BEIJING, March 14 (Xinhua) -- When the news of legendary physicist Stephen Hawking's death broke Wednesday morning, Gou Lijun thought it was just a rumor again.

"Every time he turned out to be fine. I've always thought he would live on, in his wheelchair, smiling, for a very long time. I was astonished to learn it was true," said Guo, a researcher at the National Astronomical Observatories of China.

The British physicist has died at the age of 76, a family spokesperson announced Wednesday.

Hawking, a towering figure in the modern history of physics, authored several science best-sellers, including "A Brief History of Time," despite becoming wheelchair-bound a few years after being diagnosed with a motor neuron disease in 1963.

Hugo Award-winning author Liu Cixin expressed his grief over the death of Hawking.

"There are people who can only flicker their eyelids, but their thoughts may travel far into space. There are those whose bodies are robust and strong, but their minds are weak, and they are destined to live their entire lives dependent on others," the science-fiction writer said.

In the end of one of Liu's short stories, Hawking, on behalf of humankind, asks the ultimate question to an alien: "What is the purpose of the Universe?"

No answer appears in the sky. The smile on the alien's face disappears, and a flash of unnoticeable panic occurs in his eyes.

Liu, author of "The Three-Body Problem," was the first Asian writer to receive the Hugo Award for Best Novel, the top sci-fi award, in 2015.

Liu considered Hawking a legendary scientist.

"He has fought serious illness for a long time to obtain outstanding achievements in physics -- in particular, the studies on black holes and cosmology," said Liu.

Liu especially admired Hawking's charm and personality.

"He is very different from other scientists. He went through more hardships than most scientists," Liu added.

Tributes also began pouring in from netizens on Hawking's account on Chinese microblog Weibo.

In his last post published on Nov. 24, 2017, the physicist presented a video response to a question about life beyond Earth from Wang Junkai, the lead singer of TFBOYS, China's most popular boy band.

The post has received more than 70,000 comments and 217,000 "thumbs up" so far. Nearly 1,000 comments were posted on Wednesday, followed by emojis such as candles, praying palms and crying faces.

"A giant in a wheelchair and a great physicist for the world, Hawking has written his legend with a strong spirit," commented "MrZhouningbo" on Weibo.

Hawking opened the account in April 2016, which attracted 1.3 million followers in just 8 hours and grew to over 4.6 million followers.

"Greetings to my friends in China! It has been too long!" his first entry said.

Hawking said his first trip to China was in 1985, when he traveled across the country by train.

"In my physical travels, I have only been able to touch the surface of your fascinating history and culture," Hawking said in the post, using the signature S.H. to indicate he was personally making the entry.

Stories and features about him also went viral on WeChat.

"Hawking just left his wheelchair and flew to the stars," commented a netizen named "Guangyan."

"He just entered another space -- may he rest in happiness," said another WeChat user named Daiyu.

(Ji Shaoting and Qiu Mengyang contributed to the story.)