Stephen Hawking's Universe (BBC2) began last week with the big questions: "Where do we come from?" "How did the universe begin?" The programme itself raises rather smaller ones - most pressingly "How do you fit the universe onto a television screen?" As the first episode had pointed out, the story of how we arrived at our current picture of the universe is the story of "learning to understand what we see". But a mental picture is very different from a real one - and the translation between the two presents the series with something of a recurring problem. Philip Martin, the director, has a fondness for blurring and distortion - which makes sense if you are reconstructing a meeting of famous physicists and don't want viewers to be distracted by a duff Einstein, but which can be unhelpful when the viewer is struggling to get chaos into some kind of manageable shape.

The opening programme offered a brief history of cosmological perception - from the Greek notion of a divine fire shining through the holes of the stars to Edwin Hubble's discovery that the universe was expanding in all directions. It was, too, a history of the long grudge-match between science and religion, a fixture which still continues despite professional fouls from the ecclesiastical team, such as Galileo's enforced recantation. Last night's episode ameliorated the sense of head-on confrontation - acknowledging the involvement of a Belgian abbe called George Lemaitre in the development of the Big Bang theory. But it didn't blow the final whistle on the game - ending with Hawking's reminder that the Pope had warned cosmologists that it would be irreverent to inquire into the nature of the Big Bang itself. You can play, but no kicking the ball down our end.

All of this is difficult to explain and even harder to show. Many of the images try rather too hard, in my view, not to be diagrammatic, offering a trippy, impressionistic rendering of cosmic mysteries rather than focused images of the real thing - decoration instead of illustration. While these sequences have a certain nebulous beauty (appropriately enough) they amplify rather than diminish your confusion. The graphics were credited to Tomato - which I take to be a design company - though more than once it looked as if they'd just hurled the fruit in question at the camera lens. Even so, it is engrossing stuff, quite capable of arousing an existential shudder at the terror of those infinite spaces.

Full Circle with Michael Palin (BBC1) has a much easier task - either point the camera at the presenter (who is engagingly prepared to prat about in remote places) or point it at the scenery - which in this first episode (repeated after being dislodged on to BBC2 by last week's news coverage) was both unfamiliar and dramatic. Palin started his journey round the Pacific Rim in Little Diomede, a collection of large packing cases on a rock in the Bering Strait - "In a year's time," he said "if all goes well, we shall have gone full circle." And if all doesn't go well, you thought, the producer will pull out his gold Amex and charter a plane. Fortunately, Palin knows that the audience will no longer buy the illusion of solitary adventure. "What more could I ask for," he said as he left Little Diomede in a walrus-skin boat, "except a helicopter, like the rest of the crew?"

He soon got one, and probably regretted the wish - being obliged to fly down the remote Kamchatka Peninsula in a fearsomely rusty Soviet chopper. He was now travelling with Igor, a man with a baldie comb-over almost as spectacular as the surrounding volcanoes. Palin didn't allude to it, but elsewhere the series depends on his refusal to ignore the less attractive aspects of the journey: "We're in luck - somewhere beyond the flies is a bear," he noted drily, during an insect-challenged excursion in Alaska. Quite often, the pictures join him in this gentle sardonicism - "From here there's only one quick way out," said Palin about Nome, Alaska. He meant the airport, but you couldn't help noticing that they'd framed the relevant shot over the local cemetery.