Charles Hakes Fort Lewis College1. Charles Hakes Fort Lewis College2 Exploring the Heavens Lunar Phases Eclipses History.

Charles HakesFort Lewis College 1

Exploring the Heavens

Lunar Phases

Eclipses

History

Outline

Notes Review Lunar Phases; Eclipses (0.3) History (1.1,1.2)

Lab Notes

• No in-class lab this week.• Telescope intro or resources part• Be thinking about those “report” labs.

Your Folder• Full name on the tab• BIG name on the front• Major on upper right• Class on lower left• A comment about yourself on the lower right• Inside - your most recent, or current, math class

(subject, course number, and year taken.)• Include your daily three minute papers! You can

reuse pages, just add the date.• Say something specific.

Review

• What was the most important thing you learned?• The smaller the parallax shift of an

object the further away the object is.• There are 2 radians in a circle.

Radians

• Not just an extra button on your calculator• 2 radians in a circle• Conversion formula

2 rad = 360°

• Conversion practice page on-line!

Small Angle Approximation

• Angle must be in radians• Angle must be small

• (opposite << adjacent)

• Then: sin() tan()

• For small angles in radians:

angle = baseline/distance

• For small angles in radians:

angle = baseline/distance

distance = baseline/angle

baseline = angle*distance

You see your friend in the distance and measure that they “subtend” 1 degree.

How many radians is that?

B) 1.6

C) .034

D) .017

E) .012

You know your friend is 1.6m tall, and that they “subtend” 0.017 radians.

How many far away are they?

A) 94m

B) 0.27m

C) 163m

D) 57m

E) 106m

Lunar Phases

Figure 1.1Lunar Phases

Which lunar phase rises at Sunset?

A) New.

B) First quarter.

C) Full.

D) Third quarter.

Which lunar phase rises at Sunset?

A) New.

B) First quarter.

C) Full.

D) Third quarter.

Vocabulary

• phases• new moon• first quarter• full moon• third quarter• crescent moon• gibbous• waxing• waning

Which lunar phase is overhead at sunset?

A) New.

B) First quarter.

C) Full.

D) Third quarter.

Which lunar phase is overhead at sunset?

A) New.

B) First quarter.

C) Full.

D) Third quarter.

Figure 1.1Lunar Phases

Eclipses

• Earth-Moon model

Figure 1.2Lunar Eclipse

Figure 1.3Solar Eclipse

Figure 1.4Solar Eclipse Types

Figure 1.5Eclipse Geometry

Figure 1.6Eclipse Tracks

Discovery 1-1bThe Scientific Method

Review

• The tilt of the ecliptic is 23.5°.• The tilt of the Moon’s orbit compared to the

ecliptic is 5.2°• The tilt is always 5.2°, however, the orbit

precesses (wobbles). Cycle is ~18.6 years.

Where does the full moon rise on June 21?

A) North of east (by more than 5°)

B) Within 5.2° of due east

C) South of east (by more than 5°)

D) Not enough information

Where does the full moon rise on June 21?

A) North of east (by more than 5°)

B) Within 5.2° of due east

C) South of east (by more than 5°)

D) Not enough information

Discussion

• Does the full moon get higher in the sky during summer or winter?

• The tilt of the Moon’s orbit compared to the ecliptic is 5.2°

• How high in the sky does the moon ever get?

• Where on the horizon would it rise then?

Chapter 1

Planets

• There are five “wanderers” in the sky.• Two are morning/evening stars

• Mercury• Morning or evening star.• Always close to the sun• Very quickly in and out of sight.

• Venus• Morning or evening star.• Brightest object next to the Sun and the Moon.• Can see it in broad daylight.

Planets

• Three are seen any time of night.• Brightest during retrograde (westward) motion

• Mars• Very red• Seen about every two years

• Jupiter• Brightest object next to Venus• Seen about every year(+)

• Saturn• Brighter than most stars• Seen about every year(+)

Figure 1.7Planetary Motions

Geocentric Universe

• Must explain both motion and brightness.• Epicycles used to explain motion and

brightness.• Deferent is the larger circle on which the

epicycle moves.• Ptolomy (~A.D. 140) constructed the best

of the geocentric models.• Eventually had to add epicycles onto the

epicycles.

Figure 1.8Geocentric Model

Figure 1.9Ptolemy’s Model

Figure 1.10Nicholas Copernicus (1473-1543)

Helioentric Universe

• Sun centered model.• The Copernican Revolution.• Much simpler (recall Occam’s razor).• But no more accurate.• Epicycles still needed to explain all

motion.• Retrograde motion is just from

perspective.

Figure 1.11Retrograde Motion

Figure 1.12Galileo Galilei (1564-1642)

Galileo’s Observations

• First to use a telescope to look at objects in the sky.• Moon mountains, craters.• Sunspots.• Jupiter’s moons.• Venus phases.

• Supported the view that the Earth was not the center of things.

Figure 1.13Galilean Moons

Figure 1.14aVenus Phases

Figure 1.14bVenus Phases

Summary

• Simpler models are better.• The Earth is not the center of things.

Review

• What was the most important thing you learned?• The further north you go, the lower the sun

gets. The opposite is true for the north star.• The sun is always higher in Durango than GJ (Grand Junction) at noon.

• It’s a lot easier to find out the answer the (PRS) questions when you discuss it thoroughly with your classmates.

Review

• What questions do you still have about today?• If you did the Durango/Grand Junction thing in

the tropics, would the results vary?• Yes, because the sun could be either North or South

of your position.

How high does the sun ever get in the Durango (37° N latitude) sky?

A) 37° above the Southern horizon

B) 53° above the Southern horizon

C) 76.5° above the Southern horizon

D) 90° straight up

How high does the sun ever get in the Durango (37° N latitude) sky?

A) 37° above the Southern horizon

B) 53° above the Southern horizon

C) 76.5° above the Southern horizon

D) 90° straight up

Figure P.11Parallax

Distances to Stars

• The biggest baseline is the best.• Use the diameter of the Earth’s orbit.

(distance = baseline/angle)• A Parsec is the distance of an object when

the observed parallax shift is one arc second when the baseline is one average radius of the Earth’s orbit (1 Astronomical Unit = 1 AU).

1 pc = 3.09x1013km = 3.3ly

Figure 10.1Stellar Parallax

You observe identical twins in the distance and measure their angular height. Joe appears 0.8 degrees tall and Bob appears 0.3 degrees tall.

A) Joe is a little farther away than Bob

B) Joe is more than twice as far away as Bob

C) Bob is a little farther away than Joe

D) Bob is more than twice as far away as Joe

E) Not enough information

You observe identical twins in the distance and measure their angular height. Joe appears 0.8 degrees tall and Bob appears 0.3 degrees tall.

A) Joe is a little farther away than Bob

B) Joe is more than twice as far away as Bob

C) Bob is a little farther away than Joe

D) Bob is more than twice as far away as Joe

E) Not enough information

Three Minute Paper

• Write 1-3 sentences.• What was the most important thing

you learned today?• What questions do you still have

about today’s topics?

Charles Hakes Fort Lewis College1. Charles Hakes Fort Lewis College2 Exploring the Heavens Lunar Phases Eclipses History.

small angle approximationangle

calculator2p radians

class lab

reviewthe tilt

lab notesno

lower rightinside

moons orbit

math class subject

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