1 00:00:05,684 --> 00:00:08,684 French fries are delicious. 2 00:00:08,684 --> 00:00:12,684 French fries with ketchup are a little slice of heaven. 3 00:00:12,684 --> 00:00:14,432 The problem is it's basically impossible 4 00:00:14,432 --> 00:00:16,463 to pour the exactly right amount. 5 00:00:16,463 --> 00:00:19,768 We're so used to pouring ketchup that we don't realize 6 00:00:19,768 --> 00:00:21,851 how weird its behavior is. 7 00:00:21,851 --> 00:00:26,430 Imagine a ketchup bottle filled with a straight up solid like steel. 8 00:00:26,430 --> 00:00:29,475 No amount of shaking would ever get the steel out. 9 00:00:29,475 --> 00:00:32,395 Now imagine that same bottle full of a liquid like water. 10 00:00:32,395 --> 00:00:34,434 That would pour like a dream. 11 00:00:34,434 --> 00:00:36,851 Ketchup, though, can't seem to make up its mind. 12 00:00:36,851 --> 00:00:38,933 Is it is a solid? Or a liquid? 13 00:00:38,933 --> 00:00:41,654 The answer is, it depends. 14 00:00:41,654 --> 00:00:44,846 The world's most common fluids like water, oils and alcohols 15 00:00:44,846 --> 00:00:47,597 respond to force linearly. 16 00:00:47,597 --> 00:00:51,238 If you push on them twice as hard, they move twice as fast. 17 00:00:51,238 --> 00:00:54,355 Sir Isaac Newton, of apple fame, first proposed this relationship, 18 00:00:54,355 --> 00:00:57,739 and so those fluids are called Newtonian fluids. 19 00:00:57,739 --> 00:01:00,695 Ketchup, though, is part of a merry band of linear rule breakers 20 00:01:00,695 --> 00:01:03,286 called Non-Newtonian fluids. 21 00:01:03,286 --> 00:01:06,368 Mayonnaise, toothpaste, blood, paint, peanut butter 22 00:01:06,368 --> 00:01:09,870 and lots of other fluids respond to force non-linearly. 23 00:01:09,870 --> 00:01:11,915 That is, their apparent thickness changes 24 00:01:11,915 --> 00:01:15,336 depending on how hard you push, or how long, or how fast. 25 00:01:15,336 --> 00:01:18,551 And ketchup is actually Non-Newtonian in two different ways. 26 00:01:18,551 --> 00:01:22,849 Way number one: the harder you push, the thinner ketchup seems to get. 27 00:01:22,849 --> 00:01:24,715 Below a certain pushing force, 28 00:01:24,715 --> 00:01:26,717 ketchup basically behaves like a solid. 29 00:01:26,717 --> 00:01:29,134 But once you pass that breaking point, 30 00:01:29,134 --> 00:01:33,384 it switches gears and becomes a thousand times thinner than it was before. 31 00:01:33,384 --> 00:01:35,384 Sound familiar right? 32 00:01:35,384 --> 00:01:39,276 Way number two: if you push with a force below the threshold force 33 00:01:39,276 --> 00:01:41,569 eventually, the ketchup will start to flow. 34 00:01:41,569 --> 00:01:45,158 In this case, time, not force, is the key to releasing ketchup 35 00:01:45,158 --> 00:01:46,992 from its glassy prison. 36 00:01:46,992 --> 00:01:49,620 Alright, so, why does ketchup act all weird? 37 00:01:49,620 --> 00:01:52,634 Well, it's made from tomatoes, pulverized, smashed, thrashed, 38 00:01:52,634 --> 00:01:55,457 utterly destroyed tomatoes. 39 00:01:55,457 --> 00:01:56,801 See these tiny particles? 40 00:01:56,801 --> 00:01:58,586 This is what remains of tomatoes cells 41 00:01:58,586 --> 00:02:01,215 after they go through the ketchup treatment. 42 00:02:01,215 --> 00:02:02,925 And the liquid around those particles? 43 00:02:02,925 --> 00:02:05,967 That's mostly water and some vinegar, sugar, and spices. 44 00:02:05,967 --> 00:02:08,190 When ketchup is just sitting around, 45 00:02:08,190 --> 00:02:11,551 the tomato particles are evenly and randomly distributed. 46 00:02:11,551 --> 00:02:13,967 Now, let's say you apply a weak force very quickly. 47 00:02:13,967 --> 00:02:15,522 The particles bump into each other, 48 00:02:15,522 --> 00:02:17,218 but can't get out of each other's way, 49 00:02:17,218 --> 00:02:18,717 so the ketchup doesn't flow. 50 00:02:18,717 --> 00:02:21,777 Now, let's say you apply a strong force very quickly. 51 00:02:21,777 --> 00:02:24,613 That extra force is enough to squish the tomato particles, 52 00:02:24,613 --> 00:02:25,945 so maybe instead of little spheres, 53 00:02:25,945 --> 00:02:28,827 they get smushed into little ellipses, and boom! 54 00:02:28,827 --> 00:02:30,784 Now you have enough space for one group of particles 55 00:02:30,784 --> 00:02:33,633 to get passed others and the ketchup flows. 56 00:02:33,633 --> 00:02:37,716 Now let's say you apply a very weak force but for a very long time. 57 00:02:37,716 --> 00:02:41,253 Turns out, we're not exactly sure what happens in this scenario. 58 00:02:41,253 --> 00:02:45,009 One possibility is that the tomato particles near the walls of the container 59 00:02:45,009 --> 00:02:47,299 slowly get bumped towards the middle, 60 00:02:47,299 --> 00:02:48,800 leaving the soup they were dissolved in, 61 00:02:48,800 --> 00:02:50,383 which remember is basically water, 62 00:02:50,383 --> 00:02:51,884 near the edges. 63 00:02:51,884 --> 00:02:54,383 That water serves as a lubricant betwen the glass bottle 64 00:02:54,383 --> 00:02:56,436 and the center plug of ketchup, 65 00:02:56,436 --> 00:02:58,551 and so the ketchup flows. 66 00:02:58,551 --> 00:03:01,941 Another possibility is that the particles slowly rearrange themselves 67 00:03:01,941 --> 00:03:05,801 into lots of small groups, which then flow past each other. 68 00:03:05,801 --> 00:03:08,133 Scientists who study fluid flows are still actively researching 69 00:03:08,133 --> 00:03:11,326 how ketchup and its merry friends work. 70 00:03:11,326 --> 00:03:13,411 Ketchup basically gets thinner the harder you push, 71 00:03:13,411 --> 00:03:16,498 but other substances, like oobleck or some natural peanut butters, 72 00:03:16,498 --> 00:03:19,301 actually get thicker the harder you push. 73 00:03:19,301 --> 00:03:21,717 Others can climb up rotating rods, 74 00:03:21,717 --> 00:03:24,090 or continue to pour themselves out of a beeker, 75 00:03:24,090 --> 00:03:26,012 once you get them started. 76 00:03:26,012 --> 00:03:27,384 From a physics perspective, though, 77 00:03:27,384 --> 00:03:30,217 ketchup is one of the more complicated mixtures out there. 78 00:03:30,217 --> 00:03:32,467 And as if that weren't enough, the balance of ingredients 79 00:03:32,467 --> 00:03:35,300 and the presence of natural thickeners like xanthan gum, 80 00:03:35,300 --> 00:03:37,934 which is also found in many fruit drinks and milkshakes, 81 00:03:37,934 --> 00:03:39,605 can mean that two different ketchups 82 00:03:39,605 --> 00:03:41,549 can behave completely differently. 83 00:03:41,549 --> 00:03:44,234 But most will show two telltale properties: 84 00:03:44,234 --> 00:03:46,069 sudden thinning at a threshold force, 85 00:03:46,069 --> 00:03:48,321 and more gradual thinning after a small force 86 00:03:48,321 --> 00:03:50,365 is applied for a long time. 87 00:03:50,365 --> 00:03:53,327 And that means you could get ketchup out of the bottle in two ways: 88 00:03:53,327 --> 00:03:55,966 either give it a series of long, slow languid shakes 89 00:03:55,966 --> 00:03:58,467 making sure you don't ever stop applying force, 90 00:03:58,467 --> 00:04:02,504 or you could hit the bottle once very, very hard. 91 00:04:02,504 --> 00:04:04,717 What the real pros do is keep the lid on, 92 00:04:04,717 --> 00:04:07,132 give the bottle a few short, sharp shakes 93 00:04:07,132 --> 00:04:08,550 to wake up all those tomato particles, 94 00:04:08,550 --> 00:04:10,428 and then take the lid off 95 00:04:10,428 --> 00:04:13,801 and do a nice controlled pour onto their heavenly fries.