Ufo (Visiting the aliens)

A lot of people say that they have seen UFOs. Other people say they have been inside them. Not all of these stories are true; some of them are probably dreams, some stories of meetings with aliens sound true – although we can never be sure.

UFOs sell newspapers, and many newspapermen want to use UFOs in their stories. Because of this, some people have taken hoax photographs of UFOs to sell. Many scientists think that all UFOs are hoaxes. Certainly there have been some very clever hoaxes in the last fifty years.

It’s easy to make a photograph of a UFO. You need a small model of a spaceship. You photograph this one, and then take another photograph of the place where you want people to see the UFO. There are many photographs of UFOs taken by a man called George Adamski. Many people now believe that these are hoaxes.

There are also photographs of aliens. Many of these are probably hoaxes as well. Sometimes people see strange things in the sky, and they think that they are UFOs. When experts look carefully at them they sometimes discover that they are airplanes, balloons or even meteors.

Other photographs of UFOs look like flying sauces, but are probably just birds. Sometimes people have taken a photograph of a building or of something in the sky. When they look at the photograph later, they see a UFO. Often, this is a reflection of light in the lens of the camera. There are even photographs taken on the moon which show UFOs. These are probably just reflections, although some people think that they are aliens watching the spacemen.

Most experts think that most UFO stories are not real; but there are still a few stories which are very difficult to explain.

Hubble Space Telescope

Hubble Space Telescope is also called Space Telescope the most sophisticated optical observatory ever placed into orbit around the Earth. The Earth's atmosphere obscures ground-based astronomers' view of celestial objects by absorbing or distorting light rays from them. A telescope stationed in outer space is entirely above the atmosphere, however, and receives images of much greater brightness, clarity, and detail than do ground-based telescopes with comparable optics.

After the U.S. Congress had authorized its construction in 1977, the Hubble Space Telescope was built under the supervision of the National Aeronautics and Space Administration (NASA) of the United States and was named after Edwin Hubble, the foremost American astronomer of the 20th century. The HST was placed into orbit about 600 km (370 miles) above the Earth by the crew of the space shuttle Discovery on April 25, 1990 (see photograph).

The HST is a large reflecting telescope whose mirror optics gather light from celestial objects and direct it into two cameras and two spectrographs. The HST has a 2.4-metre (94-inch) primary mirror, a smaller secondary mirror, and various recording instruments that can detect visible, ultraviolet, and infrared light. The most important of these instruments, the wide-field planetary camera, can take either wide-field or high-resolution images of the planets and of galactic and extragalactic objects. This camera is designed to achieve image resolutions 10 times greater than that of even the largest Earth-based telescope. A faint-object camera can detect an object 50 times fainter than anything observable by any ground-based telescope; and a faint-object spectrograph gathers data on the object's chemical composition. A high-resolution spectrograph receives distant objects' ultraviolet light that cannot reach the Earth because of atmospheric absorption.

About one month after launch, it became apparent that the HST's large primary mirror had been ground to the wrong shape owing to faulty testing procedures by the mirror's manufacturer. The resulting optical defect, spherical aberration, caused the mirror to produce fuzzy rather than sharp images. The HST also developed problems with its gyroscopes and with its solar-power arrays. On Dec. 2–13, 1993, a mission of the NASA space shuttle Endeavour sought to correct the telescope's optical system and other problems. In five space walks the shuttle astronauts replaced the HST's wide-field planetary camera and installed a new device containing 10 tiny mirrors to correct the light paths from the primary mirror to the other three scientific instruments. The mission proved an unqualified success, and the HST soon began operating at its full potential, returning spectacular photographs of various cosmic phenomena.