1 . Have you ever got the thought or feeling that you’re being watched? Well, guess what? You might be right.

According to a study published in Nature on June 23, astronomers have found that 1,715 stars have had a direct view of Earth since humans have been here.

In order to do this, scientists used a previous method that looked for life on other planets. But instead, they changed the method so it could try to determine what places could see us.

The team looked at 331,312 stars within 326 light-years of Earth, with each light-year equaling 9.4 trillion kilometers. Out of all those stars, only 1,715 of them could see Earth within the last 5,000 years, with an extra 319 stars that will be able to see us in the next 5,000 years.

“When I look up at the sky, it looks a little bit friendlier because it’s like, maybe somebody is waving,” said Lisa Kaltenegger, director of the Carl Sagan Institute (研究所) at Cornell University, US, and the study’s lead writer.

If a planet circling around one of those 1,715 stars is home to advanced life, they could easily see that there is life here because of the oxygen on Earth. If that didn’t give it away, then the radio waves we have sent out into space would also be an indicator (标志). In fact, human-made radio waves have already traveled through 75 of the closest stars on Kaltenegger’s list.

Why haven’t we heard from anyone yet, then?

It takes a long time for messages to travel between star systems. By the time a message could be received, that advanced civilization (文明) would probably not exist anymore.

Alan Boss, a scientist at the Carnegie Institution for Science in the US who wasn’t part of the study, wrote in an email that this long time would limit the chances for different life to exchange “emails and TikTok videos”.

“So we should not expect aliens to show up anytime soon,” Boss said.

1. Which word can best describe Lisa Kalteneggers’ attitude towards the sky that he looked up at?

A．Objective

B．Indifferent

C．Critical

D．Positive.

2. What does the underlined word “that” in paragraph 6 refer to?

A．The oxygen on Earth.	B．Human-made radio waves.
C．Advanced life in other planets.	D．A planet circling around one of those 1,715 stars.

3. What could prevent humans from exchanging messages with aliens according to Boss?

A．Aliens don’t exist.	B．They cannot understand each other.
C．It takes a long time for messages to travel.	D．Human-made radio waves cannot travel far.

4. What is the purpose of the text?

A．To present new findings published in a study.

B．To raise readers’ interest in aliens and the universe.

C．To discuss if there is advanced life on other stars.

D．To explain how messages travel between different star systems.