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Space Time with Scott Mitchell

How many chickens away is the moon?

~Rebecca, Age 29, Costa Mesa


On its surface, this may seem like a pretty simple question, if not a little silly. I could easily say that the average chicken is about 40-50 cm (about 16-20 inches) tall and the average surface-to-surface distance to the Moon is 376,847 km (about 234162 mi), so you could fit approximately 837,437,778 chickens between the Earth and the Moon.


However, that doesn't address any of the real-life challenges of getting to the moon if you are restricted to chicken-based locomotion, but provides us with an opportunity to show just how mind-numbingly far apart things in space are.


While several breeds of chicken are capable of flight, this doesn't seem the most practical choice. Most chickens struggle to lift their own body weight, let alone you and all the life support equipment you'll need. On top of that, as you gain altitude the air gets thinner. You'll reach a point a couple miles up where no matter how many chickens you've tied together, their wings can't push enough air to generate the needed lift to keep from falling, even higher and eventually there will be so little air that without several thousand chicken-sized pressure suits, your poultry propulsion will start to suffocate.


So back to the idea of stacking chickens. I don't work with farm animals very often, but I have a very hardworst game of king-of-the-hill ever time putting any faith in their ability to balance a stack of more than 2 or 3 high, and certainly not over 800 million. Fortunately, there are an estimated 30 billion chickens living on earth, so we might have enough to shore up the base. In architecture there is a "slenderness ratio" that relates a tower's height to the width of its base. The tallest building in the world is the Burj Khalifa in Dubai with a ratio of 9:1, which means that at a height of 828 meters, the base is about 92 meters wide. There are buildings that push this ratio to a much more ridiculous 15:1 or even 24:1, but those barely reach half the height of the Burj Khalifa, and they are using building materials like steel and glass, which might be a little bit more sturdy than our stack of unruly chickens. We'll tell our chickens to hold onto each other tight and push our ratio to 10:1. This is a MASSIVE simplification, but I'm sure the chickens won't mind the sacrifice to make the math a little bit easier. At a slenderness ratio of 10:1, our 376,847 kilometer tower of chickens has a base diameter of 37,685 km, which, if circular, covers an area of about 1.1 Billion (with a B) square kilometers. This is about twice the surface area of the entire planet Earth if you rolled it out flat, and we're probably using more chickens in our tower than have ever lived in Earth's history. I won't go into the apocalyptic effects of having that many chickens so close to the Earth, but if you want to read about a similar hypothetical scenario that helped to inspire the style of this article, I highly recommend XKCD's What If.


You might be surprised to find out that securing the base of the lunar chicken tower isn't the only problem with our plan. It turns out the Earth rotates much faster than the moon orbits. Even if we were able to construct our tower, the chicken at the tip of it would be moving at just under 28,000 meters per second or around 62,630 miles per hour, and you'd have one chance per day to jump off the tower at the moon as it swung by. Since this speed is almost three times higher than Earth's escape velocity, if you miss your jump, you would be flung into space to orbit around the sun for the rest of your life. This honestly might be preferrable to being on-target, where you would really just be adding a new, small, slightly red crater to the Moon's Surface.


Another issue is that the moon's orbit isn't perfectly circular, and it's tilted with respect to Earth's equator where we built our chicken tower. The tilt means that the Moon can be up to 33,000 kilometers north or south of the tip of our tower when we swing by, and the eccentricity, a measure of how different the orbit is from a perfect circle, means that the actual distance to the Moon changes from 363,100 km at its closest, to 405,700 km at its furthest, a difference of over 40,000 km. So depending on our timing, even if we can line up with the Moon perfectly, our tower might be 48 million chickens too short, or get the top 48 million chickens knocked off.


Potentially the most fun problem with the tower though, is that at some point the direction we and our chickens are being pulled by gravity will switch. As we move on a straight line from the Earth to the Moon, Earth's gravity gets weaker and the Moon's gets stronger. Eventually we would reach a point where Earth's gravity and the Moon's gravity are exactly the same strength, but in opposite directions, meaning you can float there indefinitely, not falling one way or the other. Once you pass that point, called Lagrange Point L1, everything switches. Now the Earth is above you and the Moon below. You are no longer climbing up a tower of chickens; you, and all the chickens, are clinging to the tower above you trying not to fall the rest of the way to the Moon's surface. The L1 point is about 85% of the way from the Earth to the Moon, but that still means you'd need to descend 58,000 km. If you let go and surrender to freefall, you'll hit the surface at about 2340 meters per second, or 5234 miles per hour. Surviving would be no easy feat, especially since in the airless lunar environment, parachutes tend not to work.


The moral of the story is that using chickens to get to the moon would be a logistical nightmare, and I probably wouldn't pitch this to the NASA Artemis team.

 

Measurements and calculations made with WolframAlpha.
Mathematical errors made with not enough coffee.


If you have questions about the universe that you want answered in exhaustive detail like this extremely pointless but fun article, make sure to submit them here! Your question might be chosen for next month's Space Time w/ Scott Mitchell!

Not pictured: millions of splatted chickens