In the world of Harry Potter the young wizard undergoes two magical biological transformations: eating Gillyweed to grow gills in order to breathe underwater and drinking Skele-Gro to repair broken bones.
Natural Sciences students from the University of Leicester have put these arcane medical practices to the test — and have concluded that a little magic might indeed be required in both situations to make them scientifically feasible.
The research is revealed just before Harry Potter and the Cursed Child opens as a West End stage play in London and Fantastic Beasts and Where to Find Them is released in cinemas worldwide.
Gillyweed — Drowning with Gills?
In Harry Potter and the Goblet of Fire, Harry passes the second Triwizard task by consuming Gillyweed, which allows him to breathe underwater by causing gills to grow on his neck.
To check the feasibility of Harry surviving with home-grown gills, in a paper for the Journal for Interdisciplinary Science Topics, students Rowan Reynolds and Chris Ringrose first inspected the gills themselves, estimating them to be approximately 60cm2 in surface area based on their appearance in the film.
Taking into account the oxygen content of the Black Lake and the maximum oxygen use of swimming, they then examined Harry’s weight, suggesting that if he had a normal BMI — providing he hadn’t been binging too much on Every Flavour Beans and Chocolate Frogs — and the average height of a 14 year old boy, he would need to process 443 litres of water at 100% efficiency per minute for every minute he was underwater.
This would mean the water would have to flow at 2.46 metres per second — twice the velocity of normal airflow and therefore far faster than he could inhale and exhale, causing him to suffocate.
Interestingly, Harry is seen swimming with his mouth closed, which is not how gills work — the students suggest that if Harry were to open his mouth to allow water into his throat and out through the gills, it may be plausible he could breathe underwater. By keeping his mouth shut, however, he would not be able to extract sufficient oxygen for survival, and as a result would lose his title as ‘The Boy Who Lived’ quite quickly after suffocating.
