Many people, when they hear the word telescope, think of some sort of tube you look through that has lenses or mirrors and lenses, that allows you to see a celestial object a lot closer. They would be partially right. The telescope I described might also allow you to see objects that were too dim to be seen with the naked eye. But this still is not a full answer since there are other types of telescopes that don't operate on light, they hear things such as radio energy coming from heavenly bodies. This is not to imply that there are people or beings using radio sets. What is happening is that most bodies put out some sort of electronic signature and the big disk can read it. It also is a huge radar set. By big dish I am talking about the 1000 foot diameter radio telescope at Arecibo in Puerto Rico. It can also detect other things like gas.

Arecibo Radio Telescope
Picture Source: NASA

When you see a picture made from a radio telescope it doesn't always look like a picture taken through a conventional telescope. You may not even be able to recognize the object the picture is of, but the astronomers do and they learn valuable data from these pictures. Here are a couple of pictures taken with the Arecibo telescope:

Notice how the craters on Mercury contrast with the rest of the planet. The moon doesn't look that much different to the untrained eye. Since Venus is covered in clouds, we get a better view here.

In 1974 a message was transmitted from the Arecibo telescope. It was aimed at the globular star cluster M13 which is about 25,000 light years away. The signal was transmitted on a frequency of 2389 MHz and the telescope had been modified to be able to broadcast up to a power of 20 terawatts. A Terawatt is 1 trillion watts. The signal was transmitted in binary numbers and formed a picture showing a representation of a human, the radio telescope, dna and some other items. Now here is the eerie part of the story. In Chilbolton in the UK a crop formation was reported on Tuesday, 21 August 2001. It was of a human face and a copy of the Arecibo message sent in 1974. The crop formation was near a radio telescope in the area.

SETI or the Search for Extraterrestrial Intelligence, has been around for 44 years now and has been involved, off and on, with the Arecibo telescope. Now SETI is planning on building their own radio telescope.

The Arecibo telescope is used for many things not only planetary or deep space objects. It can also track asteroids since it is also the world's most powerful radar system. A news release from May 4, 2000 show how the scope was used to track 216 Kleopatra, an asteroid that was between Mars and Jupiter. The asteroid's existence was already known but its shape was not. The asteroid is roughly the size of New Jersey. It came as a surprise when the pictures taken by the telescope showed the asteroid's shape was that of a dog bone.

216 Kleopatra Asteroid a series of shots.
Picture Source: NASA

William E. Gordon was the person that pushed for the construction of the Arecibo Telescope. He was a Cornell Professor of Engineering in 1958. He wanted to build an instrument that would use radar to study the ionosphere and solar system objects. He supervised the construction of the big dish. Since its construction it has been used for a lot more than it was designed for. Thanks to this telescope the first binary pulsar was discovered. The scope also discovered that there was ice on Mercury. New types and variations of radio telescopes are being used today and some are in large arrays that allow them to magnify signals in such a way to belittle their size, but Arecibo is still the king.