Human’s appetite for sand could increase 45 percent within four decades, according to researchers who say unchecked consumption risks environmental damage and shortages of a key material for urban expansion. Growing demand for building sand — which is used to make concrete, glass and other vital construction materials – has already seen the rise of sand pirates (盗贼) , with dozens of islands disappearing in Indonesia as a result of casual mining.

Xiaoyang Zhong at Leiden University and his colleagues have calculated that global building sand demand will jump from 3.2 billion tonnes a year in 2020 to 4.6 billion tonnes by 2060. The figure is based on a central situation of future population rises and economic growth, and modelled using estimates of concrete and glass consumption, and the floor area needed in buildings.But there is no reliable estimate for remaining sand reserves, so it is unclear if the world can bear such a big increase. “Sand, and the sand crisis (危机), has been overlooked, creating severe environmental and social consequences. If we don’t act now, we may not have enough sand to develop our cities,” says Zhong.

However, Zhong’s team found that about half the projected consumption in 2060 could be avoided if countries take a suit of measures, including extending the lifetime of buildings, reusing concrete, creating more lightweight building designs and using other materials, such as wooden frames. According to the model, the single biggest reduction in sand use could come from more efficient (有效的) use of space: distributing less floor space per person in buildings, sharing offices, and so on. “It’s hard to say how realistic these measures are. But we want this to happen,” says Zhong.

The research only looked at sand used for glass and concrete in buildings, so is an underestimate of total future demand. Granular data on sand consumption for the 26 world regions studied is also lacking, and not detailed enough for country-level breakdowns.

Failure to act will add existing environmental pressures on reserves of sand in lakes and rivers first, but absolute shortages shouldn't be overlooked, says Zhong. “It would be very questionable if this growing demand could be met,” he says.

A recent study shows that more than 90% of adults report hearing earworm songs on a weekly basis. They can't walk into their office without Rihanna's voice singing “work, work, work” in their mind. That was commonly known as earworm songs — those sticky tunes that continue to play in their heads.

Luckily, most people report earworm songs as pleasant. But others find them annoying or even maddening. “Some people are troubled by them to the point that it disturbs life,” says Elizabeth Margulis, a professor who has studied earworm songs.

Margulis says earworm songs tend to have some predictable characteristics. For one thing, they tend to be small parts of a song — not the whole track. And “the songs you've heard recently also have the most possibility to get stuck in your memory,” she says.

But sometimes something strange and unpredictable can also start a track playing in your head. “Once I was at the doctor's office and saw a poster of a man who I thought looked like Gaston — a character from Beauty and the Beast,” Margulis recalls. A couple minutes passed, and she realized she couldn't get “Be our Guest”, the song in the movie, out of her head, even though she hadn't thought of the tune in years. In that instance, she was able to identify what touched of her earworm: the Gaston-looking man in the poster. “But the connections can be really unclear,” she says.

Margulis points out that, in all of human history, recorded music is a very new phenomenon. She says some have inferred that earworm songs are also new — the unintended consequence of being able to hear the same song played everywhere in the same way over and over again. So far, the convincing explanation for why human beings experience earworm songs remains a mystery. But there are some well-established ways to cast off the earworm songs.

“Finding a mentally demanding task and putting your mind on it usually shifts attention away from internal music. People tend to get earworms when performing tasks that don't require their full attention — stuff like doing the dishes,” Margulis says.

Chewing gum can also help. When a song is stuck in our heads, it's almost like we're singing along with it. If you make your mouth do something else — chewing gum, eating a meal or talking with a friend — that can kick out the earworm.

You could also face your enemy. By listening to the full track that includes the passage stuck in your head, you may find “closure” and relief.

When you try a new restaurant or book a hotel, do you consider the online reviews? Do you submit online reviews yourself? Do you pay attention if they are filtered (过滤)? Does that impact your own online review submissions?

In 2010, Yelp shared a video to help users understand how its review filter works and why it was necessary. In recently published research, T. Ravichandran, Ph. D. from Rensselaer Polytechnic Institute, and his team compared reviews of over 1,000 restaurants on Yelp to those same restaurants on TripAdvisor, which did not openly share its review filter policies. They found that the number of reviews submitted to Yelp decreased. Those submissions were increasingly negative and shorter in length compared to TripAdvisor. Also, the more positive a review, the shorter it was.

“Platforms are pressured to have content guidelines and take measures to prevent fraud (欺诈) and ensure that reviews are reliable and helpful,” said Ravichandran. Platforms use advanced software to flag and filter reviews. Once a review is flagged, it is filtered out and not displayed, and it is not factored into the overall rating for a business. “However, most platforms do not openly disclose their policies, leading consumers to suspect that reviews are controlled to increase profit by filtering so-called dishonest content,” Ravichandran added.

Whether or not to disclose review filters is a critical decision for platforms with many considerations. Users may put less time and effort into their reviews if they suspect that they have a significant chance of being filtered, or they may do the opposite to make their reviews less likely to be filtered. Since most false reviews are overly positive, users may assume that positive reviews are most likely to be filtered and act accordingly.

“Review moderation(审核) openness comes at a cost,”said Ravichandran. “Although openness helps to position a platform as fair toward advertisers, the resultant decrease in the number of reviews submitted impacts the platform’s usefulness to consumers.” Online reviews pose great opportunity for firms, but also raise complex questions. Platforms must earn the trust of users without sacrificing engagement.