I knew it! OK, I know I start a lot of blog posts like that, but this time I almost, practically did know it.

When I was a teenager, and dinosaurs stalked the land, I used to lay on my front, on the living room carpet, a foot or two from the TV screen and watch Horizon, especially loving programmes devoted to quarks, black holes, the big bang or the nature of the fundamental forces. I didn't understand all (or probably much) of it, but I got just enough sense out of the explanations (and Radiophonic sound cues) to realise it was all extremely cool.

Now, after lo these many years, I know a lot more science, and I've sometimes wondered whether that's the reason modern Horizon programmes seem to me as though they're pitched at dizzy labradors rather than science fans. Perhaps they're telling me things I already know. But that doesn't really explain it. These days there's vanishingly little science content, only human interest stories and abstract visuals - which though pretty, tend to over-punctuate every programme, giving you six seconds between each utterance so that you can meticulously process the boilerplate hyperbole, e.g. "But what was to come next was to turn those ideas upside down. It was a revelation that no one could possibly have foreseen." Yawn. I get very tired of being given five minutes build-up to each pre-digested fact. And my suspicions about the good old days were finally confirmed when I watched Lost Horizons: The Big Bang at the weekend. It was a sort of clip show of Horizon instalments mainly from the Seventies and Eighties. And there they were, sequences of facts delivered one upon the other in a brisk but unhurried sequence. We weren't told how to feel about each one before it arrived. We didn't have to endure a mixed metaphor or even a stale cliche about how 'things would never be the same again'. Those old programs attempted to convey complex science to an intelligent audience of scientific amateurs. I knew there was a reason I used to watch it.

Now I will give modern Horizon this: it does some wonderful things with out-of-focus images of cityscapes or headlights on highways, and its mood music is often excellent; but in terms of contaminating its chilled-out bombastics with any educational content, it's become a sort of scientific muzak. Ideally I would like it to return to its original mission and stop thinking we're afraid to learn anything, but I don't suppose that's going to happen.

But at least their recent retrospective enabled me to identify the problem. You'll all be relieved to know that I haven't got incomparably smarter since I was a teenager; it's just that the BBC has decided we're all morons.