The great Marion Alteri, our local horse racing expert (see her blog: Marizy Doats), brings us this week’s question. What is the average air speed velocity of a laden swallow? To this I say: Ha-ha. Very funny.
If you don’t get the joke, it’s a reference to the movie Monty Python’s: The Holy Grail. They need to cross a bridge to continue their quest but in order to do so, they have to answer the above question. If you haven’t seen it, click here to see the clip from the movie. I also recommend the completely unrelated skit Monty Python’s Flying Circus – Frontiers in Medicine… it’s my favorite.
Now, as you’ve seen in the movie (or in the clip I linked above) I could shoot back with, “What do you mean, an African or European Swallow?” and call it a day, but I’m going to take the high road. Hopefully, my answer will get us all across the bridge… even if it’s in a less than funny manner.
This was certainly a tricky question to say the least. Lots of physics involved that I have pushed to those dusty corners in my mind. Not to mention you need to know a little bit about swallows.
Leave it to Marion to make me think this hard…
Let’s start with what an unladen swallow is. The simple answer, it’s a bird. The more complicated answer is that it’s a bird with 74 distinct species of swallow. Some found in Africa, others in Europe.
What is air speed velocity? It’s the relative velocity between some object, in this case the swallow, and the air.
In order to calculate the airspeed you have to take the difference between ground speed and the wind speed. Ground speed is the speed in which an object moves relative to some reference point on the ground. Wind speed is the speed in which the air moves relative to some reference point on the ground.
If there was a case in which a day had absolutely no wind, the ground speed is equal to the wind speed. Of course this is highly unlikely to ever happen.
This definition applies best to planes. When dealing with animals is a little different. To find the airspeed velocity of a bird, one must calculate the Strouhal number. The Strouhal number is usually used in the calculation of speed of fish in water. In that case, it is the ratio of frequency of the tail moving and the forward speed of the animal. A man named Graham K. Taylor discovered the same principle can be applied to birds and other animals that can fly.
For birds, the Strouhal number is the frequency multiplied by the amplitude of the wings divided by the animal’s speed through the air. The frequency is the number of times the bird beats its wings a second and the amplitude is the distance the wing travels in one beat.
To get an approximate airspeed, Taylor said to invert the midpoint Strouhal number (which is 0.3). This means that the airspeed about 3 times the product of the frequency and the amplitude.
There is a very detailed blog on style.org that discusses all the fun mathematical details of the Strouhal Number if you are interested. Here’s a link: The Strouhal Number in Cruising Flight
Now, in the case of the swallow, the Strouhal number is actually less than the average so it doesn’t work right out of the box. For all the details, see: Estimating the Airspeed Velocity of an Unladen Swallow
In the end, it’s concluded that the airspeed velocity of a (European) unladen swallow is about 24 miles per hour or 11 meters per second.
But, the real question is not about swallows at all. King Arthur in the movie had two coconut shells that he banged together to simulate the sound of a horse galloping. No one seems to know where he got them. So, the real question is how did the coconut get to medieval England? Is it possible that a swallow carried it over?
Well, I’m never one to make the claim that something is impossible. However, the swallow would have a very hard time even carrying the smallest of coconuts. It’s little wings would have to beat extremely fast and it would have to be able to fly for a very long time without a break. And if the swallow carried over a seed, the coconut tree probably wouldn’t survive very long as it thrives in tropical weather.
it is a lot more likely that coconuts were brought over by the
Portuguese from India in the 16th century. Another possibility is that
they “floated” through the ocean from India or possibly Australia to
England and were discovered around that time.
Now, the legend of King Arthur takes place in about the 12th century and evidence suggests coconuts did not get to England until the 16th century (as I just stated).
So, there is a very distinct possibility that the whole thing is just a mistake on the part the writers of Monty Python.
On second thought, I think it’s just what they do. It’s a comedy and there is a recurring theme throughout the whole movie trying to figure out where the coconuts came from. It doesn’t have to make sense. It’s just funny to think about… I’m sure historical accuracy wasn’t exactly their concern…