Download Celestial Motion

OUTCOME QUESTION(S):
S1-4-03:
Why were the position and motion of visible celestial
objects important to past cultures?
How can you measure the location of objects in the sky?
Vocabulary & Concepts
Constellation
Polaris
Star
Planet
The Science of Astronomy
• Astronomy is the study of the Universe
• Scientists who study Astronomy are known as Astronomers
• Like most scientists, Astronomers aim to answer specific questions
• What kind of questions do you think Astronomers are trying to answer?
The Science of Astronomy
• Astronomers differ from most other scientists in one
aspect…
• Unlike most scientists, Astronomers cannot actually touch
the objects they study because everything is so far away.
• This makes Astronomy an observational science rather than
an experimental science
Early History of Astronomy
• Ancient people saw seven celestial bodies moving through the stars:
1.
2.
3.
4.
5.
6.
7.
Sun
Moon
Mercury
Venus
Mars
Jupiter
Saturn
Early History of Astronomy
• 5 of these objects were
considered to be “special
stars” due to their
movement patterns.
• Ancient people called these
special stars planets.
Only five planets can be seen without
the naked eye…Which ones?
My Very Educated Master Just Showed
Us Nine Planets
1. Agricultural revolution: tracking stars became
necessary to accurately mark the growing season.
Position allowed for creation of a calendar that had
365 days in a year.
There was both a spiritual and
practical significance to tracking
the celestial movements
2. Exploration and Trade: tracking stars used to
navigate water for trade and conquest.
Stars and the Sun became the
"landmarks" used.
Groups of stars are “constellations”
• used to organize the sky
• named for animals and gods
Zodiac is Greek for “circle of
animals”
STONEHENGE
What is Up there?
Stars: very large collection of matter that emits an
intense amount of energy (light and heat).
Planets: collection of matter that is generally
spherical and revolves (orbits) around a star.
Our solar system:
A star (Sun) and all the objects orbiting it
Feature
Planet
Star
Location
In the solar system
Far beyond the solar
system
Distance from Earth
Fairly near
Very, very, very far
Real size
Smaller than most stars
Larger than planets
Reason we see it
Reflects light
Emits light
Surface temperature
Cold or very cool
Very hot
Composition
Rocks and/or gases
Gases
Look
A constant light
Twinkles / flickers
Motion over time
Very slowly wanders
through constellations
Move only as part
of a constellation
Scientists estimate our solar system is 4.6 billions years old
CAN YOU ANSWER THESE QUESTIONS?
S1-4-03:
Why were the position and motion of visible celestial
objects important to past cultures?
How can you measure the location of objects in the sky?
Vocabulary & Concepts
Constellation
Polaris
Star
Planet
OUTCOME QUESTION(S):
S1-4-04:
How was the process of science important in showing the
Sun is the centre of our solar system?
S1-4-05:
How does the position and motion of Earth produce
day/night, the phases of the moon, and the seasons?
Vocabulary & Concepts
Ptolemy
Copernicus
Galileo
Kepler
Retrograde
Celestial Motion:
Ptolemy (100 AD)
• Hypothesized “epicycles” to explain observations
and knowledge of that time
• Earth was centre of the universe - Geocentric
• In good with the Church
Planet is Greek for “wanderer”
Observation:
Some planets seem to
move backwards in orbits:
“Retrograde motion”
Copernicus (1473)
• Produced mathematical evidence for a Suncentered system – heliocentric
• Much simpler explanation for retrograde motion
• Hypothesized Earth rotated on axis once daily and
revolved around Sun once yearly
• Not in good with Church
Called the “Founder of
modern astronomy”
Galileo (1564)
• Perfected the telescope (built a few years earlier)
• First to state and use the scientific method
• Discovered moons around Jupiter
1 Proof that not all objects traveled around Earth
• Venus had phases (day/night) like Earth/moon
2 Proof that it traveled around the Sun
• Not in good with the Church
Galileo’s
drawings and
scientific
records of his
observations
Galileo published his evidence
confirming Copernicus’ mathematics,
and was accused of heresy by the
Church.
• Would not recant his work as a mistake and
spent entire life under house arrest
By the way, Pope John Paul II made a public
apology and exonerated Galileo in 1992
Kepler (1571)
• Worked as assistant for astronomer, Tycho Brahe
Brahe’s goal was to prove Copernicus incorrect
• Brahe
builtloads
one ofofmoney
the best
He received
from the
Church in hopesin
hethe
could
prove the
observatories
world
Earth-centred view…he failed
• Measured positions of 777
stars and five planets that were
known at that time
Kepler used Brahe’s data after his death to describe
three laws of planetary motion:
1. Planets orbit the Sun in ellipses (not circles)
2. Planets move faster close to Sun, slower farther away
3. Planets farther away have a longer orbital period
What do we know today?
The Earth rotates on its axis once a day.
At any time - half of Earth is in “day” and half in “night.”
Earth rotates towards the East
winter
summer
The Earth revolves around the Sun once a year.
At any time - half of Earth is in “winter” and half in “summer.”
Our axis is tilted at 23.5o (degrees)
This tilt and the curvature of the Earth is
responsible for the variations in the Sun’s energy
– and creates our seasons.
Summer: not only more “direct” but also more hours of the
Sun’s energy
Spring Equinox
(Mar 21)
12h and 12h
Summer
Solstice
Summer
(Juneenergy
21)
“direct”
Longest Day
Winter
Solstice
Winter
(Dec energy
21)
“indirect”
Shortest Day
Fall Equinox
(Sept 22)
12h and 12h
Moon Rotation
• Moon completes 1 rotation on its axis in the
same time as it completes 1 revolution around
the Earth (synchronous)
• We always see the same side facing the Earth
That’s why there is a “dark side” of the Moon
• Orbit is elliptical
• Tilted 5°
• Mean Distance:
384,400 km
Phases of the Moon
• Shines only by reflected sunlight
• Depends on fraction of sunlit half visible to us
The North Star – Polaris – is used for navigation.
• Polaris is due north How high Polaris is in the
sky (altitude) equals your latitude on the earth's
surface.
What do people in
the Southern
hemisphere use?
LAND coordinates are called latitude and longitude.
This is Winnipeg
Measuring Angles in the Sky
Astrolabe
• Instrument used to calculate the position of
objects in the sky with high accuracy
• Perfected during Islamic Golden Age (800-1200s)
• Period of enormous growth in math, science and
medicine
Vertical (up/down) angle is called altitude:
Horizon – ground - 0°
Zenith – directly above - 90°
Horizontal (left/right) angle is called azimuth:
(measured with a compass)
North – azimuth of 0°
South – azimuth of 180°
altitude
azimuth
A position
in the SKY is given using altitude
and azimuth as
its “coordinates”
CAN YOU ANSWER THESE QUESTIONS?
S1-4-04:
How was the process of science important in showing the
Sun is the centre of our solar system?
S1-4-05:
How does the position and motion of Earth produce
day/night, the phases of the moon, and the seasons?
Vocabulary & Concepts
Ptolemy
Copernicus
Galileo
Kepler
Retrograde
Geocentric Heliocentric
Solstice