【推荐1】The US space agency NASA has revealed an astonishing picture revealing new secrets of the Earth’s home galaxy (星系), the Milky Way. The sun is just one of hundreds of billions of stars that form the huge shape of our galaxy. Our solar system sits in an outlying region but the new image focuses on the centre of the Milky Way, a “noisy” area because of all the crowded stars. Light from this region takes about 26,000 years to reach Earth. For comparison, light takes just eight minutes to reach us from the sun.

The researchers use the data collected by two telescopes that see the sky in ways that are very different from the visible light our eyes can see to form the new image. Most of the data comes from 370 different pictures taken over the past 20 years by NASA’s Chandra X Observatory. This satellite telescope detects X-rays out in space. X-rays are a from of radiation that is sent out when violent events heat matter to temperatures of millions of degrees. Other data comes from the MeerKAT telescope in South Africa, which can detect radio waves from space. These waves have much less energy than X-rays. They are usually produced by cooler material, such as huge clouds of gas between the stars.

The brightest sources include neutron stars which are the cores of huge stars that ran out of fuel and collapsed to city-sized balls of super hot matter. Many neutron stars and black holes jet out gases that appear in the picture as purple streaks (斑纹). Powerful magnetic fields in the area cause the jets to bend as they get further from their source. Astronomer Dr Daniel Wang, who has worked on the image over the past year, said the new picture described “a violent or energetic ecosystem”.

【推荐2】The elements other than hydrogen and helium （氮气）exist in such small quantities that it is accurate to say that the universe somewhat more than 25 percent helium by weight and somewhat less than 25 percent hydrogen.

Astronomers have measured the amount of helium throughout our galaxy （星 系）and in other galaxies as well. Helium has been found in old stars, in relatively young ones, and in the distant objects known as quasars. Helium nuclei have also been found in cosmic rays that fall on the earth （cosmic ‌“rays” are not really a form of radiation; they consist of rapidly moving particles （颗粒）of numerous different kinds）. It doesn’t seem to make very much difference where the helium is found. Its amount never seems to vary much. In some places, there may be slightly more of it; in others, slightly less, but the proportion of helium to hydrogen nuclei always remains about the same.

Helium is created in stars. In fact, nuclear reactions that turn hydrogen to helium are responsible for most of the energy that stars produce. However, the amount of helium that could have been produced in this manner can be calculated, and it turns out to be no more than a few percent. The universe has not existed long enough for this figure to be significantly greater. Consequently, if the universe is somewhat more than 25 percent helium now, then it must have been about 25 percent helium at a time near the beginning.

However, when the universe was less than one minute old, no helium could have existed. Calculations indicate that before this time temperatures were too high and particles of matter were moving around much too rapidly. It was only after the one-minute point that helium could exist. By this time, the universe had cooled sufficiently. But the nuclear reactions that led to the formation of helium went on for only a relatively short time. By the time the universe was a few minutes old, helium production had effectively ceased.

【推荐3】It's our galactic(银河系的) home, but the Milky Way contains many mysteries scientists are working to uncover. Now, as The Guardian reports, astronomers at the European Space Agency (ESA) have built a 3D map that provides the most detailed look at our galaxy yet.

The -data has been seven years in the making. In 2013, the ESA launched its Gaia Space .Observatory from Kourou in French Guiana. Since then, two high-powered telescopes aboard the spacecraft have been sweeping the skies, recording the locations, movements, and changes in brightness of more than a billion stars in the Milky Way and beyond.

Using Gaia's findings, astronomers put together a 3D map that allows scientists to study the galaxy in greater depth than ever before. The data has made it possible to measure the acceleration (加速度) of the solar system. By comparing the solar system's movements to those of more faraway objects in space, researchers have determined that the solar system is slowly falling toward the center of the galaxy at an acceleration of 7 millimeters                           per second per year, The Guardian reports. Additionally, the map shows how matter is distributed (使分配)throughout the Milky Way. With this information, scientists should be able to measure the mass of the Milky Way.

Gaia's observations may also hold clues to the Milky Way's past and future. The data holds small remaining parts of the 10-billion-year-old round flat object that made up the edge of the star system. By comparing it to the shape of the Milky Way today, astronomers have determined that the flat object will continue to increase in size as new stars are created.

The Gaia observatory was launched with the mission of carrying out an updated star census. The previous one was conducted in 1957, and Gaia's new data reaches four times farther and accounts for 100 times more stars.

【推荐1】The Piano Staircase was a project from 2009. This project changes an ordinary stair into a piano. The goal was to see if they could get people to choose the stairs over the escalator (电梯) by making the stairs more fun to do. Researchers set up a subway stair to look and sound like a piano keyboard. These piano stairs will make piano sounds when people walk on them.

Thanks to the project, 66% of the people who passed by took the stairs over the escalators. Walking up and down the stairs is much healthier than taking an escalator. Lately I have been trying to live a healthier lifestyle. I feel it hard to actually make a change without putting effort in it, but small things like taking the stairs can make a difference.

In our country more than 2 out of 3 adults are considered obese for lack of exercise, many of whom weigh over 100 kilograms. We recently have installed (安装) one of these piano staircases at Rotterdam City Station, and it has worked well so far. And for me, it can really lighten up my mood.

The stairs look more fun when decorated as a piano. I love the way these stairs look as it gives the stations a much friendlier appearance. People are attracted to walk on the project and to play with it. Apart from actually encouraging people to take part in the project, it raises awareness for physical exercise. However, there is also the weak side. When you first experience the Piano Stairs, it is exciting, but when you have seen the Piano Stairs several times, it can get boring. As a result, they may start taking the escalators again.

I have seen many people on social media expecting this project to be installed near where they live. And personally, I would love to see more of these Piano Staircases as well, even it is just to cheer me up while traveling.

【推荐2】Chemicals taken from sawdust (锯屑) and water can knock out more than 99 percent of some disease-causing microbes (微生物). That makes the sawdust mix a potential alternative to current microbe-killing chemicals.

Many disinfectants (消毒剂) used today can harm the environment. They form poisonous by-products when they get washed. Some potentially greener disinfectants exist. They rely on a chemical called “phenol (苯酚)”. But these cleaners can be costly and take a lot of energy to make.

Shicheng Zhang went searching for a better option. He’s an environmental engineer at Fudan University in Shanghai, China. Wood contains many molecules (分子) that look like phenol. So Zhang wondered if microbe-killing chemicals could be obtained from sawdust through a low-cost and low-energy process.

He and his fellow researchers cooked mixtures of water and sawdust for one hour. They heated this sawdust soup under pressure, and then filtered it. Later, they tested how well the liquid killed off microbes. This liquid wiped out E.coli bacteria—microbes that can cause food poisoning. The liquid also killed anthrax bacteria. These microbes cause dangerous infections. What’s more, the disinfectant stopped flu viruses from being infectious.

The researchers also added different amounts of water to the sawdust soup. That let them test how concentrated it had to be to knock out microbes. Depending on its concentration, the mix could kill more than 99 percent of the microbes.

Looking at killed microbes under a microscope revealed some of the ways the sawdust mix kills. The disinfectant damaged the microbes’ cell walls. It also may have messed with the microbes’ proteins and DNA.

Zhang and his fellow researchers didn’t stop at a sawdust disinfectant. They made disinfectants from other plant materials, too. Some of these started as bamboo powder. Others were made using rice plant. Plant materials that are richer in molecules that release phenol-like compounds are best at killing microbes. One example is corn straw.