Part of the show The Science of Nanotechnology
Ernesto in Puerto Rico asked:
Down here in Puerto Rico we're supposed to have the largest radio telescope in the world. Is that true, and in fact how does a radio telescope actually work?
Yes that's absolutely true. The biggest radio telescope in the world is the Arecibo radio dish down in Puerto Rico. They essentially work in a similar way to a normal radio telescope but if you look at them, they don't look quite the same. They look just like a really big satellite dish. They work in pretty much the same way. The white surface that forms the big dish acts just like a mirror, and reflects radio waves up to a detector in the centre. That forms an image, focuses the radio waves and creates the radio image that we can look at galaxies with. It also has the added of advantage of allowing us to do radar pings in the same way that a speed camera would catch you in your car. We can actually ping radar off of Saturn or other planets to see how far they are away and also to calculate speeds. We can use the red shift or doppler shift of the radio waves to do this. If you fire a radio beam at Mercury, for example, you can actually see that light that's bounced off one side is altered as compared with light that's bounced off the other side because of the way the planet is spinning. In that way you can see how fast Mercury is spinning.