My father was always a good gardener. One of my earliest memories is standing without shoes in the freshly tilled soil, my hands blackened from digging in the ground.

    As a child, I loved following Dad around in the garden. I remember Dad pushing the tiller(耕作机) ahead in perfectly straight lines. Dad loved growing all sorts of things: yellow and green onions, watermelons almost as big as me, rows of yellow corn, and our favorite — red tomatoes.

    As I grew into a teenager, I didn't get so excited about gardening with Dad. Instead of magical land of possibility, it had turned into some kind of prison. As Dad grew older, his love for gardening never disappeared. After all the kids were grown and had started families of their own, Dad turned to gardening like never before. Even when he was diagnosed with cancer, he still took care of his garden.

    But then, the cancer, bit by bit, invaded his body. I had to do the things he used to do. What really convinced me that Dad was dying was the state of his garden that year. The rows and rows of multicolored vegetables were gone. Too tired to weed them, he simply let them be. He only planted tomatoes.

    For the first few years after he died, I couldn't even bear to look at anyone's garden without having strong memories pour over me like cold water from a bucket. Three years ago, I decided to plant my own garden and started out with just a few tomatoes. That morning, after breaking up a fair amount of soil, something caught the corner of my eye and I had to smile. It was my eight-year-old son Nathan, happily playing in the freshly tilled soil.

    There are an extremely large number of ants worldwide. Each individual (个体的) ant hardly weigh anything, but put together they weigh roughly the same as all of mankind. They also live nearly everywhere, except on frozen mountain tops and around the poles. For animals their size, ants have been astonishingly successful, largely due to their wonderful social behavior.

    In colonies (群体) that range in size from a few hundred to tens of millions, they organize their lives with a clear division of labor. Even more amazing is how they achieve this level of organization. Where we use sound and sight to communicate, ants depend primarily on pheromone (外激素), chemicals sent out by individuals and smelled or tasted by fellow members of their colony. When an ant finds food, it produces a pheromone that will lead others straight to where the food is. When an individual ant comes under attack or is dying, it sends out an alarm pheromone to warn the colony to prepare for a conflict as a defense unit.

    In fact, when it comes to the art of war, ants have no equal. They are completely fearless and will readily take on a creature much larger than themselves, attacking in large groups and overcoming their target. Such is their devotion to the common good of the colony that not only soldier ants but also worker ants will sacrifice their lives to help defeat an enemy.

    Behaving in this selfless and devoted manner, these little creatures have survived on Earth, for more than 140 million years, far longer than dinosaurs. Because they think as one, they have a collective (集体的) intelligence greater than you would expect from its individual parts.

    The UK government has announced plans to tackle sources of air pollution, including popular wood-burning stoves, but its Clean Air Strategy, which was unveiled last week, fails to address the real problem.

    Although pollution from woodburning stoves is a relatively new problem for the UK, it has long been a major one in countries such as Canada and New Zealand. And the take-home message from them as to controlling the release of harmful particulates in the air is simple: ban wood burning.

    "There does not seem to be a limit below which there is no impact on health," says Gary Fuller at King's College London, whose team has shown that wood burning is now the source of a third of particulate pollution in UK cities.

    As New Scientist reported last year, families with wood burners are likely to be exposed to the highest levels of pollution and their neighbours are next in the firing line, given that the particulates produced can easily escape from homes. Despite this, the UK government isn't planning a ban. Instead, it wants "to prohibit the sale of the most polluting fuels", such as wet wood. What's more, lots of people with wood burners don't buy wood from shops. Instead, they scrounge it from wherever they can, with building waste one popular source. This is a disaster in pollution terms as treated or painted wood can release highly toxic chemicals when burned. The plan is also to "ensure that only the cleanest stoves are available for sale by 2022". But even the cleanest stove produces eight times as much pollution as a diesel truck, says Fuller.

    Some cities actually required old wood stoves to be replaced with cleaner new ones. That has helped, but wood burning remains a major source of pollution, says Fuller. In most cases, conventional gas central heating plus properly insulating (使隔热) your home is less harmful in global-warming terms than switching to a wood burner.

    Finally, there are separate but related EU laws that set limits on the maximum allowable concentrations of specific pollutants in the air at individual locations. The UK frequently breaches these: London's Oxford Street often hits its annual limit within the first weeks of each year. As a result, the UK government has lost a series of court cases brought by the environmental organization ClientEarth. Separately, on 17 May, the UK and five other countries were referred to the Court of Justice of the European Union for their repeated failures to keep to these limits. If the government really wants to clean up the UK's air, it has a lot more work to do.

    If you're a fan of smart technology, you may have had some sleepless nights lately.

    That's because Alexa, the artificial intelligence (AI) behind US company Amazon's Echo smart speakers, has been "letting out an automatic, creepy (令人毛骨悚然的) cackle," for no apparent reason, according to BBC News.

    Many social media users shared their stories of Alexa scaring them with the seemingly unprompted laugh.

    "Every time Alexa laughs, an angel dies," Tesla and SpaceX founder Elon Musk joked on social media.

    On March 7, Amazon released an update that fixed the problem, saying that the laugh was triggered (引发) by Echo devices mistakenly thinking that users had said the command "Alexa, laugh".

    However, what should have been a funny story raised the ongoing topic of man versus machine.

    With the rise of artificial and robotic technology, "Digital machines have started to demonstrate (展示) broad abilities in pattern recognition, complex communication, and other fields that used to only belong to human," wrote Erik Brynjolfsson and Andrew McAfee in their book The Second Machine Age: Work, Progress, and Prosperity in a Time of Brilliant Technologies. They believe that AI will "do more and more, and our lives will get better".

    However, ever since the earliest days of AI, there have been concerns that some day, software will take over the world, leaving the fate of humans unknown.

    "With artificial intelligence we are summoning (召唤) the demon ," Musk told students during a meeting at MIT in 2014. "If I had to guess at what our biggest existential threat is, it's probably that. So we need to be very careful."

    Many scientists have shared the same concern. The late British physicist Stephen Hawking said at a technology conference in Portugal in November that "computers can, in theory, imitate human intelligence, and exceed it… AI could be the worst event in the history of our civilization." If creators are to safely control AI, however, Hawking suggested that they "employ best practice and effective management".

    "I am an optimist and I believe that we can create AI for the good of the world," he said at the conference. "We simply need to be aware of the dangers, identify them, employ the best possible practice and management, and prepare for its consequences well in advance."

    A recent study led by researchers from the National University of Singapore (NUS) has found a clear link between the color of a taxi and its accident rate. An analysis of 36 months of detailed taxi, driver and accident data from two fleets of yellow and blue taxis in Singapore suggested that yellow taxis have fewer accidents than blue taxis. The higher visibility (能见度)of yellow makes it easier for drivers to avoid getting into accidents with yellow taxis, leading to a lower accident rate.

    The study was led by Prof Ho. To test whether there was a causal relationship between the color of a taxi and the number of accidents the taxi had, the research team analysed data collected by the largest taxi company in Singapore. The researchers found that yellow taxis have about 6.1 fewer accidents per 1,000 taxis per month.

    The researchers also studied the economic effect of changing the color of the entire fleet of taxis to yellow. The Singapore taxi company involved in the study owns about 16,700 taxis in a ratio(比例) of one yellow to three blue taxis. If a commercial decision is made to switch from blue to yellow taxis, 76.6 fewer accidents would occur per month or 917 fewer accidents per year. Assuming an average repair cost of $1,000 per car and a downtime of six days, switching the color of all taxis to yellow could produce an annual savings of $2 million.

    "We are eager to continue to validate(证实) the findings of our study by looking at the use of yellow in other types of public transport, such as school buses. For instance, we hope to compare the accident rates of yellow school buses against other colors to find out if yellow is indeed a safer color for school buses. Besides, we are also interested to look at private-hire vehicles and do a comparison of the accident rates of vehicles that are of different colors," explained Prof Ho.

    Chinese high school students who want to enter the University of Cambridge may find that their scores on the national college entrance examination, or gaokao, will help their applications in the future.

    The University of Cambridge said in March that it has been using scores on gaokao as part of its admission criteria (标准) for Chinese students for several years, according to its official Weibo account. In addition to top scores on gaokao, Chinese applicants also need to meet English language requirements, participate in an interview and take a subject-specific wrillcn admission assessment (评估).

    The gaokao has been crillcized by some as a one shot exam that focuses on rote learning (死记硬背) rather than creativity. However, more and more people believe that there's no perfect predictor (侦测指标) of academic performance, and gaokao has the advantage of being what educational experts call a criterion-referenced (标准参照) exam—tests when her students are able to master a given body of knowledge , as well as their ability to work hard and consistently. Recent years have seen more and more foreign universities begin to accept gaokao scores as part of the application process.

    Despite the gaokao's growing acceptance among US universities, "There is a long way to go before the US education circle fully recognizes the gaokao, as there are still many US universities that don't accept it as part of their application process," Chu Zhaohui, a researcher from the National Institute of Education Sciences, told the Global Times.