What will astronauts eat when a space trip takes years?

“Lots of fresh vegetables,” says Dr. Janet Williams, whose team have spent the last 10 years learning how to grow plants in a space station. And it’s a good thing that she has already started her work, because space gardening can be really hard.

As usual, astronaut George White looked into the closed plant room. He had planted Dr. Williams’s quick-growing seedlings none of the stems were showing. He opened the room to check and found the problem. The stems weren’t growing upward and the roots weren’t growing downward. On Earth, gravity (重力) helps a plant’s stems and in it, but roots (根) to find “up” and “down”. However, in the space station, there was almost no gravity.

Dr. Williams suggested a method: give the plants more light, as plants also use sunlight to find their way. And it worked. When the plants had more light, the stems turned up and the roots went down.

Now Dr. Williams was free to worry about the next problem: Would her baby plants live to flower? Can we grow food on a space journey?

Many plants died in the space station. Dr. Williams thought she knew why: the space plants were hungry for air. Plants live by taking up CO₂ from the air. Since a plant uses it up in the air around, the plant needs moving air to bring more CO₂ close to its surface! On Earth, the air is always moving. Gravity pulls down cold air, and warm air rises. And with these air movements, plants get enough CO₂.

Many earlier experiments (实验) with plants in space had used closed rooms. Dr. Williams tried a new greenhouse that had a fan (电扇) to keep the air move. The plants loved it. They flowered and even produced more seeds. Using Dr. Williams’s method, astronaut George completed the first seed-to-seed experiment in space, and moved one plant closer to a garden in space.

“And this,” says Dr. Williams, “is good news for long-term space travel.”

The journey into space is a long and dangerous one, and not many people are able to do it. Lots of training is in need before one gets on the spaceship. But soon, it may be as simple as riding an elevator.

A group of Japanese scientists from Shizuoka University have been working on a “space elevator”, which will allow easy access to space.

On Sept 22nd, 2018, two tiny satellites were sent to the International Space Station（ISS）as a test for the space elevator. The mini elevator has a 10-merer steel cable. It works as a tiny model of a full-size “space elevator”, which might reach from Earth all the way to outer space. “It’s going to be the world’s first experiment to test elevator in space,” the spokesman of Shizuoka University said.

According to Science Daily, the research team hopes to build the elevator by 2050. The space elevator may be able to carry up to 30 people. The trip will be about 36,000 km, which will take around eight days to complete. If it is successful, space elevators will greatly cut the cost of transporting cargo into space from $22,000（154,000 yuan）to $200（1,400 yuan）per kilogram. More importantly, they will produce less pollution during spree travel.

Still, there are many hurdles along the way. According to the official website of the US-based Smithsonian Institution, until now, researchers haven’t found a material strong enough to hold the stress placed on the elevator cable. Even carbon nanotubes, the strongest material they have found so far, would break under the stress.

The challenges facing the space elevator are massive, but they have not stopped Japan from working on it. “Japanese researchers believe the idea of space elevator will be realised. since there are many scientists in the fields of robotics and carbon nanotube technology in the team,” Michelle Z. Donahue, Smithsonian science reporter, wrote in 2016.

In many science fiction (科幻) movies, men travel to faraway stars and even fight with aliens. But are there real aliens in the universe (宇宙)? The answer of some scientists is yes. So they have been searching for aliens in outer space for many years. They hope io find life signs of aliens.

Some scientists are used to using radio telescopes (望远镜) to search for aliens in space. In order to find aliens, they have worked hard for over half a century, but so far they have found nothing. Then some scientists guessed aliens might not want to connect us, but aliens could answer our messages. So some scientists sent radio signals into the universe. They hope one day they would be picked up by alien technology. These scientists want to prove (证明) that we are not alone in the universe.

But what should we do if the “alien phone” rings one day? Should we answer it? Stephen Hawking, the famous physicist, thought it could be dangerous to connect aliens. He said that the main purpose of aliens’ visiting to our solar system could be searching for our resources (资源). But other scientists think we have no need to worry. David Morrison. a NASA scientist, said, “If an alien radio signal reaches the earth from a planet thousands of light-years away, then they almost surely have solved all the problems we still have including the short of resources. Maybe they are much smarter than us, but why don’t they hurt us? I think we can try to connect them.”