Yes the signals we create are creating a sort of bubble around the earth which is expanding at the speed of light. That means that the bubble is roughly 100 light years across now and spreading away from the earth. But when you think that the Milky Way is easily about 100 000 light years across, it's going to take a long while for many of the stars just in our own galaxy to hear us. When you consider that there are 10 000 000 000 000 000 000 000 stars out there, it is going to take a long while before the messages get to anyone else. So it is not surprising we haven't heard anyone replying yet.

When your light switch is just on the border of making a circuit, you are creating a switch which is almost closed. At some point the switch will create a spark. When you create a spark you will create a little surge of current in the wire. The spark will then finish and break the circuit again. You will keep getting sparks, each creating it's own surge of current. Your light bulb is flickering because you have a changing current, and a changing current will produce a changing magnetic field. A changing magnetic field produces a changing electric current. So when we create a radio wave, what you've got is a transmitter which is applying a changing electric field to a piece of metal (the aerial). The changing current going up and down that piece of metal then induces a changing magnetic field around the metal and the changing magnetic field then creates a change in electrical current in the fabric of space around it. That electrical current in space time produce a wiggle of magnetic field, and so you get this wave that propagates as an alternating magnetic field and electrical field. This propagates through space at roughly the speed of light. That's a radio wave. So why did your interfere with your radio? Well when you're just on the verge of completing a circuit with your light, it's creating enormous amounts of changing current in the wire. This creates lots of funny frequencies of radio waves at a fairly low power. These then come out around the wire, spread out into the room and are picked up by the aerial of your radio. They interfere destructively. In other words they cancel out the radio waves of the station you were listening to. That's why you get the interference.

Animals are the colour they are to blend in with their environment. The key thing that drives survival is not being preyed upon or eaten. If you're not eaten then you get to have babies and you pass your genes on to the next generation. If you're a polar bear and your genes make you white, then you're less likely to be caught and eaten. As a result, you're more likely to have babies and those babies will have babies. So animals will change their colour so that they're the same as the surroundings and blend in. That either makes their hunting easier or they don't get eaten by other things. It might be that the colours you're referring to have not been adopted because they're not very good colours in nature. A snake is a greeny-brown colour because it wants to blend into the background. Other animals use the converse. They don't want to blend in because they want to mark out that they're toxic. That's why they use colour. The other reason they use colour, especially in things like fish, is for part of the mating game. It can be used for recognition and communication. Actually, I think baboons have big blue noses and I think there is a mammal that is green, although it's for a slightly different reason. It's called a three-toed sloth. The reason it's green is because moss grows on its fur as it moves so slowly.

I don't think so. The number of cases of this new form of CJD rose to a peak of 28 cases in the year 2000. Last year there were five. It looks very much that far from being a time bomb, numbers are dropping and the disease is under control. That's what I would say. When the first cases appeared in the end of 1995 and the beginning of 1996, nobody knew what the incubation period was. We knew that the maximum exposure of people to contaminated beef was around 1990 and so some people said that if there's a 20 year incubation period, then these first cases in 1996 might expand to hundreds of thousands of cases in 20 years time. Nobody could be sure that that wasn't right. It turned out that the incubation period is about ten years, BSE transmits very inefficiently to people and the maximum of 28 people in 2000 was the maximum. Now it's going steadily down.