It's a question that has vexed many a genius in physics, including Isaac Newton. Even lesser minds like you and me would like to know the answer: Do we swim slower in syrup than in water? I can now tell you, authoritatively, the answer: No, it makes almost no difference. In a physics experiment that sounded more like a prank, Edward Cussler of the University of Minnesota and his student Brian Gettelfinger dumped 300kg of guar gum, a thickening agent used in ice cream and salad dressings, into a 25-metre-long campus swimming pool and then found 16 volunteers to swim in the goo, which was twice as thick as water. 'It looked like snot,' Professor Cussler told Nature, the science weekly. The pranksters-cum-scientists found that whatever strokes they used, the swimmers' times differed by zero to less than 4 per cent from their performance in normal pool water. Instead of being expelled from school, the pair have become campus celebrities. Their findings have been published in the American Institute of Chemistry and Engineering Journal. The problem has troubled physicists since Newton, who believed an object's speed through a fluid depends on the fluid's viscosity, whereas his contemporary Christian Huygens thought otherwise. Huygens was right, says Professor Cussler, because although swimmers experience more friction in thickened water, they also generate more forward force from every stroke, so the opposing forces cancel out.