Last Night's TV: He treated this with just the right gravity

Horizon, BBC2; True Stories, More4; Medicine Men Go Wild, Channel 4

Gravity, explained Dr Brian Cox in Horizon, not only gets the credit for the fruitful lumpiness of the cosmos, without which life wouldn't exist at all, but it has also spawned some of "the most abusive slanging matches in modern science". This rather had the feel of a promise to me. Stick around, it said, and you'll get to see men in white coats kicking chunks out of one another over the fundamentals of physics. Which made it slightly odd that the film that followed should be such a decorous and genial affair, with not a cross word to be heard. Not many intelligible words either, to be honest, though it wasn't for want of trying on Cox's part. In a refreshing sequence in the middle of the film, there was a kind of out-takes montage, which showed him grappling helplessly for a way to explain the deformations of Einsteinian space-time, a rare acknowledgement from a science documentary that simplification can be a tricky business.

Cox once played keyboards for D:Ream, his last public appearance in that capacity being on election night in 1997. In an act of heroic self-restraint, Horizon chose not to mention this fact, quite something given the reflexive grasping after any kind of value-added celebrity that is now commonplace in BBC documentaries. Instead, they just let him take a road trip around the United States, visiting observatories and labs that would help liven up his beginner's guide to gravity. In El Paso, he talked to a man who aims lasers at a tea-tray-sized target on the moon in order to work out its exact orbit. Apparently, Isaac Newton, the duffer, was 10 metres out in some of his calculations, which isn't a problem at all if you're planning to drive to the moon but is more critical if you want to work out exactly how gravity keeps it where it is.

In Colorado, Cox popped in on the US Air Force personnel who maintain the global positioning system, men who have to cope with some of the worst haircuts on earth and the fact that Einstein was right and clocks run faster in weaker gravity, and in Louisiana, he visited the Laser Interferometer Gravitational-Wave Observatory, the largest precision optical instrument in the world. This hugely expensive installation has been working steadily for five years now without a single successful sighting of a gravitational wave, which made you wonder how exactly they can be sure that it doesn't fall into the same category as a Bigfoot Inspection Tower or a Mermaid Sonar Array. Things got even more nebulous when Cox talked to another scientist about the fruitless search for gravitational particles. He explained that he believed they were so elusive because they kept disappearing into another dimension, which sounds like the kind of theoretical get-out clause that could have many real-world uses. Anyway, we weren't much the wiser by the end, except to understand a bit better how limited our collective wisdom still is. Which isn't the worst outcome a science programme can have.

Who Am I? The Found Children of Argentina, shown in the True Stories slot, also concerned disappearances, though these had been engineered by the military during Argentina's Dirty War. The children and babies of those murdered by the military junta were often abducted and handed over to new parents as part of the process of eradicating the enemies of the state. This film was about the children who were eventually retraced, due to the efforts of the Grandmothers of the Plaza de Mayo, and it understandably presented the campaign as a triumph of love over cruelty and deceit: "Most of the children we found were living a huge lie," said one formidable old lady. Except, of course, they often didn't know it until they were told. All those who took part here were happy, in different degrees, to have had the truth finally emerge even when they learnt appalling things about the fate of their biological parents. But, as moving as the stories were and as satisfying as it was to see former torturers and murderers brought to justice, you wondered whether it was the whole story. There must have been children who were shattered to discover the truth about their origins, never able to recover their true parents or again feel the same way about their false ones. For them, a torture had been inherited.

Chris and Xand van Tulleken engaged in self-torture in the second episode of the engaging Medicine Men Go Wild, pushing skewers through their cheeks and tongues as they experienced a Hindu ritual in Kuala Lumpur. They discovered that it hurts like hell, but also, thanks to a group called the Federation of Indian Rationalists, that divine trances or purification rituals are not really necessary if you want to impale yourself on hooks and smile while doing it. Even Xand managed it, after going a bit whey-faced for a while. The secret, as Lawrence of Arabia said in the film, is not to mind.