【推荐1】It was an innocent little detail, backed by centuries of science, in a chemistry book about tea, something American author Michelle Francl never anticipated would cause a stir among the British.

In her new book, Steeped: The Chemistry of Tea, Francl analyzed caffeine levels and studied the molecules that give tea its good smell. She uncovered the little-known presence in tea of other chemicals, including fluoride and aluminum. And she also mentioned a careful study of an 8th-century Chinese article that called for salt to be added to the boiling water.

“The sodium ions (钠离子) in the salt block our sense of bitterness,” says Francl, a chemistry professor at Bryn Mawr College in Pennsylvania. “So if you put a tiny bit of salt in — not enough to taste — you make the cup of tea or coffee smoother and less bitter.”

The recipe for a perfect cup of tea, she wrote in her book, includes a little salt. And for tea with milk, Francl recommends warming the milk first, so that it doesn’t curdle (凝结) when it hits the hot water.

Sounds harmless, right? But anyone with British friends and loved ones — or who’s spent more than five minutes in the United Kingdom — will know that recipe amounts to blasphemy. Within hours of the publication of Francl’s book, face palm emojis (捂脸表情) were appearing across the British Isles.

“Hot milk and salt!? Who is this person?” radio host Toni McDonald shouted on his program.

“This scientist supposes that the only way to have a decent cup of tea is with a little salt? That’s foolish!” another radio host, Vic Minett, said.

To respond to these complaints, the U.S. Embassy’s public affairs officer, Rodney Ford told the press, “We want to say to the good people of the U.K. that the unthinkable idea of adding salt to Britain’s national drink is not official United States policy — and never will be.”

【推荐2】Types of Maps

Different types of maps have different uses. Tourist maps, for example, have signs to show places of interest in an area. When tourists read these maps, it is easy for them to find where to go and what to see in a place and it is easy for them to go and find their ways to these places.

Road maps show large areas so that people can plan long journeys. Different types of roads are given different numbers. For example, if you want to go to Wood Green, you just follow No. 621 Road and keep looking at the road signs.

Distribution maps use colors or signs to show facts about an area. For example, where different languages are spoken, how many people live in an area, how cold and hot some places are, or whether a place is short of water.

Some maps, such as railway maps, use straight lines to show everything. This is easy for people to read. Trains are fast. People don’t have to think about small places they go past. They just need to know the two ends of their trips.

【推荐3】If you live in one of the 40 million American households with a gas stove, it could be leaking even when it’s turned off.

According to a new study from Stanford scientists, many stoves are constantly giving out gases that can warm the planet and pose serious health risks when breathed in. The research found methane missions from gas stoves across the United States are roughly equal to the carbon dioxide released by half a million gas-powered cars in a year.

To estimate the impact of these emissions, researchers measured three key gases from stoves in 53 homes across seven California counties. The team chose two gases — methane and carbon dioxide — because of their contribution to climate change, and selected nitrogen oxides because of their known risk to human health. The scientists set up plastic dividing walls between the kitchens and other rooms and used instruments that measure wavelengths of light to determine the concentration of certain gases.

The team estimated that stoves release between 0.8 and 1.3 percent of the natural gas they consume as unburned methane. To their surprise, they found that more than three-quarters of the methane emissions happened when both old and new gas stoves were turned off. “Over a 20-year time scale, the global warming potential of methane leaks is 86 times greater than carbon dioxide,” Stanford reports.

The most significant health risks happen when the stove is lit, the authors note, because the process creates nitrogen dioxide as a byproduct. Increasing airflow by using a range hood can help reduce the personal health risk of natural gas-burning appliances, but most individuals report rarely using their ventilation system.

In a small kitchen, it only took a few minutes of unventilated stove use to generate emissions levels above national health standards. According to a meta-analysis from 2013, children living in homes with gas stoves were 42 percent more likely to experience symptoms associated with asthma, and 24 percent more likely to be diagnosed with lifetime asthma.

In addition to health risks, natural gas burning stoves also endanger the planet by releasing methane. The results of the study have furled efforts by scientists and activists to encourage Americans to switch to all-electric stoves and appliances.