IT SOUNDS like the punchline to a joke about nerds going on holiday: maths tourists travel thousands of miles in search of - nothing. But that is the draw of Gwalior, in India, where you are invited to admire the first known transcription of the mathematical term zero, or 0.

Dating back to 875, this insubstantial figure speaks of the sophistication of Indian philosophy, mathematics, and theology in an era when most were still trying to make use of a clumsy and prolix Roman system of numbers.

All this and much more was explained in Nirvana by Numbers (Radio 4, Monday of last week), a one-off documentary presented by Alex Bellos that did an admirably efficient job of explaining why the East had it sussed well before Western European thinkers. In fact, the number-place system that we now all use - and which necessitates the use of zero - appears to have originated several centuries before that first recorded example, and arises from a culture where the ritualistic use of number was a theological necessity.

In the Vedic period of India's history, mathematicians had already calculated an approximate value for Π; conceptualised the square root of two; and figured out Pythagoras's theorem (before Pythagoras).

The ambition that lay behind all these calculations came from an intrinsic association between number symbols, and names for physical and cosmological phenomena. Thus, an expression of pi to the 20th decimal place can be both a string of numbers and a poem.

It sounds like something that Between the Ears (Radio 3, Saturdays) might be interested in, but in a treatment laced with radiophonic trickery and esoteric exposition. Between the Ears has been a hit-and-miss affair, but one can only delight in the fact that there is still a slot in the schedules for radio experiments such as Shadowplay, the "radio symphony in four movements", which is being broadcast this month to mark the 20th anniversary of this strand.

Last week, we heard the internal monologue of a film producer whose yogic meditations are interrupted by the appearance of the film star Harvey Keitel. He enters into imaginary dialogues with Keitel through the actor's best-known films, such as Pulp Fiction and The Last Temptation of Christ.

The whole meditation was underlaid with the sound of deep breathing, and I wondered whether it ought not to have been introduced by a warning not to operate heavy machinery while listening, so soporific was the effect. And yet it remains the most memorable radio experience of the week, and one that speaks to the importance of Between the Ears as a radio institution.

Twenty years ago, the importance of the internet as a means of redefining our political and personal relationship was only just entering our consciousness. In Digital Human (Radio 4, Monday of last week) we heard about its power to facilitate altruism. It was comforting to hear about schemes such as the one on the website randomactsofpizza.com, on which you can buy pizza for a stranger in need while munching on your own in front of the computer at home.