Yesterday we visited the Arecibo Observatory. This is the site of the world's largest radio telescope. A radio telescope is a lot like a regular telescope, except that it "looks" for radio waves instead of "looking" at light that we can see.

The radio telescope that we can see is like a giant antenna in the shape of a dish that is set into the ground. It is located where it is for several reasons. It was originally built by the United States Department of Defense to be used as military communications. It has been modified over the years to be used as a scientific tool. Since it was a military installation, it had to be in the United States, and Puerto Rico is a part of the US. They also wanted to use it to look at the planets in the Solar System and so it needed to be near the Equator where the planets are directly overhead. The mountain where it is built had a lot of the natural shape of the dome, so there would be less ground to dig up. The rocks that it is built on are very stable and strong so they could support the enormous structure. The valley that it is in protects it from stray radio signals and from wind because this area gets hurricanes sometimes.

A radio telescope is just like a large satellite dish that many people use to get TV. Instead up picking up satellites with television though it picks up radio frequencies from stars and other objects in the universe. It has helped discover many interesting things in space. One of the most interesting objects that has been discovered at Arecibo is the existence of planets that orbit stars outside of our own solar system. Though it is only a small part of astronomy, many people are interested in whether there is any other intelligent life in the universe. The scientists at Arecibo are among the people who may be able to answer that question one day.

Another important use of the radio telescope is to look at a part of our atmosphere called the ionosphere. That helps them understand more about how weather occurs on Earth. It also can look at the other planets and the asteroids in the solar system. These are objects much closer to home, the Earth, than stars and other galaxies.

The dish is just huge. It is 1000 feet across. It is perfectly in the shape of a section of a sphere. A ball is a sphere. Hanging over it in a very precise location is a triangular shape that holds the receivers. The information is fed to computers that are in buildings nearby. There the scientists gather and interpret the information that they get from the telescope. There is a visitor's center, dormitories for the scientists, lunchrooms, shops, maintenance , laundry facilities, and much more. It is a small city.

Many important scientific discoveries have been made at the Observatory, and new ones are being made all the time. Astronomers and Cosmologists run experiments on the radio telescope to help us learn about the nature of the universe and how it all began. These are questions that people have been asking since the first person looked up into the sky and wondered what the sun, moon, and stars were.