【推荐1】Below is a selection from a popular science book.

If blood is red, why are veins（静脉）blue?

Actually, veins are not blue at all. They are more of a clear, yellowish colour. 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 colour. At the right depth, these blood-filled veins reflect less and light than the surrounding skin, making them look blue by comparison.

Which works harder, your heart or your brain?

That kind of depends on whether you are 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. 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.

Do old people shrink as they age?

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（脊柱）becomes shorter and more curved due to disuse and the effects of gravity（重力）. 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 5 cm 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 bait and curved.

Why does spinning make you dizzy（眩晕的）?

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!

Where do feelings and emotions come from?

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.

If exercise wears you out, how can it be good for you?

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.

【推荐3】Odors (气味) are complex and often have changeable structures, and can show meaningful information about an animal’s surroundings, like the location of food sources. But it has previously been assumed that mammalian (哺乳动物的) brains can`t fully process these temporal changes in smell because they happen so rapidly, much faster than an animal can smell.

Using behavioral experiments, researchers at the Francis Crick Institute and UCL(University College London)found that mice can, in fact, detect very rapid variations within odors, at rates previously not thought possible. They also showed that mice can use this information to distinguish whether odors are coming from the same or different sources, even if they are very close to each other.

This suggests that the mammalian olfactory (嗅觉的) system is also key in processing the awareness of physical space and surroundings, guiding decisions important to survival.

Andreas Schaefer, group leader of the Sensory Circuits and Neurotechnology Laboratory at UCL says: “From an evolutionary (进化的) point of view our findings make sense as they help to explain why there is a lot of computational power within the olfactory bulb, the part of the brain where the nose sends signals to. It’s not only processing chemicals from odors but also calculating information about physical distance and sources. It would have been strange for evolution to create such processing power in this part of the brain if it were not being used to help the species survive.”

In one key experiment, the scientists trained mice to detect whether two odors were coming from the same source or separate sources. The mice were able to correctly distinguish this difference.

As part of the study, the scientists designed new technologies including a high-speed odor delivery device and equipment that can measure several odors with extremely high precision. These innovations will enable more complicated work on the olfactory bulb, increasing our knowledge of how this brain region processes information about the environment and influences behavior.