WEBVTT 00:00:06.891 --> 00:00:08.119 Can you read in the car? 00:00:08.143 --> 00:00:09.969 If so, consider yourself pretty lucky. 00:00:09.993 --> 00:00:11.589 For one-third of the population, 00:00:11.613 --> 00:00:13.720 looking at a book while moving along in a car 00:00:13.744 --> 00:00:15.043 or a boat or train or plane 00:00:15.067 --> 00:00:17.026 quickly makes them sick to their stomach. 00:00:17.050 --> 00:00:19.574 But why do we get motion sickness in the first place? 00:00:19.598 --> 00:00:22.272 Well, believe it or not, scientists aren't exactly sure. 00:00:22.296 --> 00:00:23.842 The most common theory has to do 00:00:23.866 --> 00:00:25.447 with mismatched sensory signals. 00:00:25.471 --> 00:00:28.571 When you travel in a car, your body gets two different messages. 00:00:28.595 --> 00:00:30.692 Your eyes are seeing the inside of a vehicle, 00:00:30.716 --> 00:00:32.241 which doesn't seem to be moving. 00:00:32.265 --> 00:00:35.272 Meanwhile, your ear is telling your brain you're accelerating. 00:00:35.296 --> 00:00:36.435 Wait, your ear? 00:00:36.459 --> 00:00:39.571 Your ear has another important function besides hearing. 00:00:39.595 --> 00:00:43.402 In its innermost part lies a group of structures known as the vestibular system, 00:00:43.426 --> 00:00:45.713 which gives us our sense of balance and movement. 00:00:45.737 --> 00:00:47.797 Inside there are three semicircular tubules 00:00:47.821 --> 00:00:50.543 that can sense rotation, one for each dimension of space. 00:00:50.667 --> 00:00:53.412 And there are also two hair-lined sacks filled with fluid. 00:00:53.436 --> 00:00:55.976 When you move, the fluid shifts and tickles the hairs, 00:00:56.000 --> 00:00:58.960 telling your brain if you're moving horizontally or vertically. 00:00:58.984 --> 00:01:01.780 All this tells your body which direction you're moving in, 00:01:01.804 --> 00:01:04.069 how much you've accelerated, even at what angle. 00:01:04.093 --> 00:01:05.150 In a car, 00:01:05.175 --> 00:01:07.721 your vestibular system correctly senses your movement, 00:01:07.745 --> 00:01:10.611 but your eyes don't see it, especially when glued to a book. 00:01:10.635 --> 00:01:11.782 The opposite can happen. 00:01:11.806 --> 00:01:14.849 You're at the movies, and the camera makes a sweeping move. 00:01:14.873 --> 00:01:16.860 This time, your eyes think you're moving 00:01:16.884 --> 00:01:18.944 while your ear knows you're sitting still. 00:01:18.968 --> 00:01:22.189 But why does this conflicting information make us feel so terrible? 00:01:22.213 --> 00:01:23.382 Scientists aren't sure, 00:01:23.406 --> 00:01:25.809 but they think there's an evolutionary explanation. 00:01:25.833 --> 00:01:27.849 Fast moving vehicles and video recordings 00:01:27.873 --> 00:01:30.264 have only existed in the last couple of centuries, 00:01:30.288 --> 00:01:31.706 a blink in evolutionary time. 00:01:31.730 --> 00:01:33.966 For most of our history, there wasn't that much 00:01:33.990 --> 00:01:35.784 that could cause this sensory mix-up, 00:01:35.808 --> 00:01:36.879 except for poisons. 00:01:36.903 --> 00:01:40.113 And because poisons are not the best thing for survival, 00:01:40.137 --> 00:01:43.145 our bodies evolved a direct but unpleasant way 00:01:43.169 --> 00:01:45.869 to get rid of what we ate that was causing the confusion. 00:01:45.893 --> 00:01:49.016 It's a pretty reasonable theory, but it leaves things unexplained, 00:01:49.040 --> 00:01:51.912 like why women are more affected by motion sickness than men, 00:01:51.936 --> 00:01:54.234 or why passengers get more nauseous than drivers. 00:01:54.258 --> 00:01:56.751 Another theory suggests that the cause is more about 00:01:56.775 --> 00:01:58.434 the way some unfamiliar situations 00:01:58.458 --> 00:02:00.952 make it harder to maintain our natural body posture. 00:02:00.976 --> 00:02:04.282 Studies show that being immersed in water or just changing your stance 00:02:04.306 --> 00:02:06.677 can greatly reduce the effects of motion sickness. 00:02:06.701 --> 00:02:08.749 But we don't really know what's going on. 00:02:08.773 --> 00:02:11.482 We know the more common remedies for car queasiness -- 00:02:11.506 --> 00:02:14.341 looking at the horizon, over-the-counter pills, chewing gum, 00:02:14.365 --> 00:02:15.832 but none are totally reliable 00:02:15.856 --> 00:02:17.902 nor can they handle intense motion sickness 00:02:17.926 --> 00:02:20.978 and sometimes the stakes are far higher than just not being bored 00:02:21.002 --> 00:02:22.102 during a long car ride. 00:02:22.126 --> 00:02:25.666 At NASA, where astronauts are hurled into space at 17,000 miles per hour, 00:02:25.690 --> 00:02:27.588 motion sickness is a serious problem. 00:02:27.612 --> 00:02:30.595 In addition to researching the latest space-age technologies, 00:02:30.619 --> 00:02:32.060 NASA also spends a lot of time 00:02:32.084 --> 00:02:36.353 figuring out how to keep astronauts from vomiting up their space rations. 00:02:36.377 --> 00:02:39.582 Like understanding the mysteries of sleep or curing the common cold, 00:02:39.606 --> 00:02:42.634 motion sickness is one of those seemingly simple problems that, 00:02:42.658 --> 00:02:46.253 despite amazing scientific progress, we still know very little about. 00:02:46.277 --> 00:02:49.331 Perhaps one day the exact cause of motion sickness will be found, 00:02:49.355 --> 00:02:51.891 and with it, a completely effective way to prevent it, 00:02:51.915 --> 00:02:54.017 but that day is still on the horizon.