SINGAPORE - In the last year of his life, British theoretical physicist Stephen Hawking was working on a book that would sum up his "brief answers to the big questions": How did the universe begin? Is there other intelligent life in the universe? Can humanity survive on Earth?
Hawking, regarded as one of the world's most famous scientists, died aged 76 in March this year before he could finish the book, but it has now been published as his final work by his children and friends.
Brief Answers To The Big Questions, his daughter Lucy Hawking tells The Straits Times over the phone from Britain, is an attempt to respond to the questions he was regularly asked by everyone, from political leaders to the public.
"Putting the book together was almost a comforting thing to do in the aftermath of his passing," says Ms Hawking, 47, a writer. "It was like listening to him talk or having a conversation with him, and then there would be these sudden jolts of reality when you realised he wasn't there any more."
Hawking was the Lucasian Professor of Mathematics at the University of Cambridge for 30 years and the author of numerous books, including the best-selling A Brief History Of Time (1988).
He had a rare early-onset slow-progressing form of amyotrophic lateral sclerosis, a motor neurone disease which gradually paralysed him. He communicated through a speech-generating device which resulted in his iconic computerised voice.
His last book, says Ms Hawking, will follow in the vein of his other popular works, making complex science accessible and engaging to lay readers. "It just draws you through these vast, existential topics with such ease and elegance and humour."
In his essays, he takes on questions such as "Is there a God" (Hawking: "For me... there is no possibility of a creator, because there is no time for a creator to have existed in") or "Is time travel possible?"
Many of the essays bear a sense of urgency, a warning from beyond the grave. He worries about what would happen if super artificial intelligence decided its goals were not aligned with mankind's or if genetic manipulation became the preserve of the rich and powerful, leaving the rest of ordinary humanity in the dust.
He reiterates the need for space missions that will eventually enable humans to leave Earth and find new habitation elsewhere in space.
"He often talked about how people were not taking climate change seriously enough," says Ms Hawking. "Venus is the sister planet to Earth and we risk becoming what Venus is like now - hellishly hot on the surface, dense smoggy atmosphere, rains of sulphuric acid. Venus is a postcard from our future if we don't take some form of action."
She gestures at the landmark report released by the Intergovernmental Panel on Climate Change earlier this month, which laid out the steps political leadership must take to cap global warming at 1.5 deg C above pre-industrial levels, or risk environmental collapse.
One accolade Hawking never received was the Nobel Prize for Physics, which he quips about in the book. A Nobel would require experimental proof of his theoretical work, and nobody has been able to observe a black hole up close for long enough to prove it.
"I think he would have loved a Nobel prize and of course he cannot ever have one now because they don't award it posthumously," says Ms Hawking. "But what really matters is that the work lives on and inspires generations of students to engage in science in whatever way they can."
Ms Hawking chairs The Stephen Hawking Foundation, which promotes the understanding of cosmology, astrophysics and fundamental particle physics in schools and universities, as well as supporting work related to motor neurone disease. She also co-wrote a series of children's books with her father about science.
She is one of three children Hawking had with his first wife, writer Jane Wilde Hawking, to whom he was married for 30 years before they divorced in 1995.
It was poignant, she says, to work on the book and to glimpse herself in its pages, such as when he writes of achieving a breakthrough in his theory on black holes shortly after she was born. "It was just a silly family thing we used to do, to say happy birthday to me and happy birthday to the colliding black holes," she recalls. "It used to make me laugh."
His last words to her were that she had been a lovely daughter, and that she should be unafraid.
"He was an incredibly brave person," she says. "He understood that I have been quite a nervous person and he wanted to encourage me to have faith in myself."
When her father died, the family received a flood of tributes and Ms Hawking met many young people who use assistive technology to communicate, as her father did. "There was a little boy who had to use his toe to operate his machine and he told me that when he grows up, he wants to be like Stephen Hawking."
•Brief Answers To The Big Questions by Stephen Hawking ($22.34 before GST) is available from major bookstores.