Monty Python and the Holy Grail still continues to amuse today. For fans, one question from the movie often provokes discussion - what is the airspeed of an unladen swallow?
This question was originally posed on the Bridge of Death by the troll who guards it. If visitors answered any question given to them correctly, they were allowed to pass. If they didn't know the answer, then they were plunged into the pit below.
If you are having trouble remembering, be sure to watch the short clip above of the comedic scene. In the same scene, the question is posed of whether this refers to an African or a European swallow. We'll have to take this into account when we do our math later, too.
The discussion also includes the question of how two halves of a coconut ended up in Europe, with the proposition that a swallow carried a coconut from the tropics. Take a look at the clip below to refresh your memory of that.
With the amusing background out of the way, let’s calculate the airspeed of an unladen swallow, and determine whether said swallow would in fact able to carry a coconut to Europe, to be used to create fake horse sounds for King Arthur.
Calculating the airspeed of the swallow
First, we need to determine which bird to examine as best fits for those discussed in the movie. There is, in fact, a European swallow, but there is no swallow specifically named the African Swallow. However, there is a South African swallow and a West African swallow, which may be good fits when discussing an African swallow. However, there is almost no data recorded that can give us an indication of the airspeed of either type of African swallow. Rather than make blind guesses about African swallow, it may be better to look into the capabilities of the European, or Barn, swallow, for which there is.
According to research from the Avian Demography Unit of the University of Capetown, the European swallow has an average length of 12.2 cm and an average mass of about 20 grams. If we use the information mentioned in the videos above, we would estimate that a European swallow flaps its wings 43 times every second in order to maintain the necessary airspeed velocity.
Examining research by zoologist C. J. Pennycuick, in a journal article entitled Predicting Wingbeat Frequency and Wavelength of Birds, we can find relevant data to the European swallow. While the European swallow wasn’t specifically examined in his study, a swallow of the same average weight was. This 20-gram swallow was found to flap its wings about 12 times every second, with an amplitude of 20 cm each time. Strike one for Monty Python. Though, I guess we can give them a little bit of credit here, considering that the swallow being observed in this research wasn't exactly what King Arthur was talking about.
Now that we have the number of beats per second of the swallow’s wings, and the amplitude, we can begin estimating the airspeed. Each beat of the swallow’s wings carries it some distance forward. There is no way to know exactly how far the average European swallow’s wing flap propels it, but we can estimate about .75 meters per beat, according to various studies. When we take the number of beats per second (12) and multiply it by the distance per beat (.75), we get a value for the velocity of 9 meters per second. Translating this into miles per hour, we see that the airspeed velocity of a European swallow is 20.1 mph. This number lines up with the measured velocities of real birds as well, which means we're on the right track for the mathematics.
So, answering the main question here, the airspeed velocity of an unladen swallow is something like 20.1 miles per hour or 9 meters per second. But, what if the swallow was laden by, say, carrying a coconut to Europe?
Could the swallow carry a coconut?
Now that we understand the bird's possible airspeed, let’s assume that, theoretically, a European swallow could find a coconut in its normal habitat. Would it even then be possible for a swallow weighing 20 grams to pick up a coconut and transport it to Europe?
Assuming a large coconut, as seen in the video, this is a fairly absurd proposition. There's no way that a bird as small as a swallow could carry a coconut that was more than double its weight. However, there may be a way that we can make the math work here.
Since we’re already dealing with an absurd scenario, let’s imagine that the swallow found the world’s smallest coconut ever recorded, weighing in at 3.847 grams, according to the India Book of Records. So then, the question becomes, can a 20-gram swallow carry a 3.387-gram coconut?
A 20-gram swallow carrying a coconut just one-fifth of its weight seems more probable than a 20-gram swallow carrying a coconut twice its weight. However, a lot would have to line up to make this unlikely scenario happen. As extremely unlikely as it is, however, the story told in Monty Python and the Holy Grail may just be possible.
Despite the incredible improbability of the scenario, it would theoretically be possible for a large European swallow to somehow come across an incredibly small coconut and carry it to the destination where King Arthur would have found it. As it turns out, Monty Python has a little bit of truth in it, but only just barely.
Chances are there are a few other angles to this problem as well. If anyone out there who lives in Europe wants to find a swallow and measure its airspeed with absolute certainty, we could probably answer the original question more accurately. Even better, if anyone out there wants to train a swallow to carry a small coconut, you likely would have a viral video on your hands.