Most people would find life as a professional physicist a full-time job. But for Russell Stannard that was just the starting point for a career that would make him a renowned children's author and popular religious commentator.
Professor Stannard still has vivid memories of the moment it all began - when he was told about Einstein's theory of relativity in the early 1950s.
As a physics undergraduate at University College, London, the revelation that time slows down, and things get heavier as they approach the speed of light astonished him.
"It was absolutely wonderful, amazing science," he said. "But I was angry that no one had told me about this before. It seemed a scandal that Einstein's theories had been around for so long but were not part of everyday culture.
"Our first introduction to the mind-blowing world of modern physics should be when we are young, when our minds are still open and flexible. As we get older, we become set in our thinking, our view of the world fossilises; we become resistant to new modes of thought."
But thanks to Professor Stannard, now a white-haired 67-year-old who recently retired from the Open University, thousands of children do not have to wait so long.
They have been introduced to the complex ideas of relativity and quantum physics by Uncle Albert, a wild-haired elderly gentleman who can conjure up spacecraft using the power of thought and send his niece on spectacular adventures through time and space.
Like Albert Einstein, Uncle Albert - Professor Stannard's most famous creation - doesn't wear socks, plays the violin and likes sailing.
Einstein made his discoveries not in a lab but by using the power of thought. He would visualise an everyday situation and then mentally push it to extremes. These became known as his Gedanken, or thought experiments, which is the name Professor Stannard chose for his heroine in the Uncle Albert books.
But it was decades before Professor Stannard realised his dream.
"In academia you do not get brownie points for popularising science. I just led an ordinary scientist's life, you churn out academic papers and eventually you become a professor. Only then can you really begin to let your hair down."
So it was nearly 40 years later, after a distinguished career as a physicist, OU professor and pioneer of open learning, that Professor Stannard embarked on his quest to explain relativity to children.
His "Eureka" moment came when his wife was studying for a BEd and came across a child psychologist Jerome Bruner who said that you could teach any subject to any child, it was just a case of finding a "courteous translation".
He said: "So many adults dismiss relativity because it seems to go against common sense. But we should be careful. Einstein himself once defined common sense as "that layer of prejudice laid down in the mind before the age of 18".
But he began his book more like a scientist than an author. He read up on child psychology and spent hours analysing the date stamps in children's books in his local library to see which were borrowed the most and then tried to imitate what made those books so popular.
Unsurprisingly he found that short chapters, lots of conversation, good illustrations and a young hero or heroine that children could identify with were vital.
He wanted to aim the book at the youngest possible audience, finally settling on 11-year-olds because he felt younger readers would have difficulty understanding concepts such as the difference between speed and acceleration.
He also took children's cognitive development into account. "Most children are concrete thinkers - they think outward from experience and can't take on board theoretical abstract models.
"So in my book I started with the consequences as if they are being experienced by my heroine and wrap them up in an entertaining story with all the science at the end for the people who can cope with it. Many adults think this way too. However, many professional scientists do not recognise that people think differently, which is why I think many attempts to popularise modern physics fail."
Publishing the book, however, was a different story. Educational publishers wouldn't touch it because it wasn't a textbook while children's publishers said "it's great story but what's all this science?".
He said: "It was getting very dispiriting getting all these rejection letters. Then I heard that William Golding had Lord of the Flies rejected 17 times. I decided that if the Nobel Prize winner for literature was prepared to send off a manuscript 18 times, I should do the same."
The 18th publisher he tried was Faber, the eventual publisher of Lord of the Flies. They accepted it and it was an instant success, selling out in three weeks.
Since Uncle Albert's debut in 1989, Professor Stannard has published six books featuring the eccentric scientist plus many more explaining both science and religion for children. Last year he was awarded an OBE for his services to physics, the popularisation of science and the OU.
Uncle Albert was not Professor Stannard's first departure from the traditional career path of the professional physicist. In the early Eighties his papers on particle physics gave way to books, articles and radio programmes on theology and the links between science and religion.
He is a deeply religious man and has been a Reader, or lay preacher, in the Church of England for more than 30 years. He came to the Church late, his family was not religious and it was through reading the lessons at his school's services that he found his faith.
He said: "I just felt completely at home there. Some people find churches alien places to be but being there had a big effect on me. It has been a journey of experience since then."
Nothing in his science has ever caused him to question his faith, but other people found it an unusual combination and he began to be asked to explain his views on science and religion. This led to lectures and a book on science and belief and today he is a regular contributor on Radio 4's "Thought For the Day".
He said: "People grow up with terrible misconceptions about science and religion. They just see them in terms of conflict. Science is not the answer to every question. Science can tell you how but it does not get involved in why."
He sounds almost angry when he mentions scientists such as Peter Atkins, of Oxford University, and Richard Dawkins who say science is incompatible with religion. He said: "The things they say are so attention grabbing and outrageous that they get into the papers and it becomes very difficult to nail those misconceptions."
He is also a keen sculptor. Inspired by Henry Moore, much of his spare time is spent in his Bedfordshire garden, where he constructs towering shapes out of polystyrene covered in car bodywork filler.
And there are many more books in the pipeline. His latest, Space, Time, Rhythm and Rhyme, published last month, introduces children to astronomy and cosmology using a punchy narrative alongside poems selected by Professor Stannard.
"I try to get into the mind of the child in my books", he said. "I've got 12 grandchildren and go into local schools a lot. I've always felt there was part of me that has never grown up."