Telescopes are optical instruments that magnify a distant object and make it appear brighter.

Edwin Hubble used the Hooker Telescope to discover the universe is constantly expanding.

Early telescopes had two lenses at opposite ends of a tube.

Hans Lippershey invented the first telescope in 1608. It made objects look 3x their size.

Galileo improved on the design two years later. By making the objective lens less curved, magnification increased from 3x to 20x. He confirmed Earth goes around the Sun by observing that Venus has phases. Galileo's telescope had a very narrow field of view.

In 1688 Newton used mirrors instead of lenses and invented the reflecting telescope.

A telescope's power is the amount that it magnifies objects. If you double the diameter of the objective lens it gather 4x as much light. Triple, it is 9x. It is always the sqare of how much the lens is.

A degree is divided into 60 arcminutes and an archminute is 60 arcseconds. A 12cm diameter on the lens is equal to a 1 arcsecond resolution.

A satellite is an object that orbits a planet. The Hubble Telescope is a manmade satellite. Sputnik was the first manmade satellite launched in 1957 by the Soviet Union. NASA was created as a response in 1958.

Space Shuttles are at least partially usable satellites. Fourteen astronauts have been killed as a result of accidents on space shuttles.

Radar is a detection system that uses radio or microwaves to "see" objects. It has studied many satellites.

Rovers are vehicles designed to move across a planet or a moon.