Our sun is a star, and nine worlds (天体) move round it. Worlds like these are planets. But here are other stars, other suns, not only thousands of them, but millions of them. Do different stars have planets? We can see the planets round our own sun. But we haven't been anymore. The stars are too far away from us. Stars give out light, but the planets don't have any light of their own. So we can't see them. They are too far, and too dark. Still, we can tell that some stars have planets. While a big planet goes round, it pulls its star to one side. And sometimes we can see this. Then we know that the star has a planet. For example, Barnard's Star is a small red star. And it is the quickest star in the universe. But sometimes it moves slower, and then quicker again. We have known Bernard''s Star for many years, and now we are sure it has a planet.

    Today is December 15, 2030. Influenced by the launch of the first manned mission to Mars next month, you will most likely get a gift card for a space trip.

    The interest in trips, 100km above the surface of the Earth, has grown steadily since such a trip began. However, the market has grown much larger this year since the official announcement of the Mars mission. More low - cost spacelines have entered the market and you can now find flights for such a trip for as low as $3,495.It's very reasonable.

    Space tourism( 旅游业，观光业) is one of the markets that have developed fast during the last decade, with the opening of the Starbright Hotel on the moon as well as the low orbital hotels that started accepting guests. However, accommodation in space is still expensive for the average household, so the suborbital (亚轨道的) flights with thirty - minute weightlessness during the three - hour flight will for some time be the most popular trip.

    However, the spacelines might in the future face fierce competition between space elevators (太空升降舱), like the one that is projected to start construction within two years. Once it is fully functional, it will start to ship cargo to space. But it will accept passengers as soon as possible to get back the large investment. Even if the elevator becomes successful, it will take several years before there are more elevators in the world to get in the competition for space traffic with the spacelines.

    Those who are looking for a little bit of adventure and have extra money to spend may want to consider a suborbital flight in space. While a suborbital flight may not be the space mission that you have always dreamed of, it will give you the rare opportunity to see what our planet looks like in a high - altitude flight outside our atmosl3here. So before you enjoy a trip by elevator to space, enjoy a suborbital flight first.

    The world is not hungry, but it is thirsty. It seems strange that nearly 3/4 of the Earth is covered with water while we say we are short of（短缺）water. Why? Because about 97% of water on the Earth is sea water which we can't drink or use for watering plants directly(直接地）. Man can only drink and use the 3%-the water that comes from rivers and lakes. And we can't even use all of that, because some of it has been polluted(污染）.

    Now more water is needed. The problem is Can we avoid（避免）a serious water shortage later on? First, we should all learn how to save water. Secondly, we should find out the ways to reuse it. Scientists have always been researching in the field. Today, in most large cities water is used only once and then runs to the seas or rivers. But it can be used again. Even if(即使）every large city reused its water, there would not be enough. What can people turn to next?

    The seas seem to have the best answer. There is a lot of water in the seas. All that needs to be done is get the salt out of the sea water. This is expensive, but it's already used in many parts of the world. Scientists are trying to find a cheaper way of doing it. So you see, if we can find a way out, we'll be in no danger of drying up.

    A thirsty crow(乌鸦) comes across(偶然遇到) a bottle of water, but the water level is out of its reach. The bird then drops some stones into it and gets the water.

    "It's just a story," you may think. But new research has found that crows' brains may sometimes be better than those of 6­year­old children.

In a recent experiment, American scientist Corina Logan and her team caught six crows to test them. The crows and children had to choose between two sets of tubes(试管). They had to drop stones in and get water.

    With the red set, when they dropped a stone into a wide tube, the water level raised in a connected narrow tube. The blue set of tubes, however, had no connection between them.

    Children aged 7 to 10 were able to learn the rule. Children aged 4 to 6, however, failed. Five of the six crows failed the test. But Kitty, a 6­month­old crow, passed it. She put most of the stones into the red tubes.

    So, could a bird be more clever than a kindergartner? Don't be too quick to say no.

    Is there intelligent (有智力的) life on other planets? For years, scientists said "no" or "we don't know". But today this is changing. Seth Shostak and Alexandra Barnett are astronomers (天文学家). They believe intelligent life exists (存在) somewhere in the universe. They also think we will soon contact these beings (人；生物).

    Why do Shostak and Barnett think intelligent life exists on other planets? The first reason is time. Scientists believe the universe is about 12 billion years old. "This is long enough for other planets to have intelligent life," say Shostak and Barnett. The second reason is size—the universe is huge. "Tools like the Hubble Telescope (哈勃望远镜) have shown that there are at least 100 billion galaxies," says Shostak. "And our galaxy, the Milky Way, has at least 100 billion stars. Some planets going around these stars might be similar to Earth."

    In the past, it was hard to look for signs of intelligent life in the universe. But now, powerful telescopes (高倍望远镜) allow scientists to discover smaller planets. These planets might have intelligent life.

    Have beings from space already visited Earth? "Probably not," says Shostak. However, intelligent beings may contact us in other way, such as radio signals (信号). In fact, they may be trying to communicate with us now, but we don't have the right tools to receive their messages. However, this is changing. By 2025, we could make contact with other life forms in our universe and we might help each other.