1 . NASA will crash a spacecraft into an asteroid (小行星) to try to change its orbit, attempting to prevent humans going the same way as the dinosaurs.

Earth is constantly being disturbed by small pieces of debris (碎片), but they usually burn up or break up long before they hit the ground. Once in a while, however, something large enough to do significant damage makes impact. About 66 million years ago, one such crash is thought to have wiped out the dinosaurs. Someday, something similar could end human beings—unless we can find a way to tackle it.

NASA’s Double Asteroid Redirection Test (Dart) mission is the first attempt to test if such asteroid redirection is a realistic strategy: investigating whether a spacecraft can autonomously reach a target asteroid and intentionally crash into it, as well as measuring the amount of redirection. “If it works, it would be a big deal, because it would prove that we have the technical capability of protecting ourselves,” said Jay Tate, the director of the National Near Earth Object Information Center.

The 610kg Dart spacecraft is scheduled to be launched at the target—the Didymos system—a harmless pair of asteroids consisting of a 163-metre “moonlet” asteroid called Dimorphos that orbits a larger 780-metre asteroid called Didymos (Greek for “twin”). The plan is to crash the spacecraft into Dimorphos when the asteroid system is at its closest to Earth—about 6.8 million miles away.

About 10 days before impact, a miniaturized satellite called LiciaCube will separate from the main spacecraft, enabling images of the impact to be relayed back to Earth. Combined with observations from ground-based telescopes, and an onboard camera that will record the final moments before the crash, these recordings will enable scientists to calculate the degree to which the impact has changed Dimorphos’s orbit. The expectation is that it will change the speed of the smaller asteroid by approximately 1% and reduce its orbit around the larger asteroid.

Then, in November 2024, the European Space Agency’s Hera spacecraft will visit the Didymos system and conduct a further close-up analysis of the consequences of this snooker (斯诺克) game, recording details such as the precise makeup and internal structure of Dimorphos, and the size and shape of the hole left by Dart. Such details are vital for transforming asteroid redirection into a repeatable technique.

Even then, it is impossible that any single redirection strategy would be enough. “The problem is that no two asteroids or comets are alike, and how you redirect one depends on a huge number of variables. There is no silver bullet in this game. What you need is a whole folder of different redirection methods for different types of targets,” said Tate.

So, while this may be one small step towards planetary protection, many more are likely to be necessary to avoid destruction.

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2 . On Wednesday, two things happened. In Syria, 80 people were killed by government airstrikes. Meanwhile, in Florida, Elon Musk’s SpaceX successfully launched and fired a sports car into space. Guess which story has dominated mainstream news sites?

The launch of Musk’s Falcon Heavy rocket, the most powerful ever launched by a private company, went off successfully. Musk sent his cherry-red Tesla roadster running toward Mars, launching “a new space age”. The event attracted phenomenal publicity and made the rocket launch a masterstroke of advertising for Tesla.

Meanwhile, in Syria, where hundreds of thousands of refugees(难民) may be forced to return to unsafe homes, a UN human rights coordinator for Syria said despondently(沮丧地) that he was no longer sure why he bothers to videotape the effects of bombing, since nobody ever pays attention. He wondered what level of violence it would take to make the world care.

There is, perhaps, no better way to appreciate the tragedy of 21st-century global inequality than by watching a billionaire spend $90m launching a $100,000 car into space.

Musk said he wanted to participate in a space race because “races are exciting” and that while strapping his car to a rocket may be “silly and fun … silly and fun things are important”. Thus, anyone who mentions the huge waste the project involves, or the various social uses to which these resources could be put, can be dismissed as a killjoy.

But one doesn’t have to hate fun to question the justification for pursuing a costly new space race at exactly this moment. If we examine the situation honestly, it becomes hard to defend a project like this.

A mission to Mars does indeed sound exciting, but it’s important to have our priorities straight. First, perhaps we could make it so that a child no longer dies of malaria every two minutes. Or we could try to address the level of poverty in Alabama which has become so extreme that the UN investigator did not believe it could occur in a first-world country. Perhaps when violence, poverty and disease are solved, then we can head for the stars.

Many might think that what Elon Musk chooses to do with his billions is Elon Musk’s business alone. If he wanted to spend all his money on medicine for children, that would be nice, but if he’d like to spend it making big explosions and sending his convertible on a million-mile space voyage, that’s his right.

But Musk is only rich enough to afford these money-consuming projects because we have allowed social inequalities to arise in the first place. If wealth were actually distributed fairly in this country, nobody would be in a position to fund his own private space program.

Elon Musk is right: silly and fun things are important. But some of them are an indefensible waste of resources. While there are still humanitarian crises such as that in Syria, nobody can justify vast spending on rocketry experiments.

4 . Earth is lighted up by bioluminescence(生物发光)but，for many of us，seeing the natural phenomenon is a rare treat：Catching the glow(光)of a firefly or witnessing a dolphin swimming through electric blue waters is a thrill.

Researchers are currently engineering glowing flowers and decorative plants that can cast a green light onto our living rooms. Observing plant’s health via its glow can be a way to instantly measure its health,and the side effect is anybody who wants a healthy glowing plant in their living room can have one.

A study published on Monday in Nature Biotechnology shows that this goal is well on its way to being a reality. The study authors announce they’ve created a method that causes plants to glow much brighter,and for a longer period of time,than previous efforts.Plants adapted by this method should be available for purchase within a few years.

The research was conducted through a teamwork between three scientific institutions and Plant,a biotech startup in Moscow.When this team examined a poisonous mushroom,they discovered that caffeic acid is responsible for its bioluminescence. In this new study, the team employed that information and inserted(嵌入)enzymes(酶) —which are specific to the mushroom —into the DNA of tobacco plants.In turn,the enzymes were able to interact with the caffeic acid in the tobacco plants,and cause them to glow both in the dark and in the daylight.

This method,the scientists claimed,made the plants 10 times brighter than previous efforts and the continuous light production didn’t harm the health of the plants. Interestingly, the light decreased as the leaves aged—but it also increased when the leaves were damaged. In turn, the team suggested this method could also help other researchers monitor plant responses to various pressures and changes in the environment. If a plant is short of water or a hungry sheep is harming a plant,bioluminescence could warn of this damage before it’s too late.

5 . It’s a struggle to learn a second language at any age. Now, in a new study, scientist have found out the exact age after which your chances of reaching fluency in a second language seem to plummet: 10.

The study published in the journal Cognition, found that it’s “nearly impossible” for language learners to reach native-level fluency if they start learning a second language after age 10. “It turns out you’re still learning fast,” says study co-author Joshua Hartshorne. “It’s just that you run out of time, because your ability to learn starts dropping at around 17 or 18 years old,” People who start a few years after age 10 may still become quite good at a language, the authors say, but they are unlikely to become fluent.

Kids may be better than adults at learning new languages for sound reasons. Children’s brains are more plastic than those of adults, meaning they’re better able to adapt and respond to new information. Kids may also be more willing to try new things than adults are. Their comparatively new understanding of their native language may also be advantageous.

These findings may seem discouraging, but it was inspiring for scientists to learn that the key period for fluent language learning might be longer than previously thought. Some scientists believed that the window begins to close shortly after birth, while others made it longer to very early childhood. Compared with those judgments, age 17 or 18—when language learning ability starts to drop off—seems relatively old.

For this study, the researchers created an online test promising to guess people’s native language and home country based on their responses to English grammar questions. Almost 670,000 people took it, giving the researchers huge amounts of data from English speakers of many ages and backgrounds. Examining the responses and grammar mistakes allowed them to made unusually exact judgments about language learning.

8 . Rescarchers in the US treated healthy mice with a form of gene therapy that refreshed older cells, making the animals more youthful according to biological markers that are used to measure the effects of ageing. Repeating the trick in humans is far from straightforward, but the findings will fuel interest in new therapiesthat aim to slow or reverse theageing process as a means of tackling age-related diseases such as cancers and Alzheimer’s.

The scientists drew on previous work by the Japanese Nobel winner Prof Shinya Yamanaka, who showed that a mixture of four molecules(原子)—known as Yamanaka factors—can turn adult cells into youthful stem cells that are capable of forming almost any tissue (组织) in the body.

Writing in the journal Nature Aging,the US team led by Jasper and Prof Juan Carlos Izpisua Belmonte at the Salk Institute in California and the San Diego Altos Institute, found that mice who received Yamanaka factors for several months were similar to younger animals in many ways, with their skin in particular showing signs of rejuvenation(恢复青春).

The experiments showed that rejuvenation was more effective when the therapy was given for a long time—7 to 10 months—starting when the animals were 12 to 15 months old, equal to age 35 to 50 in humans. Whén older animals, equal to 80 years old in human terms, were treated for one month, the scientists saw little impact.

Rather than using Yamanaka factors to rejuvenate aged humans, many scientists suspect that new drugs will be needed to partially reprogram cells safely and effectively. “In theory, biological age reversal or reduction could be possible. However, we are at very early stages where we need to understand the basic science behind it much better,” said Dr.Tamir Chandra, an expert in the biology of ageing at the University of Edinburgh.