The Planets series has finished. But in case viewers have not had enough of space, the story is taken further by a documentary posing the biggest question of all: what fate awaits not just our planet, but the universe? From Here To Infinity (Pearl, 8.30pm) explores the latest findings by rival teams of supernova hunters that could force physicists to reassess their understanding of the universe and review the fundamental laws of physics.
Until now, we have not known whether the universe would expand to infinity or contract in a cosmic crunch. The findings in this programme, presented in Britain last year, were hailed by science journals as the scientific breakthrough of the year. It claims to have the answer.
An international team headed by Saul Perlmutter perfected a technique for tracking rare and distant supernovas, enabling astronomers to view exploding stars.
What they saw suggests galaxies are accelerating away from each other, and that the universe is speeding into infinity. Instead of gravity slowing the universe, as previously thought, an unknown energy could be pushing against gravity, flinging the universe apart.
The implications of this are hard even for astronomers to prove and grasp. But Perlmutter helps out by describing what our night skies could look like in billions of years time. Instead of the myriad galaxies lighting up the skies, all we would see would be black emptiness. A time could come when the last star could be put out.
Another wondrous mystery much closer to home is pondered in Mystique Of The Pearl (World, 10pm). For centuries, humans wondered how one of nature's most lowly creatures, the oyster, could produce one of the most beautiful and perfect of nature's creations, the pearl.
Today's aquaculture techniques are a far cry from the earliest hunting for pearls. In the underwater farms of Japan and Australia, oysters are caged and tended like prize breeding herds. The secret of how an oyster is 'nucleated' and encouraged to grow a perfectly round pearl is revealed.
From there, the programme follows the less interesting progress of the pearl from auction rooms and jewellery workshops to fashion houses, ready to decorate the world's wealthiest women.
Earthly challenges are the subject of what is billed as the most dangerous show on TV, though no serious accidents have been reported as yet.
In the first show of the new season of Don't Try This At Home (World, 9pm) an arachnophobic housewife confronts her worst nightmare, by standing in a booth full of spiders. Meanwhile, two members of the audience are challenged to dive 160 kilometres an hour through the air. This week's challenge of a lifetime is accepted by a disabled man, who is taken to the highest cable car in the Alps where he is to leave his wheelchair and abseil 300 metres to the ground.