Astronomy 1 Fall 2014 Lecture 2; October 7, 2014 UCSB Astro 1 -
Martin Set your alarm clock for 3am to see tonights eclipse!
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Previously on Astro-1 Goal 1 The big picture The Universe is
huge; we will make a Grand Tour Goal 2 The scientific method
Demarcation: what is science? Falsification: how do you test
scientific theories? Corroboration: what is a good scientific
theory? Goal 3 Learning scientific language Science terms have very
precise definitions, with sometimes somewhat different meaning than
in the current language (e.g., Powers of ten; Units;Small Angle
Formula) UCSB Astro 1 - Martin2
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Today on Astro-1 Constellations & Celestial Sphere Seasons
The moons orbit Lunar eclipses Solar eclipses Ancient studies of
moon and suns orbit UCSB Astro 1 - Martin3
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The Night Sky UCSB Astro 1 - Martin4
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The sky is divided into 88 constellations, but the stars are at
different distances UCSB Astro 1 - Martin5
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The diurnal (daily) motion of the stars. UCSB Astro 1 -
Martin8
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The diurnal (daily) motion of the stars. UCSB Astro 1 -
Martin9
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The night sky changes during the year How fast does the
position of the Earth move around the sun every month? UCSB Astro 1
- Martin10
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The imaginary celestial sphere. The celestial equator and poles
are projections of the Earths axis of rotation out into space. UCSB
Astro 1 - Martin11
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Seasons UCSB Astro 1 - Martin13
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Ecliptic plane: the plane in which the Earth moves around the
Sun. UCSB Astro 1 - Martin16
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Ecliptic plane and the ecliptic: just a matter of perspective
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Midight Sun from Arctic Circle UCSB Astro 1 - Martin 22 What
direction is the photographer facing? A.North B.South C.East D.West
E.None of the above. This photograph was photoshopped.
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The Moons Orbit UCSB Astro 1 - Martin23
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This picture of the Earth and the Moon was taken in 1992 by the
Galileo spacecraft on its way toward Jupiter. UCSB Astro 1 -
Martin24
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What you see from earth UCSB Astro 1 - Martin25
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When do you see the moon in the morning sky? UCSB Astro 1 -
Martin26
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Sidereal month: the time the Moon takes to complete one full
revolution around the Earth with respect to the background stars:
27.32 days Synodic (lunar) month: Time from one new moon to the
next: 29 days. UCSB Astro 1 - Martin28
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Why dont we have eclipses every month? UCSB Astro 1 -
Martin29
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Lunar eclipse: Moon is in the shadow of the Earth UCSB Astro 1
- Martin31
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Lunar eclipse: three types UCSB Astro 1 - Martin32
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The Moon moving through the Earths umbra over 3 hours. UCSB
Astro 1 - Martin33
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On average, two or three lunar eclipses occur in a year. Of all
lunar eclipses, roughly one-third are total, one-third are partial,
and one-third are penumbral.
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Tonights Eclipse UCSB Astro 1 - Martin35
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How did ancient astronomers discover that the Earth is round?
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Solar eclipse UCSB Astro 1 - Martin37
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A total solar eclipse. The moon passes in front of the sun.
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During a total solar eclipse, the tip of the Moons shadow
traces an eclipse path across the Earths surface. People within the
eclipse path see a total solar eclipse as the tip moves over them.
Anyone within the penumbra sees only a partial eclipse. Photo from
Russian space station Mir (of same eclipse in previous 2 slides)!
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Annular solar eclipse. UCSB Astro 1 - Martin43
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There are at least two, but never more than five solar eclipses
each year.
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Eratostheness determined the diameter of the Earth around 200
B.C.! Distance from Alexandria to Syene was said to be about 5000
stades, so Earths circumference was computed to be 50 5000 =
250,000 stades UCSB Astro 1 - Martin46
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Aristarchus determined distances to sun and moon, and
determined sizes of moon and sun relative to Earth around 280 B.C.!
He got the answer wrong because of poor measurements, but had the
right technique. UCSB Astro 1 - Martin47
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Summary The night sky Seasons Why is it colder in winter? Lunar
Phases: How do they arise? Length of the Month: How long does it
take for the moon to go around the Earth? The Moons Orbit: Why dont
we have lunar eclipses every month? Solar eclipses What kind of
solar eclipses are there? When do they happen? UCSB Astro 1 -
Martin49
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Homework Due 10/13/14 On your own: answer all the review
questions in chapter 2-3. To TAs: answer questions 2.40, 2.46,
3.31, 3.43 UCSB Astro 1 - Martin50
