Syzygial Blog

Galileo Galilei (1564-1642).

Quotations from famous astronomers & scientists

Nicholas Copernicus (1473-1543).
'Finally we shall place the Sun himself at the center of the Universe. All this is suggested by the systematic procession of events and the harmony of the whole Universe, if only we face the facts, as they say, "with both eyes open".'
De Revolutionibus Orbium Coelestium (1543).
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Galileo Galilei (1564-1642).
'Philosophy is written in this grand book -I mean the universe - which stands continually open to our gaze, but it cannot be understood unless one first learns to comprehend the language and interpret the characters in which it is written. It is written in the language of mathematics, and its characters are triangles, circles and other geometrical figures, without which it is humanly impossible to understand a single word of it; without these, one is wandering about in a dark labyrinth.'
Il Saggiatore (1623).
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Sir Isaac Newton (1642-1727).
'If I have seen further (than you and Descartes) it is by standing upon the shoulders of Giants.'
Letter to Robert Hooke, Feb:5.1675.

'I do not know what I may appear to the world; but to myself I seem to have been only like a boy playing on the seashore, and diverting myself in now and then finding a smoother peeble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me.'
From BREWSTERS, Memoirs of Newton (1855).
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Sir James Jeans (1877-1946).
'Put three grains of sand inside a vast cathedral, and the cathedral will be more closely packed with sand than space is with stars.'

'All the pictures which science now draws of nature and which alone seem capable of according with observational fact are mathematical pictures.... From the intrinsic evidence of his creation, the Great Architect of the Universe now begins to appear as a pure mathematician.'
The Mysterious Universe.
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Sir Arthur Stanley Eddington (1882-1944).
'Man is slightly nearer to the atom than to the star.... From his central position man can survey the grandest works of Nature with the astronomer, or the minutest works with the physicist.'
Stars and Atoms (lecture 1928).
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Carl Sagan (1934-96).
'I would be very ashamed of my civilization if it did not try to find out if there is life in outer space.'

Aurorae
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Also known as Polar lights, are displays of rapidly varying, luminous coloured patterns seen in high latitudes, (Aurora Borealis in the northern hemisphere, Aurora Australis in the southern). The lights correspond to the red and green emission lines from atmospheric molecules, and nitrogen and oxygen atoms, which have been excited by energetic particles from the Sun. Aurorae normally occur at heights between 98 -110 km, and can take many forms. Glows, curtains, arcs or bands maybe tens of kilometres wide can extend to about 1,000 km in length, west to east direction. Activity is nearly permanent in the 'auroral ovals', which are ringed belts around the geomagnetic poles. Maximum activity at night is seen along the latitude of about 67 degrees, north and south. In N.Norway, Iceland, Northern Alaska and Canada, aurorae can be seen on an average of 240 nights per year.
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Ceres
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The first asteroid to be found and now known to be the largest, (about 950 km. diameter), was a lucky find by the Italian astronomer Giuseppe Piazzi (1746-1826). Seen while observing star positions from Palermo on 1st. January 1801. Piazzi named it Ceres after the goddess of Sicily, and he continued to observe it for several weeks until to close to the Sun. The mathematician Carl Gauss calculated where it would reappear, and on December 7th. 1801 Fritz von Zach found it again. Its mean orbital radius at 2.77 a.u. placed it neatly where the Titius- Bode law predicted (see Titius-Bode law).Ceres has a mass 1/3rd the total of all the asteroids (1x10^24g), is a greyish spherical body with a density of 2.7, and mean opposition magnitude of 7.3. A spaceprobe (DAWN) to Ceres and Vesta hopefully will be launched by NASA in 2006.
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Dawn to Vesta & Ceres
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Mission Profile

Launch from Cape Canaveral on a Delta 7925H is rescheduled for September 2007. After a few years heliocentric cruise including a Mars flyby in February of 2009, Dawn will reach Vesta in October 2011 and go into orbit for 7 months. One high orbit period at 700 km altitude is planned, followed by a low orbit of 120 km and possibly a much lower (15 - 75 km) orbit. Dawn will depart Vesta in May 2012 and reach Ceres in August 2015 where it will go into orbit for 5 months, a high orbit at 890 km and a low orbit of 140 km. Again, a final lower orbit at 50 - 75 km may be possible. The Ceres orbit phase will end in January 2016. It is expected that 288 kg of xenon will be required to reach Vesta and 89 kg to reach Ceres. The hydrazine thrusters will be used for orbit capture
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Kepler's Laws
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Johannes Kepler (1571-1630), German astronomer and mathematician. His three fundamental statements, derived empirically, about planetary motion, and based on the observations of the planets by Tycho Brahe (1546-1601).
1. The orbit of each planet is an ellipse with the Sun at one of the foci.
2. Each planet orbits the Sun such that the radius vector connecting the Sun and the planet sweeps out equal areas in equal times.
3. The squares of the sidereal periods of any two planets are proportional to the cubes of their mean distances from the Sun. T^2/r^3=constant.(ex:a hypothetical planet at 4a.u. from the Sun would take 8 years to complete one orbit. 4^3=8^2).
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Lunar Crater Plato
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The crater Plato is one of the superstars for observers of the Moon. It is big (101 km: wide), conspicuous with its dark floor ringed by a bright rim, and long a subject of detailed scrutiny, speculation, and controversy.
The view through a telescope is especially intriguing because of the irregularity of Plato's rim, as shown dramatically by variations in lengths of shadows cast onto its floor. According to old measurements reported in Thomas Gwyn Elger's 1895 book, 'The Moon', three peaks on the eastern rim rise 1.5, 1.8, and 2.1 km: above the floor. On the western rim an obvious, large triangular massif is partially disconnected from the crater rim. This 15-km-long block, and another one farther north, resulted from giant landslides, where segments of the rim slid slightly inward, creating a scallop - a bite out of the circular rim. Variations in rim height and width may thus be due to slumping, but the height differences on Plato's east rim must be of older, unknown origins.
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Lunar Eclipses
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A lunar eclipse occurs when the Moon passes into the shadow-cone of the Earth. It can only happen at full Moon and is visible from wherever the Moon has risen. The Moon usually remains partially visible, its disc illuminated, (often a deep reddish hue) by light scattered by the atmosphere of the Earth. The umbra (full shadow of the Earth) is surrounded by an area of partial shadow, called the penumbra. Some eclipses may be only penumbral. The 'magnitude' of a lunar eclipse is obtained by dividing the length of the Moon's path through the umbra, by the Moon's apparent diameter. The maximum number of eclipses in any one year, (Solar and Lunar) is 7, 2 or 3 of which must be lunar. However lunar eclipses at two successive full Moons are not possible. The diameter of the Earth's shadow-cone, at Moon's mean distance, is roughly 9,170km, and its length on average 1,367,650km.