【推荐3】Telescopes（望远镜）have come a long way since the first ones were invented early in the 17th century.Traditional telescopes allow astronomers to view objects in space thanks to the visible（看得见的）light those objects emit（发出）, or reflect.However, for modern telescopes, any Electromagnetic（电磁的）radiation will be enough for the purpose of viewing objects in space.Extremely hot objects, such as stars, emit not only visible light but also high-energy gamma radiation.Specialized telescopes—such as NASA's space-based Chandra X-ray Observatory—are built to detect such radiation.Cold objects—like comets and asteroids—emit low-energy radiation, which is invisible to the naked eye.Much of the universe is even colder.The clouds of dust and gas of which stars are made are only slightly warmer than absolute zero—the temperature at which atoms stop moving.To catch images of cold objects, astronomers use radio telescopes.

A radio telescope is a device that typically uses a large dish antenna（抛物面天线）to collect the low-energy radiation emitted by objects in space.However, it was quite challenging to get a clear image of those objects using ground-based antennas.The reason is that low-energy radiation is absorbed and distorted by water vapor（水蒸气）in the Earth's atmosphere.The signal that a dish antenna on the ground finally receives is therefore weak.

The signal can be strengthened by positioning the antenna on a site with very dry air.It can be made even stronger by arranging several antennas in an array, combining their signals so that they function together as a single, more powerful telescope.And if the antennas are portable, the distance between them can be adjusted to change the sensitivity of the telescope.Placed far apart, they can focus on a small goal, such as a planet.Grouping the antennas closer together can be useful for catching images of an object as large as a galaxy.

Atacama Large Millimeter Array（ALMA）, a large array of antennas, was officially opened in March 2013.Since the official opening of ALMA, there has been a steady stream of discoveries of great interest to astronomers.In July 2013, the telescope's high-quality images provided clues that may help answer a question that has long puzzled astronomers.ALMA is also helping researchers understand how planets are born, by providing the first-ever images of the planet-forming process.These observations are just the beginning.In the future, ALMA will show us even finer details of galaxies and star systems.

【推荐1】This is the moment a harpoon (鱼叉) was fired in space striking a target almost dead centre. It was filmed 400km above the Earth. It’s the latest experiment from the Remove DEBRIS spacecraft. Led by Surrey University, it’s a mission that’s testing out the technologies that could clean up space junk. It was absolutely a success. And the goal of the experiment was to hit the target.

There are approximately 23,000 pieces of debris (残骸) larger than a softball orbiting the Earth. They travel at speeds up to 17,500 mph, fast enough for a relatively small piece of orbital debris to damage a satellite or a spacecraft. Much more debris—too small to be tracked, but large enough to threaten human spaceflight and robotic missions—exists in the near-Earth space environment. Since both the debris and spacecraft are traveling at extremely high speeds, an impact of even a tiny piece of orbital debris with a spacecraft could create big problems.

In 2016, the crack in the window of the International Space Station was thought to have been caused when a tiny bit of paint hit it. Larger objects could do even more harm. Scientists are particularly worried about a European satellite the size of a double-decker bus that stopped working in 2012. It’s now threatening other satellites in its path and needs to be removed from its orbit.

Last year, the Remove DEBRIS spacecraft tested a net, proving it could catch a passing satellite. It’s the first mission to try and address this problem. And it’s also used its on-board cameras to track a rolling target—essential for hunting down any casual space litter. Its final test will be in the coming weeks. It’s set to bum up as it returns to Earth, preventing it from becoming a piece of space junk itself.

The hope is now that future missions can be scaled up so the celestial (天空的) deep clean can begin.

【推荐3】Are your childhood memories closely connected with cycling? Perhaps you even remember the pride in getting your first bike on your birthday, complete with streamers (装饰彩纸条) coming out of the handlebars, and the excitement of coasting down the tallest hill in town? When we were children, biking gave us independence, a sense of self, adventure and excitement, but city biking poses challenges to us when we are adults.

Obviously, biking brings a number of benefits to the riders, but why aren’t there more bikers on city roads? Goodordering, a company that designs bags to suit modern active lifestyles, conducted a survey and found out that the number one factor preventing people from biking to work was the realization of road safety”—sharing the road with cars can be dangerous.

Omar Bakhshi, a UK-based developer, experienced this first-hand. A car brushed against him while he was cycling, leaving him with an injury that impacted his taste and smell for life. Bakhshi realized what happened to him wasn’t unusual. Because bikers often experience close encounters (相撞) with cars, Bakhshi set out to make the roads safer for urban cyclists to use.

His company, Tether, is launching a small sensor that goes on a bike’s handlebars. As the biker rides through the city, the device projects (投影) a “safety zone” of lights onto the pavement. The hope is that these lights will force car drivers to sit up and pay attention to the rules of sharing the road. If cars get too close to the biker’s personal space, the lights will start shining.

What makes Bakhsh’s device different from similar devices on the market is its smart features. Tether’s device collects data from close encounters with cars and then the data is organized into a central database. The data can be accessed by bikers to determine which streets are safer for cyclists and choose a route to avoid areas that have a large number of close encounters with cars.