If you were born on April 4, 2007, you’re already 15 years old. A wild idea, right? Christiaan Huygens, Rembrandt van Rijn, Freek Vonk, and Mark Rutte. What are the similarities between these men? Besides the fact that all four of them are Dutch, they are all alumni of Leiden University. Huffing and puffing, teachers today cycle through the city to give guest lessons at schools. Are you 15 and living in Leiden? You might even get to see or speak to them. They won't bite, probably…