Transcript History of Astronomy

The History Of Astronomy
Ancient times (Before 3000 B.C):
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People believed that the earth is Flat and that
astronomical bodies pass beneath Earth at night
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Some cultures were interested in astronomical events,
as evidenced by stone structures that were designed
to match up with solstices (Carnac, Newgrange Tomb,
Stonehenge, Giza Pyramids & Sphynx)
Newgrange Tomb, Ireland
Stonehenge, England
Babylonians (3000 BC)
• Mathematical theory rather than just observations
• Motions of the sun and moon
• Provided the first evidence that the earth is round
• Developed basic constellations and astrology
• Introduced the 24 hour day
• Developed a lunar calendar
Aristotle (384 BC – 322 BC)
Geocentric Theory
• Proved that the earth is
spherical
• Believed that the earth is the
center of the solar system and
that everything revolves
around it
• Believed that all stars are fixed
points which rotate on a single
celestial sphere
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Aristotle believed there were only a few basic
Substances
1. Earthly Realm – Air, Earth, Fire, and Water
2. Heavenly Realm – Quintessence (Not found on
Earth)
Aristotle agreed that the Earth is spherical BUT didn’t
believe that the earth moved.
1. No Rotation- NO sense of motion...no strong
winds…..No displacement of thrown object.
2. No Revolution – No measureable stellar parallax,
BUT the stars were too far away to measure
stellar parallax back then. They needed better
equipment.
The soul passing into quintessence
Stellar Parallax – Aristotle said that if the earth
revolved, the closer stars should shift among the
background of further stars. They actually do shift
but not enough for ancient astronomers to detect.
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Aristarchus (310-230 B.C.)
• 1st to place the sun at the center of the universe,
but his ideas were to radical for anyone to accept.
• 1750 years BEFORE Copernicus!
Eratosthenes (276 - 195 B.C.)
• 1st person able to measure the circumference of
the Earth
Hipparchus (190-120 B.C.)
• Compiled first star catalog
• Developed a scale for star brightness
• Accurately calculated distance from Earth to the
moon!
Ptolemy (90 – 168 AD)
• Earth-centered model which included a complex
system of Epicycles and perfect circles for the orbits
of planets, sun, and moon around Earth
• Assumed that the imperfect Earth was surrounded
by perfect heavenly spheres
Ptolomy’s model
worked so well, it
was not challenged
for 1300 years!
Copernicus (1473-1543, Poland)
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Popularized the suncentered, “heliocentric”
model of universe
• Stated that the earth spins
once per day on its axis
and revolves around the
sun in one year
• Published in Des
Revolutionibus in 1543 (on
his death bed)
The Heliocentric Model
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Sun at center of
universe
• Planets orbit sun in
perfect circles
• Stars on a huge fixed
sphere (the firmament)
More Copernicus
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Explained retrograde motion using passing orbits
Correctly ordered planets, and calculated their
distances!
Correctly calculated time for planets to orbit sun
Explained apparent motion of stars and sun using
Earth’s rotation and orbit
Explained why Mercury and Venus are always
seen near the Sun
Invented idea of Astronomical Unit (A.U.) –
Distance of Earth from the Sun (About 93 million
miles)
Distances of Planets from the Sun
Planets
Copernicus
Modern
Mercury
Venus
Earth
Mars
Jupiter
Saturn
0.38
0.72
1.00
1.52
5.22
9.18
0.387
0.723
1.00
1.52
5.20
9.54
Distances Measured In Astronomical Units (A.U.)
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Tycho Brahe (Teeko Bra-hay) (1546 - 1601)
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A Danish nobleman
Believed in geocentric model of solar system
designed and built accurate and powerful
instruments to observe the stars
used these instruments to chart the positions of
planets and other celestial objects with great
precision
disproved many of the commonly held notions of
planetary and stellar motion
Difficult to work with. He wasn’t very nice :-\
Died of a burst bladder (yukko!)
Johannes Kepler (1571- 1630)
• Worked with Tycho Brahe and kept his equipment and
notes
• Proposed that orbits of planets are ellipses, not circles
• Developed 3 simple laws to explain planetary motion in
1609
** 1st law- Orbit of all planets are ellipses with the
sun at one focus
** 2nd law – Law of Equal Areas which defines
planetary speed as they go around the Sun
** 3rd law – As planet distance from the Sun
increases, orbital period increases
Kepler’s 1st Law of Planetary Motion
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The orbit of a planet is an ellipse, with
the sun at one focus.
Kepler’s 2nd Law of Planetary Motion
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When a planet is nearer the sun in its
orbit (perihelion), it moves faster. When
it’s farther from the sun (aphelion), it
moves slower.
Autumnal Equinox (beg. of fall)
July
Winter solstice
(beg. of winter)
Fall
Summer
Winter
Spring
Summer
solstice
(beg. of
summer)
January
Vernal equinox
(beg. of spring)
Kepler’s 3rd Law of Planetary Motion
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The larger the planet’s orbit, the longer it
takes.
Planet, etc.
Mercury
Venus
Distance
0.39 AU
0.72 AU
Period
88 days
225 days
Earth
Mars
Jupiter
1.00 AU
1.5 AU
5.2 AU
365 days
687 days
11.9 years
Saturn
9.5 AU
Halley’s Comet ~ 17 AU
29.4 years
76 years
Galileo Galilee (1564–1642, Italy)
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Father of observational
astronomy
• 1st to publish in
Italian…Not Latin!
• While he did not invent the
telescope, he was the first
to use the telescope for
astronomy
Galileo’s Astronomical Accomplishments
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Redesigned the telescope
to be suited for observing
the sky (only 14X
magnification)
• Discovered that there
were many stars not
visible to the naked eye
More Galileo
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Discovered mountains,
craters, and plains on
Moon
Discovered phases of
Venus similar to the
moon
And More Galileo
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Discovered sunspots on
Sun
Still More Galileo
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Discovered 4 moons
orbiting Jupiter
Progress at Personal Cost
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Placed under house arrest by Catholic
Church and made to confess “vainglorious
ambition” and mistakes of “pure ignorance”
(aka – renounce Copernicanism)
• Not all religious: some political and
personal rivalries, too
• Worked on laws of motion and falling
bodies until his death (8 years later)
Phases of Venus….Evidence for a Heliocentric Solar system
Isaac Newton (1642-1727, England)
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Not expected to live
over a few
hours…instead lived
84 years and 3
months
Served as England’s
“Master of the Mint”
Knighted in 1705
Newton’s Contributions
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Invented calculus (at age 23!)
Realized that “white light” can be broken
down into colors of rainbow using a
prism (age 30)
Invented reflecting (mirror-based)
telescope, a great improvement over
Galileo’s refracting (lens-based)
telescope
More Newton
Mathematically derived Kepler’s 3 Laws.
• Calculated the existence of other planets due to
orbital anomalies of outer known planets
• Law of Gravity:
• Gravity exists between any 2 objects that have
mass
• Gravity is always attractive, never repulsive
• Gravity increases with increasing mass
• Gravity decreases with increasing distance
• 3 Laws of Motion
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Newton’s 1st law applied to Planets
Albert Einstein (1879 – 1955 A.D.)
Came up with many theories which expanded our
understanding of the universe
a.
Space and time are not separate units but
rather one unit called space-time
b.
Gravity is the curvature of space-time. The more
massive the object, the greater the curvature.
(This is the basis of Einstein’s General Relativity
Theory)
*** Einstein explained the true nature of gravity.
• That it’s not a force but a pathway that a mass takes around
more massive objects. This theory was proven correct by
the deflection of starlight observed during a 1919 eclipse.
c.
Most Famous for the Equation E=mc2 which led
to the development of the atomic bomb
Einstein’s Theory of Relativity
Edwin Hubble (1889 - 1953)
• determined that so-called “spiral nebulae”
were, in fact, other galaxies, proving that
the Universe extends well beyond our own
galaxy.
• showed that these other galaxies were
moving away at speeds proportional to
their distances away form us.
Georges Lemaître : (1894 – 1966):
• Belgian priest, astronomer and physics professor
• proposed the theory of the expansion of the
Universe, widely misattributed to Edwin Hubble.
• derived what is now known as the Hubble's law
and made the first estimation of what is now
called the Hubble constant which he published in
1927, two years before Hubble's article.
• proposed what became known as the Big Bang
theory of the origin of the Universe
Stephen Hawking (1942 - ):
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Combined the theories of general relativity and
quantum physics to prove that black holes emit
radiation
• Has written several books that explain complicated
subjects in astronomy, physics, and cosmology to
the general public.
• Completely paralyzed due to ALS, yet his computer
generated voice is very famous.