People doing shift work or those who have arrived after a long-haul flight have experienced the disrupted sleep and hunger patterns of a body clock which is out of tune with the rising and setting of the sun.
I must admit, this has never troubled me. In my past travels, when I arrived in a new time-zone, I adjusted straight away. The trip from England to Australia is one of the longest hauls. Once, I travelled for over 24 hours, stopping off at Abu Dhabi if I remember rightly. When I arrived in Melbourne, my brother-in-law drove me to Sandringham along the coast to see my father. I'd read somewhere that if you wade in the sea after a long flight, the effects are reduced. My father indulged me. Of course, it worked.
The body clock uses light to help keep track of time, but it is naturally stubborn and adjusts slowly.
The scientists used mice in their experiments. They found that interfering with the vasopressin receptors, essentially a brain cell's ears that allow it to keep in touch with its neighbors, let the clock shift rapidly. Read how they scientists constructed their experiments here. http://www.bbc.co.uk/news/health-24387491
My husband has a problem with sleeping. He can't fall asleep until about 4am and then wakes at around midday. This stems from working at night in his early years. Even before that, he would stay awake as a child to wait for his father to arrive home. Then, he could expect his father to take him to pubs and clubs in London, where his father would play the piano. These were the most exciting times of his life. But that was seventy years ago and times have changed rapidly since then.
A renowned writer has predicted the future one hundred years from now. Watch the fascinating three minute video here. http://www.bbc.co.uk/news/magazine-24331106
Essentially, James Burke predicts a very different life in the year 2100, in which the proliferation of 3D nanofabricators mean poverty and scarcity have become things of the past. There is no reason why we can't construct anything we want by using water, soil and air. There will be no more pollution because we won't need to cut down trees or dredge the soil. We can live where we choose and produce whatever background we like—the Eiffel Tower, the Wailing Wall, or the ever changing sea.
Maybe imagination and nanofabricators are one and the same thing. Just imagine a life without worry. That's my idea of Heaven on Earth.