Can you read in the car? If so, consider yourself pretty lucky. For one-third of the population, looking at a book while moving along in a car or a boat or train or plane quickly makes them sick to their stomach. But why do we get motion sickness in the first place? Well, believe it or not, scientists aren't exactly sure. The most common theory has to do with mismatched sensory signals. When you travel in a car, your body gets two different messages. Your eyes are seeing the inside of a vehicle, which doesn't seem to be moving. Meanwhile, your ear is telling your brain you're accelerating. Wait, your ear? Your ear has another important function besides hearing. In its innermost part lies a group of structures known as the vestibular system, which gives us our sense of balance and movement. Inside there are three semicircular tubules that can sense rotation, one for each dimension of space. And there are also two hair-lined sacks filled with fluid. When you move, the fluid shifts and tickles the hairs, telling your brain if you're moving horizontally or vertically. All this tells your body which direction you're moving in, how much you've accelerated, even at what angle. In a car, your vestibular system correctly senses your movement, but your eyes don't see it, especially when glued to a book. The opposite can happen. You're at the movies, and the camera makes a sweeping move. This time, your eyes think you're moving while your ear knows you're sitting still. But why does this conflicting information make us feel so terrible? Scientists aren't sure, but they think there's an evolutionary explanation. Fast moving vehicles and video recordings have only existed in the last couple of centuries, a blink in evolutionary time. For most of our history, there wasn't that much that could cause this sensory mix-up, except for poisons. And because poisons are not the best thing for survival, our bodies evolved a direct but unpleasant way to get rid of what we ate that was causing the confusion. It's a pretty reasonable theory, but it leaves things unexplained, like why women are more affected by motion sickness than men, or why passengers get more nauseous than drivers. Another theory suggests that the cause is more about the way some unfamiliar situations make it harder to maintain our natural body posture. Studies show that being immersed in water or just changing your stance can greatly reduce the effects of motion sickness. But we don't really know what's going on. We know the more common remedies for car queasiness -- looking at the horizon, over-the-counter pills, chewing gum, but none are totally reliable nor can they handle intense motion sickness and sometimes the stakes are far higher than just not being bored during a long car ride. At NASA, where astronauts are hurled into space at 17,000 miles per hour, motion sickness is a serious problem. In addition to researching the latest space-age technologies, NASA also spends a lot of time figuring out how to keep astronauts from vomiting up their space rations. Like understanding the mysteries of sleep or curing the common cold, motion sickness is one of those seemingly simple problems that, despite amazing scientific progress, we still know very little about. Perhaps one day the exact cause of motion sickness will be found, and with it, a completely effective way to prevent it, but that day is still on the horizon.
你能夠在車上看書嗎? 如果可以,那麼先恭喜你非常幸運 約有三分之一的人口 在移動中的車 船 火車 飛機 上看書會感到不適 但為什麼會感到這種「移動中的不適」 信不信由你 科學家們也沒有很確定 而最常見的理論是 身體感應訊號的錯置 當你坐在移動中的車子上時 你的身體同時接收兩種不同的訊號 你的眼睛看著車自內部 沒有移動的部份 同時,你的耳朵告訴你的大腦 你現在處在加速的狀態 等等!你的耳朵? 沒錯,就是你的耳朵 有著除了聽覺外很重要的功能 在耳朵最裡面有一組架構 稱作「內耳前庭系統」 這個系統負責人體平衡與移動的感知 內耳前庭內部有三個半圓的細管 可以感知轉動 每一個細管負責一個維度 此外還有兩個毛髮排列的囊袋 裡面充滿液體 所以當你移動時 液體跟著移動並觸碰到毛髮 這時你的大腦會收到通知 不管你是水平移動 還是垂直移動 這些元素的加總 讓你的身體可以感知 你正在往哪個方向移動 你移動時的加速度是多少 甚至往哪個角度移動 所以當你在車裡面時 你的內耳前庭系統 正確的感知你的移動方向 但是你的眼睛並不會看見移動方向 尤其當你的眼正專注在書本上時 兩者感知相反也是可能發生的 例如當你坐在電影院裡 而投影機投射一個大面積移動 這次換成你的眼睛 認為你正處在移動中 而你的耳朵感知到你其實是坐著不動 只是究竟為何這樣的資訊衝突 會讓我們感到如此不適呢? 科學家對於這個問題 仍然沒有一個確定的答案 不過他們還是有一個 基於演化的解釋 你知道,快速前進的車輛與錄影帶播映 是最近幾世紀才出現的 存在時間並不長 人類演化歷史中 並沒有這麼多 可以造成感知混河錯亂的事物 除了毒藥外 而因為毒藥 對於生存不利 我們的身體演化出直接 但不這麼讓人舒適的方式 來使我們擺脫那些我們可能吃下 而造成混淆衝突的東西 這個理論看似十分合理 但仍然留下許多未能解釋的部分 例如:為何女人 比起男人更容易有移動中的不適感 或是為何乘客比起司機 更容易感到噁心不適 另一個理論解釋說 會造成此種不適的原因 與不熟悉環境比較相關 因其讓我們的身體 更難維持自然的姿勢 研究指出 浸泡在水裡 或單純的改變姿勢 可以大幅降低這種 移動中產生的不適感 但同樣地,我們並不了解其真正的原因 我們知道其他常見的補救措施 當在車上感到不適的時候 可以往地平線看 嚼口香糖 服用成藥 但是這些方法並不是完全可靠 也無法完全處理 強烈的不適感 而有時這種狀態 強烈度遠超乎一般 在長途車程中 在美國太空總署,太空人進入 一個以每秒17000英哩移動的空間 移動中產生的不適感變得極度強烈 所以除了研究 最新的太空科技 美國太空總署也花了許多時間 試圖來想出 如何讓太空人不會因此嘔吐的辦法 他們仔細準備空間配置量 和了解睡眠的祕辛 或解決感冒問題一般 移動中造成的不適感仍是屬於 那些看似簡單 但若無重大科學進展 我們仍然不會知道的問題 也許有一天 切確的答案會被找出 而了解原因後 即可找出有效避免這種不適的方法 不過那ㄧ天的到來目前仍看似遙遙無期