cycles of the sky - mctcteach€¦ · • astrology is based on the locations of the constellations...
TRANSCRIPT
Study Points• Predict the approximate time of day/night you should look for first quarter moon, full moon,
last quarter moon.
• Explain how astronomers think the Moon formed and give evidence.
• What causes a solar eclipse? What causes a lunar eclipse? What phase is the moon for each?
• Explain why the Earth undergoes seasons. Explain why it is hot in the summer. Explain why the Sun appears high in the sky during the summer but low in winter?
• What is included in the area of the sky known as the zodiac? What does the word zodiac mean? How many constellations are in the zodiac according to astronomy?
• What is the ecliptic plane? Where is the Sun in this plane? the Moon? the planets? the stars?
• What is meant by “the Sun is in Leo”? Explain why you only see some of the constellations of the zodiac at a given time.
• What is meant by the Earth’s precession? Is Earth’s precession a long or a short time?
• Explain why Polaris is the North Star? Explain why the stars appear to revolve around the North Star?
• Explain why the Sun is not in the constellation horoscopes say it is in when you are born.
• What distinguishes science from non-science? Give an example.
• Name the five North Circumpolar Constellations. Why are these important to us in MN?
• Define equinox and solstice? Sketch the Sun, Earth, and Earth’s orbit. Draw Earth with the axis tilt and label the location of Earth at the solstices and equinoxes.
Cycles of the Sky: Part 2
• Moon
– Moon Phases, Motions, Formation
– Lunar and Solar Eclipses
• Zodiac, Ecliptic
• Precession
• North Circumpolar Constellations
• Seasons
Moon Phases
Orerry with light
Moon Phases*
Moon Position at Sunset*
Moon Phases Continued*
Moon Position at Sunrise*
Moon rises ~50 minutes later every day
From Last Moon Lecture
Conclusion on Moon’s motion:
• Minute to minute the Sun, Moon, & stars
appear to rise in east and set in west due
to Earth’s spin (rotation).
• Day to day, Moon moves west to east due
to Moon’s orbit (revolution) around Earth. (Also generally true for other planets, due to the planet’s
orbit.)
On Earth the Sun, Moon & stars (generally) rise in the east
and set in the west because of Earth’s rotation (spin).
WESTEAST
Moon Motion in
One Day (~minute to minute)
Moon Motion Day to Day
Day to day from Earth, the Moon moves EAST because of
the Moon’s revolution (orbit) around Earth.
Moon Revolves
~12 deg/dayMoon
Moon’s
Orbit
Earth East
West
Origin of Moon*• Early Earth and Mars-size object collide*
– Mars-size object known as Thea
• Moon formed out of particles orbiting around the
new collided Earth*
• Moon is made up of materials found in Earth’s
crust (outer layer)
• Watch: How the Moon was formed https://www.youtube.com/watch?v=mQAdYWcA7ig (1:56)
• Watch: Evolution of the Moon (after it formed) https://www.youtube.com/watch?v=UIKmSQqp8wY (2:41)
Image: http://www.seti.org/node/1458
Lunar Eclipses – only at Full Moon*
•If the Moon passes
through Earth’s
shadow, we see a
lunar eclipse.*
•Lunar Eclipse – Earth
blocks the sunlight
from the Moon*
• If the entire surface
of the Moon enters
the umbra, the lunar
eclipse is total.
© Cengage Learning 2014 Orerry with light
Total Lunar Eclipse
• A total lunar eclipse can last up to 1 hour and 40
minutes.
• During a total eclipse, the Moon has a faint, red
glow, reflecting sunlight scattered in the Earth’s
atmosphere.
Lunar Eclipse
Dates• 1 – 2 lunar eclipses
per year usually
• Next one in MN:
May 16, 2022
Total Lunar Eclipse visible from Minneapolis
1/20-21/2019, 9:33pm to 12:50amWatch: Great Video of January Lunar Eclipse
https://www.timeanddate.com/eclipse/in/usa/minneapolis?iso=20190121
Size of the Sun & Moon from Earth
• From Earth
the size of
the Moon
and Sun
are about
the same!
The angular diameter of the Moon (~0.5o) is
almost exactly the same as that of the Sun.
This is a pure coincidence. The Moon’s linear
diameter is much smaller than that of the Sun.
Solar Eclipses – only at New Moon*
Due to the equal angular diameters, the Moon can
cover the Sun completely when it passes in front of
the Sun, causing a total solar eclipse.*
Solar Eclipse – Moon blocks Sunlight from Earth*
Orerry
with
light
Solar Eclipses
The Moon’s shadow sweeps
across the Earth, over points
from where we can see a
solar eclipse.
Total Solar Eclipse
During a total solar eclipse, the solar
chromosphere, corona, and
prominences can be seen.
Diamond
Ring Effect
Solar Eclipse Types
1. Total 2. Annular 3. Partial
4. Hybrid (both total and annular)• Types are due to the changing (angular) size of the
Moon and Sun seen from Earth because the orbits are
not perfect circles (they are ellipses). Wikipedia.com
Solar Eclipse Dates
• About 1 per year; max time is ~7 min
• Next Total Solar Eclipse in USA (TX
to ME): April 8, 2024
– 2033 Alaska; 2044 MT & ND
• Last Total Solar Eclipse across USA
– August 21, 2017 (OR to SC)
– Look at Best Pictures: website link
Very Important Warning:Never observe the Sun directly with your bare
eyes, not even during a partial solar eclipse!
Use specially
designed solar
viewing shades,
solar filters, or a
projection
technique.
Constellations
• Imaginary memory aids to describe sky
• 88 total constellations named in Earth’s
celestial sphere (previously 48 from
Ptolemy about 350 BC)
• Other versions around the world –
Japanese, Chinese, Arabic, Hindu, Native
American
Celestial Sphere
Zodiac Constellations
and the Ecliptic
Zodiac means circle of little animals*http://lifeng.lamost.org/courses/astrotoday/CHAISSON/AT301/HTML/AT30103.HTM
Constellations of the Zodiac
• Seen throughout the year because of Earth’s revolution
• The zodiac constellations are located along the Sun’s
path on Earth (Ecliptic Plane).*
• Ecliptic Plane – the plane of Earth’s path around the
Sun.*
• The zodiac region includes the Earth’s path around the
Sun, our Moon’s path, & planets’ paths across Earth’s
sky.*
Annual Motion of the Sun
• The Sun is in Sagittarius on January 1 (sign of Sagittarius)
• The Sun is in Aquarius on March 1 (sign of Aquarius)
• The Sun is in Leo on September 1 (sign of Leo)*
• During the days of a given zodiac sign, that constellation isn’t
visible because it is behind the Sun, as viewed from Earth*Orerry with Sagittarius
Two Versions of Zodiac
Constellations
One constellation missing from the traditional zodiac signs.
http://spaceplace.nasa.gov/starfinder2/en/
• 13 Astronomical
Constellations of the
Zodiac (used by
astronomers) and
includes Ophiuchus*
• 12 Astrological
Constellations of the
Zodiac
• All 13 are in the
ecliptic plane;
Babylonians removed
1 to fit the 12 month
calendar
Precession of Earth• Earth’s Precession – slow movement of Earth’s axis because
Earth is spinning* (traces out a circle as it changes)
• The Earth’s North pole currently points to Polaris so we call
Polaris our North Star, but the North Star will change.*
– Earth’s axis of rotation points to the North Star and stars move around
that point as the Earth rotates
• 3000 BC: North star = Thuban (5000 years ago)
– origin of astrology about 1000 BC, different sign dates (3000 years ago)
• 14,000 AD: North star = Vega (12,000 years in the future)
• 26,000 year cycle (long time)*
Parke Kunkle’s
precession
video(watch if you
miss lecture)Precession wheel demo
What Sign Are you?
• Astrology is based on the locations of the constellations from
about 3000 years ago when the constellations were visible at
different times of the year than they are now.*
• Astrology is not a science; it is a belief system – not testable or
repeatable (science hallmarks: natural, testable & simple)*
• Astronomy uses the same names of constellations and uses all
13 constellations in the ecliptic
• You can look up your astrology sign based on the 13 sidereal
constellations and accurate north star here: http://www.livescience.com/4667-astrological-sign.html
• More about this from NASA here: http://spaceplace.nasa.gov/starfinder2/en/
Discuss
• What do you think of astrology signs? Are
they accurate? Or do they take advantage
of human weakness to want to find truth in
something?
North Circumpolar Constellations• Constellations visible year-round (mid-latitudes & north)*
– Minnesota and further north to the North Pole
• Don’t rise or set; Visible all year and all night
• 5 North Circumpolar Constellations: Ursa Major (Big Dipper),
Ursa Minor (Little Dipper), Cassiopeia, Draco, Cepheus*
Globe & Celestial Sphere
http://antwrp.gsfc.nasa.g
ov/apod/ap040911.htmlhttp://www.captureminnesota.com/
Seasons on Earth
Northern summer =
Southern winter
Northern winter =
Southern summer
• Caused by Earth’s tilt which is about 23 degrees
Globe
Seasons• When the northern hemisphere is tilted toward the sun, it
also experiences longer daylight.
– Longer daylight is the cause of higher temperatures in summer*
• The Earth’s tilt causes longer daylight in one hemisphere
– Show longer daylight with globe & Sun is higher in the sky
www.faculty.edfac.usyd.edu.au
• Equinox: equal night and
day*
• Equinox is when the Sun
is crossing Earth’s
equator*
• Solstice: daylight is
longest in each
hemisphere*
• Solstice is when Earth’s
axis is tilted toward the
Sun in one hemisphere*
Fall
Spring
Summer
Winter
Northern Hemisphere
Seasons
Orerry
Explanation with a friend
• Explain why the Earth undergoes seasons. Explain why it is hot in the summer. Explain why the Sun appears high in the sky during the summer but low in winter?
• Write your own explanation with the help of a classmate. Write 2-4 sentences to explain.
• This will help you understand what you learned today.
Planetarium Observation• Planetarium Start Jan. 28; Due May 5 (10 points) Go to a
planetarium show
• Best Option: Como Planetarium Class Field Trip on Tuesday,
Feb. 4. (FREE!) at Como Elementary School– Bus from Minneapolis College at 8:15am from the corner of Spruce
Place & Harmon Place on the south side of Science bldg., by T bldg.
Bus returns by 10:30am.
– Free show at 9am this day only.
– You can drive on your own but you need to be early because the door
will be locked. Address: 780 West Wheelock Parkway, St. Paul, MN
• If you do not go to the Como Planetarium with the class, then
you can go any time on your own at your own cost – you pay.
See the link at the top for options:– Como Planetarium Tuesdays at 7pm usually – see their calendar
– Bell Museum throughout the week
– Jackson Middle School classroom planetarium
– Make a Shoebox Planetarium
You only need to do this once. If you go to Como on Feb. 4, then there is
no need to do any more for this.
• Continue flashcards of STUDY POINTS
• Do D2L Brightspace Quizzes 1 – 2
• Come prepared to Lab this week
• Test 1 in 2 weeks, Tuesday, Feb. 11
– To prepare: study points & 4 D2L Brightspace quizzes
– About 60 multiple choice questions. Bring a pencil.
– Optional: bring calculator (not graphing); some available here
• Observations – Earth-Sun Scale Model Due TODAY 11:59pm Jan. 28
– Sunset – Part 1 Due Feb. 18 (10 pts)Take picture of sunset (~4pm) at a
place you can return for part 2
– Star Gazing (SG) Due May 12 (20 pts) Go star gazing & write report
– Moon Phases Start Jan. 23; Due Mar. 5 (10 pts) Observe 4 phases &
record in table
– NEW: Planetarium (10 pts) See Calendar info about Field Trip on Feb. 4:
Bus from college at 8:15am and returns by 10:30am.
• You can watch Crash Course in Astronomy #3 & #5 to review
• Grades updated weekly (check for mistakes)
Homework