On March 14, one of science's brightest stars went dark. Stephen Hawking, the world-famous British scientist, died at 78 in Cambridge, UK.

    Hawking is considered by many to be the greatest scientist in history since Albert Einstein. He came up with the theory（理论） that the universe (宇宙) began with the Big Bang and will end in black holes. His theories became the base for a lot of later research. He also wrote books to help common people understand the universe. His most famous book is A Brief History of Time, which has sold more than 10 million copies around the world.

    Besides his scientific achievements, Hawking was also someone who had a strong will. When he was 21, he got a serious illness that stopped him from walking and talking. Later in life, he had to sit in a wheelchair and “speak” using a computerized voice. But this didn't stop him from living a meaningful and colorful life.

    He celebrated his 60th birthday by going up in a hot-air balloon; when he was 65, he took part in a zero-gravity (零重力) flight to experience weightlessness. He hoped to travel into space one day. In 2015, Hawking spoke about how he felt life was unfair when he first knew about his illness. “But now, 50 years later, I can be quietly satisfied with my life,” he said.