History of Astronomy Notes.docx

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Natural Science
NATS 1745
Mary- Helen Armour

January 6 2012- Navigation -Navigation and time are the methods of finding where you are on Earth -Looking at the stars, farther north-star is more over the head; further south-star is more towards the horizon -How do you determine how east or west you are? -Latitude and Longitude to determine your position -Once you were out of sight of land, navigation was very tricky because you dont where you have to go and you dont have any co-ordinates -Toronto is 79 degrees west -Things rise in the East, set in the West -You need very accurate time keeping and accurate positions in the sky -Galileo discovered how to use the motion and eclipsing of these moons to determine the longitude -Eclipses of the moon give you this ability, if you coordinate the relative position in the moon you could determine your longitude; however not practical to wait for an eclipse - Finding longitude is all about finding time, ex. Time difference between Toronto and London or Vancouver -As the sun progresses across the Earth, it takes 1 hour to travel 15 degrees longitude -Every aspect of longitude requires time, its all about telling time in two different positions -June 16 1740, British Parliament forms Board of Longitude -Board offered a prize, 10 000 pounds to anyone who could measure the longitude within 1 degree accuracy or 20 000 pounds if it could be measured within a half a degree accuracy -Two methods derived from this Chronometers- Just clocks; you had to make a clock that could tell time very accurately, clocks were not that very accurate, you had to set your clock according to the position of the sun Lunar Distance Method- Using the position of the moon and other objects in the sky to tell the time without the mechanical chronometer -Greenwich, England is the 0 degree longitude -Globe is 360 degrees, 24 hours each day, it takes 1 hour for the sun to travel 15 degrees -Local time is compared to a standard time (Greenwich) -In 16 century, start plotting accurate star charts -Flamsteed produced the first set of star charts with the use of the telescope and plots roughly 3000 stars in the Northern Hemisphere Lunar Distance Method The other technique (referred to as the lunar distance method) was much more complex and involved using the moon as a clock. The moon moves fast enough, that it will move its own diameter in one hours. As it moves through the background of stars, it could mark time locally based on its position relative to other stars To use this method a navigator would need: 1.accurate positions of moon compiled into detailed tables. 2.need at the location to take detailed measurement to compare to the tables. 3.need accurate positions of the background stars as well. January 13 - Expanding the Solar System -All astronomy was doing prior to Galileo was plotting positions in the sky -There was no understanding of why things were as they were -Expansion of the solar system starts with Galileos discovery of Jupiters moons -Looking at Saturn, you can see that Saturn changes shape -Hoygins discovers the rings of Saturn and how they existed -Hoygins and his brothers are telescope makers, although most people were building their own -The rings of Saturn are very thin, roughly 100m thin -As Saturn tilts, astronomers could see the rings, it would have to be on an angle -Hoygins was Dutch, works in the Paris Observatory and works on trying to discover timepieces -Cassini, the first head of the Paris Observatory was Italian -He realizes that Saturns rings are not solid, and are rather a series of rings which have different compositions and distances from Saturn -Comets are found more often with the telescope -On average 2-3 comets enter the solar system every month -The shortest comet orbit is roughly 3-5 years -Many comets due return regularly -Comet hunting began to be established as a branch of astronomy in the mid 1700s -Once you spot a comet you could watch its orbit through days, moths etc. -Ideal way of spotting comets is tacking pictures of the night sky on a daily basis and comparing the differences of each picture -Charles Messier, French, known for the Messier catalogue -Comets look like fuzzy glowing patches in the sky, not all of these patches were moving. Messier set out to create a catalogue marking the patches that did not move -He found roughly 110-115 objects in first catalogue -William Herschel looked at the catalogue and sought out what were these objects if they were not stars -Into the late 1700s, people were trying to explain the spacing of these planets -In 1781, Herschel accidentally discovers the planet Uranus -Bodes law-It is a mathematical relationship between the separations of the planets. Bode proposed this law around 1778. -In 1801, another astronomer - Piazza, in the course of compiling a stellar catalogue, stumbled across a object in the part of the solar system, Bodes law suggest this object should be at. Piazza named this object Ceres. This object fit the bill to be the missing planet, except it was relatively small -In the next several years, many more asteroids were found -Herschel observed these objects, and quickly realized that they were too small to be a planet, they are significantly smaller than even our own moon and he was one of the first to suggest instead that these were fragments of a larger object that had been destroyed. This theory is wrong. -The asteroid belt is not a destroyed planet -Further planets did not fit the actuality of the spacing. All the planets up to Uranus were fairly accurate, after that it was off -Neptune did not fit in with bodes law -Neptunes existence was suspected before it was even found -Jupiter and Saturn are so massive that when they approach each other that contrast from one another -In the case of Mercury, a planet even closer to the sun called Vulcan was speculated to exist to explain certain orbital irregularities. Despite many searches, no such object was found (the distortions are actually caused by general realistic effects - Einsteins worked this out later). -Uranus takes 80 years to go around the sun -Based on these observations two other groups of astronomers began searches and it September of 1846 Neptune was located, it was between the positions calculated by Adams and LeVerrier. -Looking back at the historical records it was realized that Neptune had actually been observed several times before. This includes observations by Galileo in Dec. 1612, and John Herschel in July 1830, but neither realized it was actually a planet they were seeing. -Through several observation, they were able to figure out Neptunes orbit which is roughly 160 years. -Percival Lowell is involved in discoveries about Mars and Pluto -Comes from a rich family and is capable of building his own telescope -Light and weather is key in observing the solar system, clear conditions is necessary -Most contemporary research materials are found on mountains or areas with high elevation; enables you to specify in certain areas - Lowell became interested in Mars after seeing the maps produced by Schiaperelli in 1877. Schiaperelli describes some of the features he sees as canali this is the Italian word for channels (natural formation), but Lowell misinterprets this as canals which are an artificial structure. Lowell spends the next years making detailed maps of Mars. Mars changes colour with the seasons and the polar caps visibly melt and refreeze. -Mars changes colours according to the seasons -Mars is darker in the summer, lighter in winter; In Canada, lighter in winter because of snow, darker in the summer because the growing of crops. He assumed that crops were also growing on Mars -Lowell came up with a theory of Martian civilization -Most of Mars surface is carbon dioxide; the change in colours due to season is a result of dust storms -Lowell also speculated on the existence of Planet X - another planet beyond the orbit of Neptune. A variety of different scientist had made calculations that suggested there should be a ninth planet. Lowell did extensive searches looking for this object but never found it. -There is another asteroid belt just inside the solar system with Pluto being one of the objects in it -There are currently 8 planets in our Solar System -What is a Planet? The basic requirements are 1. it orbits the sun 2. it has sufficient mass to be spherical in shape (this is due to gravity) 3. it has cleared its planetary orbit of other objects Since Pluto and a few others do not meet the 3rd criteria they are defined as dwarf planets Any object that only meets the first criteria is now referred to as a small solar system body (like asteroids, comets etc.) In the late 18th century, Chladni, suggests that meteors are associated with the asteroids, and are pieces of them that fall from the sky. In 1803 an individual called Biot, works out the fall trajectories of a meteor shower, and proves they are elliptical which is the expected pattern for objects falling from the sky. In the early 1800s (1832),the comet Temple- Tuttle (which has a 33 year orbit) passed Earth. The Leonid meteor shower peaked the next year in 1833. For looking at the records, it was realized that the shower peaked every 33 years, just after the comet had passes. This brought the realization that meteor showers are caused by comets. The comet leaves behind debris in Earth orbit, and later the planet passes through this debris producing these showers January 27 2012 Stars th -In the 19 century, we get a better understanding of light; telescopes collect light -Isaac Newton starts to look into the nature of light -Light is both a wave and a particle simultaneously -Colour is a fundamental property of light -You cannot change the colour of light; if it is red light, it will always be red light
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