While it's not impossible for birds to fly in the rain, they usually choose not to. You may see birds fly for a few seconds in poor weather, but most of them prefer to stay put on rainy days.

Why does rain make it harder for birds to fly? You might imagine that moving through the air while being pelted by raindrops would be pretty unpleasant. However, it's not the rain itself that makes flying difficult. Instead, birds are influenced by the drop in the air pressure that comes with most rainstorms. When pressure drops, the air is less thick, which makes it harder for birds to fly. Moving through the sky in areas of low air pressure takes a lot of energy.

Most birds need to eat several times a day—rain or no rain. Luckily, most birds' feathers（羽毛）are highly waterproof（防水的）, protecting the skin beneath. Many birds can also make oil that they can spread over their feathers to further protect themselves from the rain. Most birds don't like rain. In fact, in a 2010 study, a team of researchers studied birds living in a Costa Rican rainforest. They found that the birds had higher levels of stress hormone（应激激素）on rainy days. That may not surprise you. After all, many animals feel stressed out during storms. Pet owners often find that rain and thunder make their animals nervous. Some animals are so strongly influenced by nature that they almost seem to forecast the future.

No one really knows how many birds die during a storm or series of storms. But the number is certainly higher than usual. They fly into trees or windows; they get lost over the ocean or a large lake; their food sources are made more difficult to get but, at the same time, they need more food to get warm. However, if rain continues for some time, birds will have to challenge the storm.

In a digital age, we almost never write things by hand. However, multiple studies have shown that this act has many benefits.

New brain research, led by researchers at the Norwegian University of Science and Technology, confirms the same choosing handwriting over using a keyboard results in better learning and memory.

“When you write your shopping list or lecture notes by hand, you simply remember the content better afterwards,” said Audrey Van der Meer, author of the study.

The study was conducted using equipment to track and record brain wave activity. The participants included 12 young adults and 12 children. This is the first time that children have participated in such a study. Each subject was asked to write by hand and type on a keyboard while wearing a hood(风帽) with over 250 electrodes(电极). The sensors(传感器)in the electrodes are very sensitive and pick up the electrical activity that takes place in the brain. Each examination took 45 minutes per person.

The results showed that the brain in both young adults and children is much more active when writing by hand than when typing on a keyboard. According to Van der Meer, plenty of senses are activated (激活) by pressing a pen on paper, seeing the letters written and hearing the sound made while writing. These sense experiences build contact between different parts of the brain, opening the brain up for learning.

Van der Meer believes that the outcomes stress the importance of children being challenged to draw and write at an early age, especially at school. “Learning to write by hand is a bit slower process, but it’s important for children to go through the tiring phase of learning to write by hand”, she said.

The hand movements used to form the shapes of letters are beneficial in several ways. “If you use a keyboard, you use the same movement for each letter. Writing by hand requires control of your fine motor(精细动作)skills and senses. It’s important to put the brain in a learning state as often as possible,” Van der Meer added. For example, you might use a keyboard to write an essay, but you should take notes by hand during a lecture.

Some ultra-processed foods increase the risk of developing cancer, heart disease and diabetes, but others are good for you, new research suggests. A major new international study has found that regular consumption of meat products, such as sausages and sugary drinks make it more likely that someone will get those diseases. But bread and cereals actually reduce someone’s risk of them, because they contain fibre despite also being ultra-processed foods (UPF), the same researchers also concluded in findings published in The Lancet.

Similarly, sauces, spreads and condiments are also bad for human health, but not as much as animal products and soft drinks. However, several other major types of UPF previously seen as harmful: sweets and desserts, ready meals, savoury snacks and plant-based alternatives to meat products also got the all-clear. They are “not associated with risk of multi-morbidity (多重病症)”, said the authors.

Experts said the findings showed that regarding all UPF products as bad for health is unwise and unwarranted. Like several other recent research projects, the new study did conclude that UPF harms human health and makes it more likely that someone who consumes a lot of it would suffer a potentially fatal event, such as a heart attack or stroke. However, it also gives a more detailed picture of exactly which UPF products do and do not heighten that risk.

The authors said, “We found that higher consumption of UPF was associated with a higher risk of multi-morbidity of cancer and cardio-metabolic diseases.” People keen to lower their risk should replace some but not all UPF in their diet with “similar but less processed foods for the prevention of cancer and cardio-metabolic multi-morbidity” or follow the Mediterranean diet. Multi-morbidity is when someone has at least two life-shortening diseases at the same time, such as cancer and heart disease.

Heinz Freisling, a co-author of the paper and expert at the World Health Organization said, “Our study emphasises that it is not necessary to completely avoid ultra-processed foods; rather, their consumption should be limited, and preference be given to fresh or minimally processed foods.”