Chapter2 1

Chapter 2Discovering the Universe for Yourself: 

Chapter 2 Discovering the Universe for Yourself

Star Patterns…: 

Star Patterns… From the earliest days, our ancestors sought to find rhyme and reason for the stars in the heavens and their perceived motions. Religion and superstition defined how Man looked at the stars, because there was no way to formulate a theory and then test it. The tools didn’t exist.

Constellations make locating stars easy: 

Constellations make locating stars easy

Use the Big Dipper in the northern sky as a way to find other groups of stars: 

Use the Big Dipper in the northern sky as a way to find other groups of stars

Use the winter triangle to find southern constellations during winter evenings: 

Use the winter triangle to find southern constellations during winter evenings

Use the Summer Triangle to find southern constellations during summer evenings: 

Use the Summer Triangle to find southern constellations during summer evenings

Angular distances between stars in the sky are measured in degrees: 

Angular distances between stars in the sky are measured in degrees

Angular distances between stars in the sky are measured in degrees: 

Angular distances between stars in the sky are measured in degrees

An imaginary Celestial Sphere surrounding Earth aids in navigating the sky: 

An imaginary Celestial Sphere surrounding Earth aids in navigating the sky

Elements of the equatorial coordinate system on the celestial sphere: 

Elements of the equatorial coordinate system on the celestial sphere Vernal Equinox: The position of the Sun on the first day of spring Right Ascension: How far east of the Vernal Equinox an object is located Celestial Equator: The line separating the celestial sphere into northern and southern halves. Declination: How far above or below the celestial equator an object is located.

Earth’s rotation causes the Sun and stars to appear to move: 

Earth’s rotation causes the Sun and stars to appear to move

Motion of Stars and Planets: 

Motion of Stars and Planets Did you know the stars rise in the East and set in the West, like the Sun? Think about this as we introduce the Celestial Sphere. What do you think happens to the stars during the day?

Motion of Stars at the North Pole: 

Motion of Stars at the North Pole

Motion of Stars at the Equator: 

Motion of Stars at the Equator

What about the Sun? It seems to move across the celestial sphere on a path called the ecliptic.: 

What about the Sun? It seems to move across the celestial sphere on a path called the ecliptic.

Position of the “noon-time” Sun when photographed every two weeks over a year: 

Position of the “noon-time” Sun when photographed every two weeks over a year

The “altitude” of the Sun impacts how much energy is received on Earth resulting in seasons.: 

The “altitude” of the Sun impacts how much energy is received on Earth resulting in seasons.

The seasons are caused by the tilt of the Earth’s axis of rotation: 

The seasons are caused by the tilt of the Earth’s axis of rotation

In other words ...: 

In other words ... The Earth’s rotation on its axis determines the length of the day The Earth’s orbit around the Sun (revolution) determines the length of the year The Earth’s tilt with respect to the ecliptic causes the seasons.

Precession is a slow, circular motion of the Earth’s axis of rotation: 

Precession is a slow, circular motion of the Earth’s axis of rotation

Precession causes the position of the NCP to change over a period of 26,000 years. : 

Precession causes the position of the NCP to change over a period of 26,000 years.

The changing phases of the Moon originally inspired the concept of the month: 

The changing phases of the Moon originally inspired the concept of the month

Moon Phase Names: 

Moon Phase Names New Moon Waxing Crescent First Quarter Waxing Gibbous Full Moon Full Moon Waning Gibbous Third Quarter Waning Crescent New Moon

Slide27: 

Although the Moon is always lit from the Sun, we see different amounts of the lit portion from Earth depending on where the Moon is located in its month-long orbit.

Slide28: 

How long does it take to go from new moon to new moon? 27.3 days 29.5 days How long does it take the Moon to orbit Earth?

Eclipses occur only when the Moon crosses the ecliptic during the new or full phase: 

Eclipses occur only when the Moon crosses the ecliptic during the new or full phase

Slide30: 

Types of Lunar Eclipses total eclipse penumbral eclipse partial eclipse

Slide31: 

Mechanics of a Solar Eclipse

Solar Eclipse: 

Solar Eclipse