![]() ![]() Light is one type of electromagnetic (EM) radiation, energy that is transmitted through space as a wave. Light can travel across empty space, and as it does, so it carries both energy and information. But for the most part, astronomers have one main source for their data - light. Very rarely matter from outside Earth’s environment reaches us, such as when a meteorite makes it through the atmosphere from elsewhere in the solar system. Astronomers observe their subjects at a distance, usually a very large distance! Electromagnetic RadiationĮarth is separated from the rest of the universe by very large expanses of space. But astronomers, scientists who study the universe beyond Earth, rarely have a chance for direct contact with their subject. Geologists can chip away at rocks to see what is inside. Physicists can subject metals to stress or smash atoms into each other. Biologists can collect cells, seeds, or sea urchins and put them in a controlled laboratory environment. Many scientists interact directly with what they are studying. Describe historical and modern observations made with telescopes.Identify different types of telescopes.Explain how astronomers use the whole electromagnetic spectrum to study the universe beyond Earth.The scientists won a Nobel Prize for their work in 1978. As the universe expanded, this high-energy radiation stretched into low-energy microwaves. It turned out that the pair had discovered the "afterglow" of the big bang - radiation emitted not long after the big bang, when the universe was very hot and dense. Initially, they suspected the source might be pigeon droppings, but the noise persisted even after they swept the antenna clean. It was later opened up for use by astronomers, and in 1965 Bell Labs' Arno Penzias and Robert Wilson discovered a constant "static" at microwave wavelengths no matter where they looked in the sky. Built in 1959, it was originally used to bounce radio waves off a simple satellite called Echo 1 and record their faint reflected signals. The Horn Antenna at Bell Telephone Laboratories in New Jersey was used to make one of the most important discoveries in all of astronomy - the detection of the cosmic microwave background radiation. (Image: Biller Miller, from Eyes on the Skies: 400 Years of Telescopic Discovery by Govert Schilling and Lars Lindberg Christensen) Today, computers take care of a telescope's slow tracking motion, which is needed to compensate for the motion of the sky due to the Earth's rotation. In this 1946 photo, the observatory's night assistant Gene Hancock smokes his pipe while manually controlling the motion of the 60-inch telescope. This "Coudé system" allowed astronomers to use many different instruments to analyse the light. The talented optician George Ritchey designed the 60-inch (1.5 m) telescope, pioneering a way to deflect light to instruments outside the telescope. The indefatigable George Ellery Hale eventually built this reflector on Mount Wilson, northeast of Los Angeles, California, in 1908. (Image: Science Photo Library: from Eyes on the Skies: 400 Years of Telescopic Discovery by Govert Schilling and Lars Lindberg Christensen)Įven as the colossal Yerkes refractor in Wisconsin was being dedicated in 1897, the glass for what would become the first of today's generation of telescopes - a large reflector - was sitting in the basement below it. In the years to come, Galileo's observations - including the discovery of four large moons orbiting Jupiter - would lend credence to the sun-centred worldview of Nicolaus Copernicus, who removed the Earth from its central position in the universe. Here you can see Galileo demonstrating one of his telescopes to the ruler of Venice in August 1609 (Galileo is standing to the right of the telescope). And he was the first to realise that it could be used to study the heavens rather than just to magnify objects on Earth. Though he didn't invent the telescope, Galileo improved on its design - gradually increasing its magnification power. Lipperhey found that placing a convex lens at one end of a tube and a concave lens at the other allowed him to magnify distant objects. The oldest existing documents attribute its invention to the Dutch spectacle maker Hans Lipperhey in the early 17 th century. The exact origin of the telescope is still controversial. ![]()
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