3,000 pigeons.
This exponential growth means that a 9-stage vehicle that you can lift 45 meters requires almost 300 million pigeons, roughly equivalent to the entire world population. Reaching the halfway mark would require 1.6 × 1025 pigeons, which would weigh about 8 × 1024 kilograms – more than the Earth itself. At that point, the pigeons wouldn’t be pulled down by the Earth’s gravity – the Earth would be pulled up by the pigeons’ gravity.
The entire 65-stage craft to reach the top of the Q1 would weigh 3.5 × 1046 kilograms. That’s not just more pigeons than there are on Earth, it’s more mass than there is in the galaxy.
You could make it more efficient by reusing pigeons. In the 2013 study, the researchers gave the pigeons 30 seconds to rest on the perch before lowering them for another trial. If each “stage” lasts two seconds and pigeons are refreshed after 30 seconds, you could fly arbitrarily high with a 15-stage craft – but that would still require trillions of pigeons.
A better approach might be not to drag the pigeons along. After all, pigeons can climb to the top of the skyscraper on their own, so you might as well send them ahead to wait there rather than have their friends carry them with you. If you could train them well enough, you could slide them to the correct height, then grab hold of you and pull you up for a few seconds when you reach their height. Keep in mind that pigeons can’t grab and carry things with their feet, so they need small, aircraft carrier-style hooked harnesses to intercept you.
With this setup it is possible that you fly to the top of the tower yourself with a few tens of thousands of well-trained pigeons. You should probably make sure you have some sort of safety system in place that makes sure you don’t go down every time a falcon flies by and scares the pigeons.
Not only would the craft be more dangerous than an elevator, it would also be a lot harder to pick your destination. You could plan to get to the top of Q1, but once you’ve gone… you’re completely under the control of anyone with a bag of seeds.
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