Name __________________________________ Date ___________ Period ______
History of ASTRONOMY
Astronomy is the science that studies:
--the _________________,
--the _________________ of the objects found in space, and
--the laws under which the universe _________________.
The History of Astronomy
--The “______________ Age”
--600 BC – _____ AD
--Just based on: (1) ____________________of the sky and (2) philosophical
_____________________
--Supported by _______ where possible
--Aristotle
--Stated that the Earth is _____________.
--Used Earth’s __________ on the moon during an _________ as his argument.
--Eratosthenes
--Determined the ______________________ of Earth
--Pic:
--First of all, he knew the exact ____________ between 2 major Egyptian cities
( _________ & Alexandria)
--Next, using the shadow cast by the ______ at noon, he measured the
__________ of the sun at each
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--Why noon??
--The sun is the most ___________ overhead
--He found it easiest to calculate on the __________ solstice
because the angle was 0 at Syene (cast ____ shadow)
--The difference between these 2 angles was 7 degrees
--This is 1/50th of the ___________________ of a circle (7/360)
--What next??
--Assuming that the “circle” is the Earth’s circumference, then the
distance between the 2 cities is expected to be 1/50th of the
circumference of the Earth
--All he had to do was multiply that known distance by ______
--Only off by ______ miles!
--Other Helpful Greeks
--Aristarchus
--1st to suggest that the Earth _____________ the Sun
--Called ____________________ model
--_____________ by peers
--Hipparchus
--Created a star “_____________”
--Recorded the ________________ of ~ 850 stars
--Divided these stars into ____ categories based on their individual
________________ (will be significant later)
--Geocentric Model of the _____________
--First proposed by Ptolemy in 141 AD
--All objects revolve around the __________ in perfect __________
--The ______ is found between Venus & Mars
--The stars are ___________ in the heavens
--Also called the Ptolemaic _____________
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--Problems with Ptolemy
--The apparent __________________of the planets as they orbit vary as if
their distance from us is varying.
--Sometimes the planets appear to move ________________ in their path
across our sky.
--Called ___________________ ___________
--Ptolemy’s Solution
-- Each planet follows a ___________, circular orbit that is always
centered around its concentric orbit of Earth.
-- The smaller orbit is called its ____________.
-- The concentric orbit around Earth is referred to as its _____________.
--Pic:
--Ptolemy Gets Tricky
--Why are Mercury & Venus brighter when on one side of the Earth’s sky
vs. another?
--Does not support geocentric model
--The Renaissance 1300’s-1500’s
--Arabic Astronomy
--Named stars
--Used the ________________ to find Mecca
--2D model of the skies
--Used to make measurements of celestial objects & their position in the
skies
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Beginning of Modern Astronomy
--Nicolaus Copernicus (1543)
--Proposed the ___________________ model again
--Retrograde motion can be explained if _______ have varying ________ speeds
--Mercury & Venus revolve around the sun ___________ than we do
--They catch up and pass us, changing our __________________ of their
direction of motion
--The same effect happens as we revolve faster than the ________ planets
--Planet brightness is associated with its position ___________ to the sun!
--____________ to the sun = brighter
--Because we are not the _______ of the solar system, Earth does not ever
block the ______________ from Mercury & Venus
--Stellar Parallax
--Suggested that the stars are very _____ away
--Proposed that the Earth ____________
--Calculated relative distances to planets
--Problem with Copernicus
--If the planets revolve around the sun in perfect circles, we should be
able to precisely _____________ their positions. Right?
--Hmmm…..why do they seem to “stray”???
--Tycho Brahe (1546-1601)
--Built the 1st ___________________, but it did not use telescopes
--Proved that the heavens ____________
--New stars appear in the sky (star formation)
--Comets appear only briefly
--Galileo Galilei (1564-1642)
--First to use the _________________ to study the skies
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--Observed that the phases of the ________ support the belief that the
Earth rotates on its ______
--Noted that the _____________ of the moon is not _____________
--Discovered _____ _________ around Jupiter
--Observed these moons _____________ Jupiter
--Proved that OUR moon __________ _____
--Observed the “____________” of Venus
--Actually a result of its orbit around the ________
--The amount of the planet ____________ varies as it changes its
_____________ from its light source (the sun)
--_______ phase
--Venus _____ visible
--Coincides with the part of its orbit that tracts ___________
the sun, completely blocking its visibility
--Venus & Mercury must be __________ to the sun
--Other Discoveries
--Planets are circular disks that ____________ light
--Not “__________” of light, therefore they are not _______
--Sun has dark regions
--Called _______________
--Used to estimate the sun’s _________________ ___________
--Work proved ________________ right
--Condemned by the Church
--Johannes Kepler (1571-1630)
--Used Brahe’s data to correctly describe _____________ _________ in 3 Laws
--#1: Planets orbit the sun in _______________ paths, not perfect circles, and
the Sun is at 1 focus
--#2: The orbital speed of a planet is __________ the closer it is to the Sun
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--#3: The square of the orbital ___________ is proportional to the cube of the
average orbital __________
--Formula: (radius)3 = k * (period)2 where __ is a constant
--The further away the planet is from the sun, the longer it
takes to orbit it
--Use formula to determine those actual values
--Isaac Newton (1642-1727)
--First to test the Law of Universal ___________
--The greater the ________ of an object, the greater the gravitational
__________ it creates
--Proved that it’s actually the combination of ___________ (Galileo’s
original idea) and ___________ that results in the elliptical orbital shape
of planets
--Restated Kepler’s 3rd Law to include the ________ of the bodies
involved
--Calculated the Force of Gravity
--Invented the _______________ telescope, calculus, and physics
--Einstein
--Theory of Relativity
(1) All ________ distorts the ___________of space and time
--Larger masses = ____________ distortion
--Explains why light “___________” around massive objects like galaxies
--Space is ___________
--Bends light to a common focal point like a _______________
--Called __________________lens
--Allows us to see objects _________ away then we normally could
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(2) Time __________ as you approach a massive object
--A clock actually runs a fraction of a second ____________ at the top of
a tower as compared to the same clock on the ground
--Similarly, all clocks run slower as the earth moves ___________ to
the sun
--Closest = slowest = January
--What happens as the earth moves away again??
--Also affects _______
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