Below is a selection from a popular science book.
以下选自一本科普书籍。
If blood is red ,why are verns blue?
血液是红色的，静脉为什么是蓝色？
Actually, veins are not blue at all. They are more of a clear, yellowish color. Although blood looks red when it’s outside the body, when it’s sitting in a vein near the surface of the skin, it’s more of a dark reddish purple color. At the right depth, these blood-filled veins reflect less red light than the surrounding skin, making them look blue by comparison.
事实上，静脉并不是蓝色，它们更像是一种清澈的黄色。虽然血液在体外看起来是红色，但当它位于皮肤表面附近的静脉中时，更像是暗红紫色。在适当的深度，这些充满血液的静脉比周围的皮肤反射更少的红光，对比之下，看起来呈蓝色。
Which works harder, your heart or your brain?
你的心脏和大脑哪个更忙碌？
That kind of depends on whether you’re busy thinking or busy exercising. Your heart works up to three times harder during exercise, and shifts enough blood over a lifetime to fill a supertanker.
这取决于你是忙于思考还是忙于锻炼。运动时心脏的工作强度会提高三倍，一生中转移的血液足以装满一辆超级油罐车。
But, in the long run, your brain probably tips it, because even when you ‘re sitting still your brain is using twice as much energy as your heart, and it takes four to five times as much blood to feed it .
但是，从长远来看，大脑可能会超过它，因为即使你坐着不动，大脑消耗的能量也是心脏的两倍，而且需要四到五倍的血液来提供营养。
Why do teeth fall out, and why don’t they grow back in grown-ups?
牙齿为什么会脱落，成年人的牙齿为什么不会再生？
Baby (or “milk ”) teeth do not last long; they fall out to make room for bigger, stronger adult teeth later on. Adult teeth fall out when they become damaged, decayed and infected by bacteria. Once this second set of teeth has grown in, you’re done. When they’re gone, they’re gone. This is because nature figures you’re set for life, and what controls regrowth of your teeth switches off.
乳牙持有时间不会很长；它们脱落是为了以后为更大、更强壮的恒牙腾出空间。当恒牙受损、腐蚀，被细菌感染时，它们就会脱落。一旦第二副牙齿已经长出，你就完了。当它们脱落了，就真的结束了。这是因为大自然定义了你的一辈子，控制你牙齿再生的开关被关闭了。
Do old people shrink as they age?
老年人会随着年龄的增长而萎缩吗？
Yes and no. Many people do get shorter as they age. But, when they do, it isn’t because they’re shrinking all over. They simply lose height as their spine becomes shorter and more curved due to disuse and the effects of gravity. Many (but not all) men and women do lose height as they get older. Men lose an average of 3-4 cm in height as they age, while women may lose 5cm or more. If you live to be 200 years old, would you keep shrinking till you were, like 60 cm tall, like a little boy again? No, because old people don’t really shrink! It is not that they are growing backwards -- their legs, arms and backbones getting shorter. When they do get shorter, it’s because the spine has shortened a little. Or, more often, become more bent and curved.
是，也不是。许多人确实随着年龄的增长而变矮。但是，当他们这样变矮的时候，并不是因为他们全身都在萎缩。由于废弃和重力的影响，脊椎变得更短、更弯曲，从而失去了高度。随着年龄的增长，许多（但不是所有）男性和女性的身高确实会下降。男性的身高平均会下降3-4厘米，而女性的身高可能会下降5厘米或更多。如果你活到200岁，你会一直缩小到60厘米高，又像个小男孩吗？不会，因为老年人不是真的萎缩！他们不是在逆向生长——他们的腿，手臂和脊椎越来越短。他们变矮是因为脊椎缩短了一点，或者更可能是因为变得更加弯曲。
Why does spinning make you dizzy？
旋转为什么会让人眩晕？
Because your brain gets confused between what you’re seeing and what you’re feeling. The brain senses that you’re spinning using special gravity-and motion-sensing organs in your inner ear, which work together with your eyes to keep your vision and balance stable. But, when you suddenly stop spinning the system goes out of control, and your brain thinks you’re moving while you’re not!
因为你的大脑会混淆你所看到的和你所感受到的。大脑通过内耳中特殊的重力和运动感知器官来感知你在旋转，这些器官与你的眼睛协同工作，保持你的视力和平衡稳定。但是，当你突然停止旋转时，系统就会失控，你的大脑认为你在移动，而你没有！
Where do feelings and emotions come from?
感情和情绪是来自哪里？
Mostly from an ancient part of the brain called the limbic system. All mammals have this brain area --from mice to dogs, cats, and humans. So all mammals feel basic emotions like fear, pain and pleasure. But since human feelings also involve other, newer bits of the brain, we feel more complex emotions than any other animal on the planet.
主要来自大脑中一个称为边缘系统的古老部分。从老鼠到狗、猫和人类，所有哺乳动物都有这个大脑区域。所以所有哺乳动物都能感受到基本的情绪，比如恐惧、痛苦和快乐。但由于人类的感受还涉及大脑的其他更新部分，我们比地球上所有其他动物都能感受到更复杂的情绪。
If exercise wears you out, how can it be good for you?
锻炼使你疲惫，那它对你有什么好处呢？
Because our bodies adapt to everything we do to them. And as far as your body is concerned, it’s “use it, or lose it”! It’s not that exercise makes you healthy; it’s more that a lack of exercise leaves your body weak and easily affected by disease.
因为我们的身体会适应我们对它所做的一切。就你的身体而言，“要么使用，要么失去”！运动并不是让你健康；而是缺乏运动会使你的身体虚弱，容易受到疾病的影响。
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