Science and technology

Hester Quayle: Good evening, everyone. I lead the engineering team at Carrow Moor Observatory, which, if you've ever driven along the moor road, is the one with the enormous white dish that looks as though it's listening to something. It is. It's listening to radio waves that set off from distant galaxies long before there was anyone on Earth to receive them. Hester Quayle: I'm often asked how I ended up doing this, and people tend to assume I was one of those children who spent every clear night peering through a telescope. My grandfather did own a rather fine one, and he once took me to a planetarium for my birthday, which I mainly remember for the ice cream. But what really started it was a crystal radio kit my aunt gave me when I was nine. No batteries, just a coil of wire and an earpiece, and late at night I could pick up voices from other countries. The idea that invisible signals were passing through my bedroom the whole time never quite left me. Hester Quayle: The signals we study now are so faint that an ordinary phone switched on in our car park could drown them out entirely. That makes visitors something of a headache. When we first opened for tours, we simply asked people to switch their phones off, and a surprising number either didn't or thought they had. Then we installed wooden lockers by the entrance, which looked very smart but, as it turned out, did nothing whatsoever to stop the signals getting out. So these days every phone goes into a metal cabinet in the visitor centre, and it stays locked until the tour is over. People grumble, but I suspect most of them are secretly relieved to have an hour without it. Hester Quayle: The story I really want to tell you tonight, though, is about the winter we thought we might have stumbled on something extraordinary. For about three months, the dish kept picking up short, sharp bursts of radio energy. They weren't regular, which ruled out anything like a spinning star, but they kept on coming. Our first theory was a newly launched satellite, but when we checked, the bursts didn't match any orbit. Next we suspected our own equipment, specifically the cooling system on the receiver, and we spent a miserable fortnight taking it apart, only to find nothing wrong with it at all. Hester Quayle: What cracked it in the end was the timing. The bursts only ever arrived late in the evening, and only on the coldest nights. One of our younger engineers drove round the lanes with a portable antenna and followed the signal to a farmhouse about two kilometres away, where an elderly gentleman had been sleeping under an electric blanket with a faulty thermostat. Every time it clicked on and off, it was broadcasting straight into our dish. We bought him a new blanket, and the bursts stopped that very night. Hester Quayle: I tell that story because it's funny, but also because it makes a serious point. The same technology that allows us to hear the universe is also filling the sky with noise, and the thousands of satellites now being launched are a far bigger problem than one old blanket. Discovery has always depended on instruments. What worries me is that we're making the silence those instruments need harder and harder to find.