0:00:06.226,0:00:08.741 French fries are delicious. 0:00:08.741,0:00:12.437 French fries with ketchup are a little slice of heaven. 0:00:12.437,0:00:15.476 The problem is it's basically impossible 0:00:15.476,0:00:17.914 to pour the exactly right amount. 0:00:17.914,0:00:20.044 We're so used to pouring ketchup that we don't realize 0:00:20.044,0:00:22.555 how weird its behavior is. 0:00:22.555,0:00:25.876 Imagine a ketchup bottle filled with a straight up solid like steel. 0:00:25.876,0:00:29.528 No amount of shaking would ever get the steel out. 0:00:29.528,0:00:32.740 Now imagine that same bottle full of a liquid like water. 0:00:32.740,0:00:34.539 That would pour like a dream. 0:00:34.539,0:00:37.044 Ketchup, though, can't seem to make up its mind. 0:00:37.044,0:00:38.907 Is it is a solid? Or a liquid? 0:00:38.907,0:00:41.738 The answer is, it depends. 0:00:41.738,0:00:45.044 The world's most common liquids like water, oils and alcohols 0:00:45.044,0:00:47.772 respond to force linearly. 0:00:47.772,0:00:51.139 If you push on them twice as hard, they move twice as fast. 0:00:51.139,0:00:54.603 Sir Isaac Newton, of apple fame, first proposed this relationship, 0:00:54.603,0:00:57.958 and so those fluids are called Newtonian fluids. 0:00:57.958,0:01:00.676 Ketchup, though, is part of a merry band of linear rule breakers 0:01:00.676,0:01:03.307 called Non-Newtonian fluids. 0:01:03.307,0:01:05.876 Mayonnaise, toothpaste, blood, pain, peanut butter 0:01:05.876,0:01:10.077 and lots of other fluids respond to force non-linearly. 0:01:10.077,0:01:12.006 That is, their apparent thickness changes 0:01:12.006,0:01:15.275 depending on how hard you push, or how long, or how fast. 0:01:15.275,0:01:18.707 And ketchup is actually Non-Newtonian in two different ways. 0:01:18.707,0:01:23.172 Way number one: the harder you push, the thinner ketchup seems to get. 0:01:23.172,0:01:24.677 Below a certain pushing force, 0:01:24.677,0:01:27.150 ketchup basically behaves like a solid. 0:01:27.150,0:01:29.245 But once you pass that breaking point, 0:01:29.245,0:01:33.644 it switches gears and becomes a thousand times thinner than it was before. 0:01:33.644,0:01:35.636 Sound familiar right? 0:01:35.636,0:01:39.475 Way number two: if you push with a force below the threshold force 0:01:39.475,0:01:41.771 eventually, the ketchup will start to flow. 0:01:41.771,0:01:45.340 In this case, time, not force, is they key to releasing ketchup 0:01:45.340,0:01:47.444 from its glassy prison. 0:01:47.444,0:01:49.372 Alright, so, why does ketchup act all weird? 0:01:49.372,0:01:52.801 Well, it's made from tomatoes, pulverized, smashed, thrashed 0:01:52.801,0:01:55.509 utterly destroyed tomatoes. 0:01:55.509,0:01:56.915 See these tiny particles? 0:01:56.915,0:01:58.403 This is what remains of tomatoes cells 0:01:58.403,0:01:59.909 after they go through the ketchup treatment. 0:02:01.016,0:02:03.253 And the liquid around those particles? 0:02:03.253,0:02:06.718 That's mostly water and some vinegar, sugar, and spices. 0:02:06.718,0:02:08.314 When ketchup is just sitting around, 0:02:08.314,0:02:11.793 the tomato particles are evenly and randomly distributed. 0:02:11.793,0:02:14.176 Now, let's say you apply a week force very quickly. 0:02:14.176,0:02:15.684 The particles bump into each other, 0:02:15.684,0:02:17.483 but can't get out of each other's way, 0:02:17.483,0:02:18.977 so the ketchup doesn't flow. 0:02:18.977,0:02:21.985 Now, let's say you apply a strong force very quickly. 0:02:21.985,0:02:24.849 That extra force is enough to squish the tomato particles, 0:02:24.849,0:02:26.156 so maybe instead of little spheres, 0:02:26.156,0:02:29.012 they get smushed into little ellipses, and boom! 0:02:29.012,0:02:31.145 Now you have enough space for one group of particles 0:02:31.145,0:02:34.406 to get passed others and the ketchup flows. 0:02:34.406,0:02:37.900 Now let's say you apply a very weak force but for a very long time. 0:02:38.435,0:02:41.500 Turns out, we're not exactly sure what happens in this scenario. 0:02:41.500,0:02:45.210 One possibility is that the tomato particles near the walls of the container 0:02:45.210,0:02:47.499 slowly get bumped towards the middle, 0:02:47.499,0:02:49.099 leaving the soup they were dissolved in, 0:02:49.099,0:02:50.667 which remember is basically water, 0:02:50.667,0:02:51.938 near the edges. 0:02:51.938,0:02:54.745 That water serves as a lubricant betwen the glass bottle 0:02:54.745,0:02:56.563 and the center plug of ketchup, 0:02:56.563,0:02:59.300 and so the ketchup flows. 0:02:59.300,0:03:02.036 Another possibility is that the particles slowly rearrange themselves 0:03:02.036,0:03:05.747 into lots of small groups, which then flow past each other. 0:03:05.747,0:03:08.636 Scientists who study fluid flows are still actively researching 0:03:08.636,0:03:11.533 how ketchup and its merry friends work. 0:03:11.533,0:03:13.581 Ketchup basically gets thinner the harder you push, 0:03:13.581,0:03:16.636 but other substances like oobleck or some natural peanut butters 0:03:16.636,0:03:19.667 actually get thicker the harder you push. 0:03:19.667,0:03:21.868 Others can climb up rotating rods, 0:03:21.868,0:03:24.235 or continue to pour themselves out of a beeker, 0:03:24.235,0:03:26.164 once you get them started. 0:03:26.164,0:03:27.602 From a physics perspective, though, 0:03:27.602,0:03:30.425 ketchup is one of the more complicated mixtures out there. 0:03:30.425,0:03:32.468 And as if that weren't enough, the balance of ingredients 0:03:32.468,0:03:35.567 and the presence of natural thickeners like xanthan gum, 0:03:35.567,0:03:38.162 which is also found in many fruit drinks and milkshakes, 0:03:38.162,0:03:39.405 can mean that two different ketchups 0:03:39.405,0:03:41.796 can behave completely differently. 0:03:41.796,0:03:43.960 But most will show two telltale properties: 0:03:43.960,0:03:46.480 sudden thinning at a threshold force, 0:03:46.480,0:03:48.498 and more gradual thinning after a small force 0:03:48.498,0:03:50.667 is applied for a long time. 0:03:50.667,0:03:53.377 And that means you could get ketchup out of the bottle in two ways. 0:03:53.377,0:03:56.315 Either give it a series of long, slow languid shakes 0:03:56.315,0:03:58.668 making sure you don't ever stop applying force, 0:03:58.668,0:04:01.936 or you could hit the bottle once very, very hard. 0:04:01.936,0:04:04.636 What the real pros do is keep the lid on, 0:04:04.636,0:04:07.035 give the bottle a few short, sharp shakes 0:04:07.035,0:04:08.894 to wake up all those tomato particles, 0:04:08.894,0:04:10.542 and then take the lid off 0:04:10.542,0:04:20.543 and do a nice controlled pour onto their heavenly fries. 0:04:20.543,9:59:59.000