It’s a lot more than three.
It was little more than a brilliant piece of 1970s TV marketing, but Tootsie Pops’ eternal question — how many licks does it take to get to the Tootsie Roll center of a Tootsie Pop? — is one that always demanded an answer, probably because it was easy to test yourself.
There have already been a few scientific studies of just how many licks it would take, using licking machines and human testers, but a new paper in the Journal of Fluid Mechanics has the most detailed analysis yet.
Jinzi Mac Huang, M. Nicholas J. Moore and Leif Ristroph used hard candy in their paper to model how quickly moving fluids can dissolve various surfaces. This kind of destruction is hard to accurately model, however, because some of the dissolved material interacts with the fluid and the surface is constantly changing as it dissolves. Nevertheless, Huang and colleagues were able to produce a mathematical model that could predict the final geometry of a piece of hard candy dissolving in moving fluid.
“As a whimsical application,” the team ends the paper, “this scaling allows us to address the following long-standing question: ‘How many licks does it take to get to the centre of a lollipop?'” Based on their model, it will take about 1,000 licks to get through a centimeter of candy.
A Tootsie Pop has a diameter of over 2.5 centimeters, so the model predicts at least 2,500 licks to get to the center.
The world now totally knows.