Some great scientists of the world
Newton
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Isaac Newton (1642-1722) was the British scientist who first explained how gravity works. Newton’s ideas were inspired by seeing an apple fall from a tree in the garden of his home in Lincolnshire. Newton also discovered that sunlight can be split into a spectrum made of all the colours of the rainbow. A If ordinary white light is passed through a glass prism, it splits up into all the different colours of the light spectrum.
Newton showed why gravity makes things fall to the ground and planets orbit the Sun. Newton realized that a planet’s orbit depends on its mass and its distance from the Sun. The further apart and the lighter two objects are, the weaker is the pull of gravity between them.
Newton worked out that you can calculate the pull of gravity between two objects by multiplying their mass by the square of the distance between them. This calculation allows astronomers to predict precisely the movement of every planet, star and galaxy in the Universe.
Using Newton’s formula for gravity, astronomers have detected previously unknown stars and planets, including Neptune and Pluto, from the effect of their gravity on other space objects. Newton’s three laws of motion showed that every single movement in the Universe can be calculated mechanically.
Newton’s theory of gravity showed for the first time why the Moon stays in its orbit around the Earth, and how the gravitational pull between the Earth and the Moon could be worked out mathematically. Newton was made Lucasian professor of mathematics at Cambridge University in 1669, where he studied how and why things in our Universe move.
Kepler Johannes
Kepler (1571-1630) was the German astronomer who discovered the basic rules about the way the planets move. Kepler got his ideas from studying Mars’ movement. Before Kepler’s discoveries, people thought that the planets moved in circles. Despite almost losing his eyesight and the use of his hands through smallpox at the age of three, Johannes Kepler became an assistant to the great Danish astronomer Tycho Brahe, and took over his work when Brahe died. Kepler discovered that the true shape of the planets’ orbits is elliptical (oval). |
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This is Kepler’s first law.Kepler’s second law is that the speed of a planet through space varies with its distance from the Sun.A planet moves fastest when its orbit brings it nearest to the Sun (called its perihelion).
It moves slowest when it is furthest from the Sun (called its aphelion). Kepler’s third law is that a planet’s period - the time it takes to complete its yearly orbit of the Sun - depends on its distance from the Sun. Kepler’s third law states that the square of a planet’s period is proportional to the cube of its average distance from the Sun.
Kepler believed that the planets made harmonious music as they moved - The music of the spheres’. Kepler also wrote a book about measuring how much wine there was in wine casks, which proved to be important for the mathematics of calculus. A Johannes Kepler was sponsored in his research by Emperor Rudolph II. Here they discuss Kepler’s discoveries of planetary motion.
Herschel William
Herschel (1738-1822) was an amateur astronomer who built his own, very powerful telescope in his home in Bath, England. Until Herschel’s time, astronomers assumed there were just seven independent objects in the sky - the Moon, the Sun, and five planets. The five known planets were Mercury, Venus, Mars, Jupiter and Saturn. Uranus, the sixth planet, was discovered by William Herschel in 1781.William Herschel was one of the greatest astronomers. With the help of his sister Caroline, he discovered Uranus in 1781. He later identified two of the moons of Uranus and Saturn. At first, Herschel had thought that the dot of light he could see through his telescope was a star.
But when he looked more closely, he saw a tiny disc instead of a point of light. When he looked the next night, the ‘star’ had moved - this meant that it had to be a planet. Herschel wanted to name the planet George, after King George III, but Uranus was eventually chosen
’s partner in his discoveries was his sister Caroline (1750-1848), another great astronomer, who catalogued (listed) all the stars of the northern hemisphere. Herschel’s son John catalogued the stars of the southern hemisphere. Herschel himself added to the catalogue of nebulae. Herschel was also the first to explain that the Milky Way is our view of a galaxy shaped ‘like a grindstone’.
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