WEBVTT 99:59:59.999 --> 99:59:59.999 French fries are delicious. 99:59:59.999 --> 99:59:59.999 French fries with ketchup are a little slice of heaven. 99:59:59.999 --> 99:59:59.999 The problem is it's basically impossible 99:59:59.999 --> 99:59:59.999 to pour the exactly right amount. 99:59:59.999 --> 99:59:59.999 We're so used to pouring ketchup that we don't realize 99:59:59.999 --> 99:59:59.999 how weird its behavior is. 99:59:59.999 --> 99:59:59.999 Imagine a ketchup bottle filled with a straight up solid like steel. 99:59:59.999 --> 99:59:59.999 No amount of shaking would ever get the steel out. 99:59:59.999 --> 99:59:59.999 Now imagine that same bottle full of a liquid like water. 99:59:59.999 --> 99:59:59.999 That would pour like a dream. 99:59:59.999 --> 99:59:59.999 Ketchup, though, can't seem to make up its mind. 99:59:59.999 --> 99:59:59.999 Is it is a solid? Or a liquid? 99:59:59.999 --> 99:59:59.999 The answer is, it depends. 99:59:59.999 --> 99:59:59.999 The world's most common liquids like water, oils and alcohols 99:59:59.999 --> 99:59:59.999 respond to force linearly. 99:59:59.999 --> 99:59:59.999 If you push on them twice as hard, they move twice as fast. 99:59:59.999 --> 99:59:59.999 Sir Isaac Newton, of apple fame, first proposed this relationship, 99:59:59.999 --> 99:59:59.999 and so those fluids are called Newtonian fluids. 99:59:59.999 --> 99:59:59.999 Ketchup, though, is part of a merry band of linear rule breakers 99:59:59.999 --> 99:59:59.999 called Non-Newtonian fluids. 99:59:59.999 --> 99:59:59.999 Mayonnaise, toothpaste, blood, pain, peanut butter 99:59:59.999 --> 99:59:59.999 and lots of other fluids respond to force non-linearly. 99:59:59.999 --> 99:59:59.999 That is, their apparent thickness changes 99:59:59.999 --> 99:59:59.999 depending on how hard you push, or how long, or how fast. 99:59:59.999 --> 99:59:59.999 And ketchup is actually Non-Newtonian in two different ways. 99:59:59.999 --> 99:59:59.999 Way number one: the harder you push, the thinner ketchup seems to get. 99:59:59.999 --> 99:59:59.999 Below a certain pushing force, 99:59:59.999 --> 99:59:59.999 ketchup basically behaves like a solid. 99:59:59.999 --> 99:59:59.999 But once you pass that breaking point, 99:59:59.999 --> 99:59:59.999 it switches gears and becomes a thousand times thinner than it was before. 99:59:59.999 --> 99:59:59.999 Sound familiar right? 99:59:59.999 --> 99:59:59.999 Way number two: if you push with a force below the threshold force 99:59:59.999 --> 99:59:59.999 eventually, the ketchup will start to flow. 99:59:59.999 --> 99:59:59.999 In this case, time, not force, is they key to releasing ketchup 99:59:59.999 --> 99:59:59.999 from its glassy prison. 99:59:59.999 --> 99:59:59.999 Alright, so, why does ketchup act all weird? 99:59:59.999 --> 99:59:59.999 Well, it's made from tomatoes, pulverized, smashed, thrashed 99:59:59.999 --> 99:59:59.999 utterly destroyed tomatoes. 99:59:59.999 --> 99:59:59.999 See these tiny particles? 99:59:59.999 --> 99:59:59.999 This is what remains of tomatoes 99:59:59.999 --> 99:59:59.999 after they go through the ketchup treatment. 99:59:59.999 --> 99:59:59.999 And the liquid around those particles? 99:59:59.999 --> 99:59:59.999 That's mostly water and some vinegar, sugar, and spices. 99:59:59.999 --> 99:59:59.999 When ketchup is just sitting around, 99:59:59.999 --> 99:59:59.999 the tomato particles are evenly and randomly distributed. 99:59:59.999 --> 99:59:59.999 Now, let's say you apply a week force very quickly. 99:59:59.999 --> 99:59:59.999 The particles bump into each other, 99:59:59.999 --> 99:59:59.999 but can't get out of each other's way, 99:59:59.999 --> 99:59:59.999 so the ketchup doesn't flow. 99:59:59.999 --> 99:59:59.999 Now, let's say you apply a strong force very quickly. 99:59:59.999 --> 99:59:59.999 That extra force is enough to squish the tomato particles, 99:59:59.999 --> 99:59:59.999 so maybe instead of little spheres, 99:59:59.999 --> 99:59:59.999 they get smushed into little ellipses, and boom! 99:59:59.999 --> 99:59:59.999 Now you have enough space for one group of particles 99:59:59.999 --> 99:59:59.999 to get passed others and the ketchup flows. 99:59:59.999 --> 99:59:59.999 Now let's say you apply a very weak force for a very long time. 99:59:59.999 --> 99:59:59.999 Turns out, we're not exactly sure what happens in this scenario. 99:59:59.999 --> 99:59:59.999 One possibility is that the tomato particles near the walls of the container 99:59:59.999 --> 99:59:59.999 slowly get bumped towards the middle, 99:59:59.999 --> 99:59:59.999 leaving the soup they were dissolved in, 99:59:59.999 --> 99:59:59.999 which remember is basically water, 99:59:59.999 --> 99:59:59.999 near the edges. 99:59:59.999 --> 99:59:59.999 That water serves as a lubricant betwen the glass bottle 99:59:59.999 --> 99:59:59.999 and the center plug of ketchup, 99:59:59.999 --> 99:59:59.999 and so the ketchup flows. 99:59:59.999 --> 99:59:59.999 Another possibility is that the particles slowly rearrange themselves 99:59:59.999 --> 99:59:59.999 into lots of small groups, which then flow past each other. 99:59:59.999 --> 99:59:59.999 Scientists who study fluid flows are still actively researching 99:59:59.999 --> 99:59:59.999 how ketchup and its merry friends work. 99:59:59.999 --> 99:59:59.999 Ketchup basically gets thinner the harder you push, 99:59:59.999 --> 99:59:59.999 but other substances like oobleck or some natural peanut butters 99:59:59.999 --> 99:59:59.999 actually get thicker the harder you push. 99:59:59.999 --> 99:59:59.999 Others can climb up rotating rods, 99:59:59.999 --> 99:59:59.999 or continue to pour themselves out of a beeker, 99:59:59.999 --> 99:59:59.999 once you get them started. 99:59:59.999 --> 99:59:59.999 From a physics perspective, though, 99:59:59.999 --> 99:59:59.999 ketchup is one of the more complicated mixtures out there. 99:59:59.999 --> 99:59:59.999 And as if that weren't enough, the balance of ingredients 99:59:59.999 --> 99:59:59.999 and the presence of natural thickeners like xanthan gum, 99:59:59.999 --> 99:59:59.999 which is also found in many fruit drinks and milkshakes, 99:59:59.999 --> 99:59:59.999 can mean that two different ketchups 99:59:59.999 --> 99:59:59.999 can behave completely differently. 99:59:59.999 --> 99:59:59.999 But most will show two telltale properties: 99:59:59.999 --> 99:59:59.999 sudden thinning at a threshold force, 99:59:59.999 --> 99:59:59.999 and more gradual thinning after a small force 99:59:59.999 --> 99:59:59.999 is applied for a long time. 99:59:59.999 --> 99:59:59.999 And that means you could get ketchup out of the bottle in two ways. 99:59:59.999 --> 99:59:59.999 Either give it a series of long, slow languid shakes 99:59:59.999 --> 99:59:59.999 making sure you don't ever stop applying force, 99:59:59.999 --> 99:59:59.999 or you could hit the bottle once very, very hard. 99:59:59.999 --> 99:59:59.999 What the real pros do is keep the lid on, 99:59:59.999 --> 99:59:59.999 give the bottle a few short, sharp shakes 99:59:59.999 --> 99:59:59.999 to wake up all those tomato particles, 99:59:59.999 --> 99:59:59.999 and then take the lid off 99:59:59.999 --> 99:59:59.999 and do a nice controlled pour onto their heavenly fries. 99:59:59.999 --> 99:59:59.999