SciRev. X102 Exam 3 wk. 9 astronomy with expert curated questions and answers

what was an instrument for discovering marvels in the heavens (17th century)?

-the telescope

-new stars, satellites around jupiter and saturn, saturn's rings, features on the moon and sun

telescope in the 18th century

-largely became an instrument for postitional astronomy, to accurately measure the positions of stars and other celestial bodies, such as the moon

3 tests of Newton's universal gravity

-shape of the earth

-observed motion of the moon

-periodicity of comets

shape of the earth

-had to be determined whether it is flattened at the poles as predicted by newton (he was right)

-Maupertuis

Maupertuis

-polar expedition

-w/ Clairaut and Ander Celsius

-measured earth's meridian at different latitudes

-measured their arc in the winter month below the Arctic circle

-found that the earth was slightly flattened at the poles

-"the man who flattened the earth"

observed motion of the moon

-involved perturbations that seemed double what newton had predicted relying on universal gravity

-clairaut

Clairaut and the moon

-announced that newton's laws didn't account for the moon

-calculating the moon's motion required three bodies mutually attracting each other

-found the moon differed month to month from the predicted value by 2

-moon is attracted strongly by two bodies, the earth and the sun, pulling at different angles to one another

-clairaut announced that newton was right all along nd that all perturbations relied on the inverse-square law

periodicity of comets

-had never been proved and had to be established observationally

-looked at Halley's comet bc it came around every 75 years or so so more observations could be done on it

-Halley predicted the return of the comet

-newton predicted that comets moved along conic sections (Halley and clairaut proved him right)

James Bradley

-discovered two major phenomena: aberration of light and nutation of the earth's axis

-both were tiny effects requiring extremely accurate and long-term observations

aberration of light

-we tilt our telescopes forward by an angle related to the ratio btw the speeds of light and of the earth

-implicitly proves the earth's motion

-was discovered when he noticed that the "fixed" stars would reach as much as 20 arc seconds

Bradley's nutation

-is a wobble of the earth's axis w/ a period of 18.6 years due to the perturbation of the moon

-noticed there were fluctuations of about 7 arc seconds which was caused from the wobble

precession of the equinoxes

change in orientation of a rotational axis w/ respect to a reference plane

Tobais Meyer

-produced the best lunar map and lunar tables of the time (to w/in 1 degree)

-lunar motion was crucial for determining the longitude at sea, using the moon's motino as a clock against the background of the stars

-after he died, his wife received 3,000 from the british admiralty

John Harrison

-built many superior chronometers that won him 20,000

-helps find the longitude at sea through acurate time keeping

-one problem was that each watch had its 'own rate of going' in which it would steadily gain o lose small amount each week. (once this was fixed, longitude could be calculated)

Captain James Cook

-3 journeys to the pacific led to hugely improved maps from australia to new zealand to the bering straight and hawaii

Cook's first journey

-sent to find the elusive continent (australia)

-when they were repairing 'the endeavor' they sketched a kangaroo

-ran into eastern shore of austrlia and called it new south whales

-used the lunar method to determine longitude

-angular distance btw the moon and celestial objects

cook's second voyage

-he carried three chronometers (made by Arnold) and one made by Kendall

-also had the nautical almanac

-was to seek the southern continent

-got below 71 S

-circumnavigated Antarctica w/out seeing it (as ice was blocking it) ('resolution' ship)

nautical almanc

-Maskelyne

-method of finding longitude by accurately observing the distance btw the sun and the moon and then consulting tables

Cook's third voyage

-died in hawaii

-showed an extreme example of unfortunate cross-cultural contact

-carried a replica of harrison's chronometer to determine latitude

Frederick William Herschel

-and his sister Caroline

-relied on a giant reflecting telescope w/ a mirror

-discovered a new planet, uranus, moving beyond the orbit of saturn

-was the first scovery of a new planet since antiquity

-mapped the milky way and discovered a huge number of non-stellar objects tht he called nebulae