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People thought about the stars long before we had telescopes. Greek scientists such as Aristotle (384–322 B.C.) and Ptolemy (A.D. 100–165) said that the Sun goes around Earth.
This seemed very clear to most people. Not many even questioned the idea. Then, in 1543, Polish astronomer Nicolaus Copernicus had a new idea. He said that Earth actually traveled around the Sun. For decades, people tried to say if he was right or wrong. The telescope became key to finding the answer. Telescopes have since become more high-tech. They have taken our knowledge beyond Copernicus’s dreams.
1609
◀ Italian scientist Galileo Galilei hears about the new Dutch instrument for seeing far. He builds one and uses it to look at the sky. He soon sees that Copernicus was right. For example, people who say Earth is the center of the universe argue that no other planet has a moon. This, they say, shows Earth is special. But with a telescope, Galileo finds four moons around Jupiter. Today we know it has many more! His findings help make telescopes popular in Europe. But he makes some religious people angry. In 1633, the Roman Catholic Church makes him take back his ideas about science.
1663
Scottish astronomer James Gregory (right) builds a reflecting telescope. It uses mirrors, not lenses. Five years later, Isaac Newton makes the design better. He creates the Newtonian telescope. ▶
1733
◀ English mathematician Chester Moor Hall makes refracting telescopes better. His design puts two different types of glass together. This keeps colors from separating. No more rainbow ring around images.
1781
William Herschel, an English astronomer, discovers the planet Uranus with his own telescope. He soon builds the world’s first giant reflector. Its mirror is 48 inches wide. His sister Caroline uses it to find eight comets. ▶
1814
◀ German lens maker Joseph von Fraunhofer sees something while looking through a telescope. He spots dark lines in the spectrum of visible light. Later, scientists find a use for these lines. The lines let us figure out the temperature of stars. They also help us find out what is in stars.
1835
German chemist Baron Justus von Liebig invents the modern mirror. It is a piece of glass with a thin silver coating. This makes building bigger reflecting telescopes possible. Before this, mirrors were shiny metal and very heavy. ▶
1845
◀ William Parsons, the Third Earl of Rosse, builds a reflecting telescope. Located at his estate in Ireland, it has a 72-inch mirror. It is the world’s biggest reflecting telescope. It holds that record until 1917. That’s when the 100-inch Hooker telescope is built near Los Angeles.
1889
George Ellery Hale invents the spectroheliograph. This instrument shows details of the Sun’s surface. He later builds some of the world’s biggest telescopes. One of them is the world’s largest refractor, the Hale Telescope on Palomar Mountain in California. ▶
1932
◀ Bell Labs engineer Karl Jansky is on a mission. He has to find out what’s making the noise that’s blocking radio signals. He discovers it is coming from space. Noise from space? Jansky has accidentally invented radio astronomy.
1957
The Soviet Union (now Russia) launches Sputnik. It’s the first human-made satellite. This leads to satellites and probes taking telescopes into space. In 1959, Russia’s Luna 3 first shows the far side of the Moon. ▶
1960s
◀ Scientists find new ways to detect infrared, ultraviolet, X-rays, and other invisible radiation. They give us new ways to study the universe. Shown here is Earth in ultraviolet.
1980s
If it’s wider than 15 feet, a mirror sags under its own weight. That bends images. Engineers find two ways to get around this. They can use a honeycomb base to support the mirror. Or they can put many small mirrors together to make one big mirror. ▶
1990s
◀ NASA launches the Hubble Space Telescope. It is one of the largest observatories in space. It is named after astronomer Edwin Hubble (left). Also launched is the Chandra X-Ray Observatory.
2000s
The Spitzer Space Telescope (right) is launched. It is used to see infrared light. The Swift telescope is also sent into orbit. Its job is to scan the skies for strange, superbright flashes known as gamma-ray bursts. They are the most powerful explosions in the universe. ▶
2010s
◀ The Hisaki ultraviolet telescope is launched. Its mission is to study the atmospheres of Venus, Mars, and Jupiter’s moon Io. The Giai observatory (left) is also put into orbit. It can map up to a billion stars in the Milky Way galaxy.
2020s
The James Webb Space Telescope is launched. It provides the deepest pictures of the universe ever seen. The sharpest, too. They include light from one galaxy that traveled 13.1 billion years before it was observed. ▶
