【推荐1】Getting a solid night’s rest when you’re sick can seem like an unattainable goal for any number of reasons. It’s difficult to fall asleep and stay asleep when you’re troubled by a stuffy nose, a constant cough, or other unbearable symptoms(症状). Fevers can make quality sleep even harder, thanks in part to fever dreams: especially vivid, unbelievable, or downright disturbing dreams that occur when you have a fever.

As the Sleep Foundation explains, fever dreams sometimes involve spatial distortion, such as moving walls and melting objects; threats or danger, which can be anything from insects to terrorists; and illness. If you were to have a dream fitting this description when you weren’t sick, you might just regard it as a common nightmare(噩梦). But since people seem to experience such strange dreams more often during fevers, it’s given rise to the idea that the two things must be linked.

While there’s a lot about fever dreams we don’t know, there is at least a little evidence supporting the theory that some people’s fever dreams are different from their regular dreams. In one study from 2016, researchers asked 62 people to describe past fever dreams and found them to be more unbelievable, more emotionally intense, and often negatively toned than regular dreams from an age and gender matched sample. Of the 164 people who participated in a 2020 survey, 100 reported fever dreams. The researchers noted that these dreams included more references to health and temperature sensations(感觉)compared to normal most recent dreams.

As for why fevers beget strange nightmares, scientists have some ideas. “One theory is that the brain doesn’t process sensations normally when we have a fever,” Dr Beth Malow, director of Vanderbilt University Medical Center’s sleep division, told Health in 2020. So burning up in your bed might just clearly show itself in a dream full of melting objects and seemingly unrelated dangers.

【推荐3】China welcomed three heroic astronauts home on April 16. The re-entry module (返回舱) carrying Zhai Zhigang, Wang Yaping and Ye Guangfu touched down safely at the designated Dongfeng Landing Site in Inner Mongolia autonomous region. This ended the Shenzhou XIII astronauts’ six-month space mission.

This return marks a major breakthrough for China’s efforts in space. Let’s look at some of the technical details of the mission.

Speed record

The mission set a new speed record. The Shenzhou XII return capsule revolved around the Earth 11 times over 24 hours, before returning on Sept 17, 2021. This time Shenzhou XIII shortened the time to about 9 hours, orbiting the Earth five times.

The Shenzhou XIII mission was simplified to only five orbits and was designed to return more efficiently, according to the Chinese Academy of Space Technology (CAST).

This approach required more precise control of the spacecraft and more accurate orbital calculations. This meant that when the spacecraft separated, it could quickly target the landing area, calculate the return path, and adjust its altitude, Wang Ya’nan, editor-in-chief of Beijing-based Aerospace Knowledge magazine, told the Global Times.

“Having the ability to adopt such a fast return method indicates that China’s return technology for manned missions is very mature and reliable,” Wang added.

Temperature control

Another challenge for astronauts returning to Earth is traveling through the atmosphere. After the re-entry capsule enters the atmosphere, there is fierce friction with the air. The surface temperature of the capsule can reach thousands of degrees.

To solve this problem, the researchers designed a heat-resistant coating on the surface of the Shenzhou XIII return capsule. They also laid a layer of ablative material (烧蚀材料) that sublimated (升华) and fell off when the temperature reached a certain level, taking a lot of heat with it, according to People’s Daily Online.

Landing

Landing upright is the ideal way to land, ensuring astronauts have the softest landing, Pang Zhihao, a spaceflight researcher in Beijing, told Science and Technology Daily.

【推荐2】In the animal kingdom, parents adopt babies that aren’t their own, and even other species. Why do they do it?

For foster(领养) parents, there are huge costs, with no promise of passing on genes.     1    , because it seems to be wholly altruistic(利他主义的). But this makes it especially confusing in animals, who do not have the cultural influences we do.

One of the most striking places to see adoption in the animal kingdom is AnoNuevo Island, rising from the sea less than one kilometer off the rocky California coast.     2    

From 1976, scientist Marianne Riedman studied adoption among the seals and why it was happening. It’s a crowed beach, with high tides and rough surf, which explains why many little seals each year were separated from their mothers at least once, some permanently.

The researchers counted a total of 572 adopted little seals over the course. Interestingly, some adult seals were likely than others to become foster parents. For one thing, all the foster parents were female.     3     Yet among females, the most common foster seal was a mother who had lost her own child. Why might this be? One possible reason is that adoption helped these females reproduce later on.

Regular nursing may cause them to give ovulation(排卵).     4    

Another possibility is that mothers are prepared to care for their children immediately following birth.     5     the motivation towards care may be so great that they redirect their attention onto other unrelated little animals.

【推荐3】How did life come about on Earth? Did it appear in a flash of light? Well, not exactly. A study published in the journal Nature Communications in March shows that lightning may have played a significant role in the creation of life on Earth.

When lightning hits sand, soil or stone, it melts the materials into a glassy material called fulgurite (闪电熔岩). When a group of researchers examined a particular fulgurite, they found a thick, tree-root-like structure extending down about a foot and a half (about 0.46 meters). “(It was) just entirely made of glass and (had), like, burned soil on the outside of it,” said Benjamin Hess, study author and graduate student at Yale University, US.

But what Hess and his colleagues at the University of Leeds, UK, found inside the fulgurite was even more impressive. According to Science News, “By firing X-rays and electrons (电子) at the fulgurite, and observing how those beams (光线) interacted with the material, the researchers were able to detect its composition.”

They discovered that the fulgurite contained schreibersite (磷铁石), a phosphorus (磷) mineral that can be dissolved in water. Phosphorus is essential for the formation of DNA and cell membranes (薄膜), as well as the formation of teeth and bones in humans, according to the website Phys.org.

It has long been thought that meteorites (陨石) were responsible for delivering this element to Earth. However, life began between 3.5 to 4.5 billion years ago when fewer meteorites were impacting Earth, reported CNN.

According to MSN, Hess and his colleagues estimated that early Earth saw one to five billion lightning flashes every year. Of those, anywhere from 100 million to 1 billion would have struck the ground annually, accounting for between 110 to 11,000 kg of phosphorus per year. While this is a large range, “even the low end is enough to potentially fuel the first life forms, and a quantity that may have eventually exceeded meteor strikes”, MSN reported.