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**APRIL21**

* Soviet Progress 29 space freighter was launched and sent to dock with the Mir-Kvant-Soyuz TM-2 space station assemblage. The combined assemblage was 115 ft. long and had a mass of 50 metric tons (1987).

* Soviets fail in an attempt to dock with Salyut 7/Cosmos 1443 space station (1983).

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* Earth gets its own holiday; "Earth Day" delared (1972).

To understand how man is affecting Earth's environment, the Landsat satellite takes images (pictures) of Earth in different spectral wavelengths. In this way we can study what can be done to make Earth's future "Earth Days" happy ones for Earth.

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* Gus Grissom born (1926).

* Soviets perform a 4 hr, 15 min EVA in order to start repair of space station Salyut 7's engine system. The EVA is from a tether (1984).

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* Soviet cosmonaut Vladimir Komarov was first to die on a manned space mission when Soyuz descent para- chute entangles at 25,000 ft and craft drops to ground (1967). ("Guiness... Records," Furniss, p. 36)

* China's first satellite launches (1970).

* Hubble Space Telescope launched into low Earth orbit (1990). Click here for more about the Hubble Space Telescope.

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* Unmanned Mercury explodes on launch pad during test (1961).

* Hubble Space Telescope is deployed from the Space Shuttle (1990).

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* Soviets launched first geosynchron- ous satellite for study of atmosphere and oceans. It was called Cosmos 1970 and was launched by a Proton rocket (1988).

Note: A satellite in a circular geosyn- chronous orbit 22,300 miles above Earth has a fixed-view (w.r.t. to the ground) of 30% of the Earth's surface.

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* Apollo 16 splashed down in the Pacific Ocean (1972).

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* Newton published "Principia." Newton's colleague, Sir Edmond Halley, paid for its publication. The book explained the law of gravitation and created the science of astronomy (1686).

(Click on "Newton" button above for a biographical sketch of Newton.)

(The following information is paraphrased from "The Illustrated Encyclopedia of Astronomy and Space," Ian Ridpath, Thomas Y. Crowell, Publishers, New York, 1979, p. 142.)

** Sir Isaac Newton**

(1642-1727)

Isaace Newton is known as a British mathematical physicist whose discoveries included the idea of universal gravitation and important understandings in the field of optics. As a result of the Great Plague of 1665, Newton left Cambridge University to live in his home in Woolsthorpe, Lincolnshire, England. There, his research began and was continued on his return to the University after the threat of the plague had ceased. This work was summarized in his famous book, "Philosophiae Naturalis Principia Mathematica" (Mathematical Principles of Natural Philosophy), which is often called "Principia."

The crowning glory of Newton's work was the statement of understanding of the physical Universe in mathematical terms. This contribution combined the works of both Kepler and Galileo in a mathematical set of equations. Newton's work included the three famous laws of motion which comprise the laws of movement, momentum, and reaction of Earth's physical bodies. Furthermore, his understanding of the law of gravitation was stated as a mathematical formula which related gravitation attraction to the mass of two bodies and the distance between them. He found that the relationship was inversely proportional to the square of the distance separating two bodies.

In the field of mathematics, Newton founded Calculus in order to obtain proof of his results. Later use of Calculus proved very beneficial to science and technology. Newton's contributions to astronomy were numerous and innovative. He experimented with the dispersion of white light showing that white light was composed of a spectrum of every color of light. His work with light led to the design of a reflecting telescope which used mirrors not lenses. He constructed a mirror telescope in 1668, an item which has been one of the most important instruments of astronomy. His findings became the science of spectroscopy, which was the seed that grew into astrophysics, the study of the stars.

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* Spacelab 3 is launched aboard the Space Shuttle. Spacelab was produced by the eleven countries of the European Space Agency (ESA). The Spacelab conducts experiments in astronomy, solar-space physics, materials sciences, biology and atmospheric-Earth observation (1983).

* Construction of the "Spirit of St. Louis completed (1927).

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* Brightest supernova in recorded history seen in the constellation Lupus (1006). A supernova is an exploding star giving off a million times more energy than a nova explosion.

MAY 1

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