Here on Earth where most of us live, we spend about a third of everyday lying down sleeping and two-thirds standing or sitting in an upright position.

That's not really how it goes in space when people are weightless and the zero gravity environment causes more liquid to shift to the head. Faces get swollen, legs lose volume and appear to be smaller. Many astronauts have complained of eye and back problems after coming back down to Earth and its gravity.

And now scientists say they have discovered some new risks with long-term space flight. A study published recently in JAMA Network Open, a medical journal, examined 11 healthy astronauts who had been on the International Space Station for six months. Eight of them had unusual characteristics observed in their blood. For instance, six of the astronauts had reverse （反向的）blood flow from their heads.

The lead author of the study says he doesn't know if that's actually harmful. The blood is still leaving the head from other pathways, so flowing backwards through a jugular vein（颈静脉） may not be dangerous. But he says it does show a change in how blood moves through the body while in space.

Another issue the study found was blood clots （凝块）. One astronaut had one. Another showed signs of a partial blood clot. That is potentially harmful as the clots can block the flow of blood to the lungs. The astronaut who had one was treated for the rest of the spaceflight and made it home safely.

What does all this mean? Well, one researcher says these issues have probably been oc- curring since humans first went into space and that they would likely resolve themselves when astronauts came back down to Earth. Knowing about them now gives doctors something else to monitor when people leave our atmosphere.

The government of Singapore has created a highly developed system that turns wastewater into drinking water. The system involves a network of tunnels and high-technology treatment centers.

Reused wastewater can now meet 40 percent of Singapore's water demand. The country's water agency says it expects to meet 55 percent of Singapore's water demand by the year 2060. Most of the water is used for microchip manufacturing centers and cooling systems in buildings. But some of it is added to the country's drinking water supplies. The system helps reduce ocean pollution, as only a small amount of the treated water is sent into the sea.

The United Nations estimates that 80 percent of the world's wastewater flows back into the oceans without being treated or reused. Singapore has few natural water sources. The island nation has long had to depend mostly on supplies from neighboring Malaysia.

Low Pei Chin is chief engineer of the water reclamation department of the Public Utilities Board. She told reporters with Agence France-Press, "Singapore lacks natural resources, and it is limited in space, which is why we are always looking for ways to explore water sources and stretch our water supply." One major plan is to "collect every drop" and "reuse endlessly," she added.

The Changi Water Reclamation Plant on Singapore's eastern coast is the main part of the country's recycling system. Parts of the water treatment center are underground. Wastewater enters the center through a 48-kilometer tunnel that is linked to sewers. The center contains a large system of steel pipes, tubes, tanks, cleaning systems and other machinery. It can treat up to 900 million liters of wastewater a day. In one building, a network of air flow systems has been put in place to keep the air smelling as fresh as possible. Waste that arrives at the plant goes through a cleaning process before powerful pumps send it flowing to areas above ground for more treatment.

There, the treated water receives additional cleaning. Bacteria and viruses are removed through highly developed cleaning processes and disinfected with ultraviolet radiation.

Singapore is also in the process of expanding its recycling system. The country will add another underground tunnel and a major water treatment center to serve the western half of the island. Officials expect work on the center to be completed by 2025. By the time the expansion is finished, Singapore will have spent about $7.4 billion on its water treatment systems.

The health benefits of gardening

Someone argues that it wastes trouble and time to plant and grow things just for some vegetables and flowers. However, it offers us a lot. 【小题1】 There are also more advantages.

It’s a fun workout. It’s wonderful to get out in the garden on a beautiful day. Planting seeds, pulling up weeds and other gardening tasks actually provide a whole-body workout for adults over 65 years old. 【小题2】 Thus, it might keep your interest longer than traditional exercise.

It sharpens your mind. 【小题3】 Researchers once measured the part of brain related to memory and found the participants, all seniors, had their levels of memory increased greatly after they created a vegetable garden.

It benefits your heart and weight. Gardening can contribute to reducing the risk of a heart attack by 30 percent. That is because “playing in the dirt” helps reduce stress. In addition, one goal of doing exercises is to stay in shape. 【小题4】 According to an American research, gardeners have a significantly lower the risk of being overweight or obese than non-gardeners.

【小题5】 An experiment conducted by NASA found that planting and nurturing seeds improved astronauts’ moods and eased their stress in the outer space. Since gardening can do that for astronauts, it can also benefit us.