If so, consider yourself pretty lucky.

如果可以，那麼你是很幸運了。

For about 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.

對於約三分之一的人口來說，不論是在車上、船上、火車上還是飛機上看書，都可以讓他們反胃想吐。

But why do we get motion sickness in the first place?

但人類究竟為什麼會有旅行暈眩的狀況呢？

Well, believe it or not, scientists aren't exactly sure.

信不信由你，但連科學家都不太確定。

The most common theory has to do with mismatched sensory signals.

最常見的理論與感知訊號的錯配有關。

When you travel in a car, your body is getting two very different messages.

當你坐在車子裡時，你的身體會接收到兩種非常不同的訊息。

Your eyes are seeing the inside of a vehicle, which doesn't seem to be moving.

你的雙眼看著汽車似乎完全靜止的內部。

Meanwhile, your ear is actually telling your brain you're accelerating.

同時，你的耳朵卻告訴大腦你正在加速移動。

Wait, your ear?

等等，你的耳朵？

Yeah, your ear actually has another important function besides hearing.

沒錯，你的耳朵除了聽力之外，其實還有另一個重要功能。

In its innermost part lies a group of structures known as the vestibular system, which gives us our sense of balance and movement.

在耳朵最深處，有一組稱為「前庭系統」的結構，讓人類得以擁有平衡感和動感。

Inside there are three semicircular tubules that can sense rotation, one for each dimension of space.

其中有三個可以感應旋轉的半規管，內部每個維度空間有一個。

And there are also two hair-lined sacks that are filled with fluid.

還有兩個充滿液體、內壁佈滿細毛的囊袋。

So when you move, the fluid shifts and tickles the hairs, telling your brain whether you are moving horizontally or vertically.

所以當你在移動時，液體會波動並搔弄毛細胞，告訴大腦你是水平或垂直移動。

With all these combined, your body can sense which direction you're moving in, how much you've accelerated, even at what angle.

這些綜合在一起後，你的身體可以感知你的移動方向、加速程度，甚至是移動角度。

So, when you are in the car, your vestibular system correctly senses your movement, but your eyes don't see it, especially if they are glued to a book.

所以當你在車子裡時，你的前庭系統正確地感應到你的動作，但是你的眼睛沒有偵測到，尤其如果你又緊盯著書本。

The opposite can happen, too.

相反狀況也有可能。

Say you are sitting in a movie theater and the camera makes a broad, sweeping move.

假設你坐在電影院裡，鏡頭有了大幅的移動。

This time, it's your eyes that think you're moving while your ear knows that you're sitting still.

這時，是眼睛以為你在移動，但耳朵知道你坐著不動。

But why does this conflicting information have to make us feel so terrible?

但這種相牴觸的資訊，為什麼非得讓我們感到這麼糟糕呢？

Scientists aren't sure about that either, but they think that there's an evolutionary explanation.

科學家對這一點也不太確定，但他們認為有一個演化論上的解釋說法。

You see, both fast moving vehicles and video recordings have only existed in the last couple of centuries, barely a blink in evolutionary time.

是這樣的，快速移動的車輛以及錄影畫面只存在於僅幾個世紀，對於演化時間來說不過是一眨眼的事。

For most of our history, there just wasn't that much that could cause this kind of sensory mix-up.

綜觀人類歷史，多半沒有太多會造成這種感官錯亂的東西。

Except for poisons.

除了毒藥。

And because poisons are not the best thing for survival, our bodies evolved a very direct but not very pleasant way to get rid of whatever we might have eaten that was causing the confusion.

又因為毒藥對生存不是什麼好東西，人體演化出一個直接又不太舒服的方式，排除我們誤食、造成錯亂的任何東西。

This theory seems pretty reasonable, but it leaves a lot of things unexplained, like why women are more affected by motion sickness than men, or why passengers get more nauseous than drivers.

這個理論看似合理，但仍有很多未解之謎，例如女性為何較容易受旅行暈眩影響，或者乘客為什麼比駕駛更容易反胃。

Another theory suggests that the cause may have more to do with the way some unfamiliar situations make it harder to maintain our natural body posture.

另一個理論建議暗示，起因可能與某些陌生情境讓人類較難以維持自然姿勢有關。

Studies have shown that being immersed in water or just changing your stance can greatly reduce the effects of motion sickness.

研究顯示，沉浸在水之中或是改變站姿可以大幅降低旅行暈眩的影響。

But, again, we don't really know what's going on.

不過，我們一樣不太清楚就事發生了什麼事。

We all do know some of the more common remedies for car queasiness—

我們都知道一些克服暈車的常見妙方──

looking at the horizon, chewing gum, taking over-the-counter pills—

眺望水平線、嚼口香糖、吃暈車藥──

but none of these are totally reliable, nor can they handle really intense motion sickness.

但這些都不是完全可靠，也不能解決嚴重的旅行暈眩。

And sometimes, the stakes are far higher than just not being bored during a long car ride.

而有時候，情勢比希望長途搭車不無聊還要重大。

At NASA, where astronauts are hurled into space at 17,000 miles per hour, motion sickness is a serious problem.

在美國太空總署，太空人以每小時 17,000 英里的速度被拋入太空中，旅行暈眩變成很嚴重的問題。

So, in addition to researching the latest space-age technologies, NASA also spends a lot of time trying to figure out how to keep astronauts from vomiting up their carefully prepared space rations.

所以除了研究最新的航太科技，太空總署也花了大把時間研究如何防止太空人吐掉嚴謹配給的食糧。

Much like understanding the mysteries of sleep or curing the common cold,

就像了解睡眠的奧秘或是治癒感冒一樣，

Motion sickness remains one of those seemingly simple problems that, despite amazing scientific progress, we still know very little about.

旅行暈眩仍舊屬於看起來很簡單，但無論科學有多卓越的進步，我們都了解甚少的問題。

Perhaps one day, the exact cause of motion sickness will be found, and with it, a completely effective way to prevent it.

或許有一天，旅行暈眩的確切起因會被發現，完全有效的預防方式也會隨之而來。

But that day is still on the horizon.

但那一天，還沒到來。