On April 2，we said goodbye to Tiangong I，China’s first space lab．According to the China Manned Space Agency（中国载人航天），Tiangong I re-entered the Earth’s atmosphere (大气层) and fell into the South Pacific Ocean.

There are many spacecraft that are still in orbit above the Earth．They are flying at heights ranging from 300 to 1，000 kilometers．After finishing their trips，they will all re-enter the Earth's atmosphere like Tiangong I．

There are two types of re-entries：controlled（受控的）re-entry and uncontrolled re-entry．

Some satellites（卫星）and manned spacecraft come back to the Earth in a controlled re-entry．Scientists calculate（计算）the path of the falling spacecraft and its speed．They can guide the spacecraft to fall in a chosen area．In 2017，Tianzhou I，China's first cargo（货运）spacecraft，was directed to fall in the South Pacific Ocean．

Some spacecraft may have problems while in space，or are simply no longer usable after a certain amount of time．These craft come back in an uncontrolled re-entry．It is hard to tell when and where these spacecraft will fall until the last few hours．The US space station Skylab came back partially uncontrolled in l979．Parts of the station fell in western Australia，but no one was injured．

During re-entry，most of the spacecraft will burn up while passing through the Earth's atmosphere．Only a small amount of the debris（碎片）will reach the ground．

The debris typically ends up falling into the ocean，China Daily reported．Tiangong I weighs about 8.5tons．The amount of debris that falls to the Earth might be about l to 1.5 tons， the Beijing News reported． That is about the same weight as a car．

For hundreds of years, researchers have been trying to answer what kinds of things have an impact on people’s emotions（情感）. How you feel is controlled by many things. Your emotions can be influenced by your personality, by the actions of others and by events around you. In addition, maybe you really don’t know your emotions can be affected by the weather as well.

People often say they feel pretty good when the sun is shining and bad when it is cloudy.

As a matter of fact, sunlight makes us feel good. When sunlight shins our skins, our bodies produce a vitamin. Vitamins are natural chemicals (化学物质) which we all need to stay healthy. Sunlight helps our bodies produce vitamin D and it can help our bodies to make a special chemical. This special chemical affects our brains(大脑) and makes us feel happy.

For example, there are long, dark winters of little sunlight in Sweden and Norway, so many people in these countries often feel sad. Without much sunlight, their bodies produce less vitamin D. Without enough vitamin D, their bodies make less of this special chemical which makes them feel good.

In order to help the people in these countries feel better, special “sunrooms” with artificial(人造的) lights have been built. People can go there and get “sunlight” for an hour or two!

The weather can also affect people’s emotions in other ways. Hot weather can make people angry because people feel uncomfortable when they are hot. In the same way, rain can make people angry because being wet can be unpleasant. As you can see, the weather can have an effect on the chemicals which control our brains. Through these ways, the weather can influence our emotions. Sadly, while the weather can change us, we can hardly change the weather.

A major new facility to pull CO₂ out of the atmosphere has started operating in Iceland, which is a boost to an emerging technology that experts say could eventually play an important role in reducing greenhouse gases.

The plant in southwest Iceland is the biggest of its kind, its builder says. It is able to capture 900 tons of CO₂ every year but it needs heat and electricity to work. It is using energy produced from waste and is built on the roof of a waste incineration plant, and through the burning of rubbish, energy is generated.

Human-sized fans are built into a series of boxes. They take CO₂ out of the air, catching it in spongelike filters (过滤器). The filters are blasted with heat, freeing the gas, which is then mixed with water and pumped deep into deep underground basalt caves, where over time it turns into dark-gray stone. Pumping CO₂ into the ground is just one way to deal with it. The makers are also selling the gas to be used again. The CO₂ can be captured just a few 100 miles away. It is pumped through an underground pipeline directly into a greenhouse. Vegetables and plants love CO₂ and higher concentrations of the gas within the greenhouse improve the growth of plants.

By 2050, humanity will need to pull nearly a billion metric tons of CO₂ from the atmosphere every year through direct air capture technology to achieve carbon neutral goals, according to International Energy Agency recommendations. The plant in Iceland will be able to capture 4000 metric tons annually — just a small amount of what will be necessary, but an engineer in Climeworks, the company that built it, says it can grow rapidly as efficiency improves and costs decrease.

“This is a market that does not yet exist, but a market that urgently needs to be built,” said Christoph Gebald who co-founded Climeworks. “This plant that we have here is really the blueprint to further increase the size and really industrialize.”