BellworkBellworkTrue or False:True or False:

1. Mirrors are used in some telescopes.1. Mirrors are used in some telescopes.

2. Telescopes are often located in humid 2. Telescopes are often located in humid environments because water vapor in the environments because water vapor in the air enhances visibility of stars.air enhances visibility of stars.

BellworkBellworkList the planets in order by the time it List the planets in order by the time it

takes to orbit the sun from fastest to takes to orbit the sun from fastest to slowest.slowest.

If the semimajor axis of Earth’s orbit is 150 If the semimajor axis of Earth’s orbit is 150 million Km, what is the major axis? (use million Km, what is the major axis? (use pg. 81 for help)pg. 81 for help)

What 2 properties affect the force of What 2 properties affect the force of gravity?gravity?

Astronomy Astronomy

BellworkBellworkWhat is astronomy?What is astronomy?

ObjectiveObjective: Students will : Students will describe the difference between describe the difference between rotation and revolution in written rotation and revolution in written

notes.notes.

Astronomy is…Astronomy is…

the study of the universe to include the study of the universe to include moons, planets, stars, and other objects in moons, planets, stars, and other objects in spacespace

Beginnings of AstronomyBeginnings of Astronomy

Have you ever asked yourself?Have you ever asked yourself?

Why do the planets revolve around the Why do the planets revolve around the sun?sun?

Why don’t they fly off into space?Why don’t they fly off into space?

Does something hold them in their paths?Does something hold them in their paths?

This man This man has the has the answers

answers

Can you distinguish the Can you distinguish the difference between difference between rotation rotation

and and revolutionrevolution??

Difference between rotation and Difference between rotation and revolution.revolution.

Rotation Rotation When an object in When an object in

space spins on it’s space spins on it’s axisaxis

Earth’s rotation on it’s Earth’s rotation on it’s axis causes day and axis causes day and nightnight

RevolutionRevolution The movement of one The movement of one

object around anotherobject around another Earth’s revolution Earth’s revolution

around the sun is around the sun is called a year.called a year.

Time Measurements

DAY (rotation)

– time it takes for a planet to rotate once around its own axis.

Earth – about every 24 hours

(23 hrs 56 min)

Sun

EPlanet

YEAR (revolution)

– time it takes for a planet to orbit once around the sun.

Earth – every 365.26 days

Why is there an extra day in Why is there an extra day in February every fourth year?February every fourth year?

Earth’s orbit takes 365 ¼ days. To Earth’s orbit takes 365 ¼ days. To account for the ¼ day we add an extra day account for the ¼ day we add an extra day every fourth year. We call that year leap every fourth year. We call that year leap year.year.

Why do we have seasons?Why do we have seasons?

Earth has seasons because its axis it tilted Earth has seasons because its axis it tilted as it moves around the sun.as it moves around the sun.

Seasons – The tilt of the Earth’s axis causes the northern & southern

hemispheres to get different amounts of solar radiation causing the different weather.

Solstice and EquinoxSolstice and Equinox

SolsticeSolstice Two days of the year Two days of the year

where the noon sun is where the noon sun is overhead at either overhead at either 23.5 degrees south or 23.5 degrees south or 23.5 degrees north.23.5 degrees north.

EquinoxEquinox Two days of the year Two days of the year

where neither where neither hemisphere is tilted hemisphere is tilted toward or away from toward or away from the sun the sun

Equinox means “equal Equinox means “equal night” night”

The amount of sunlight hitting different parts of the Earth changes as the Earth moves around the Sun over a year.

Sep 21, 2005

Dec 20, 2005

Mar 20, 2006

Jun 21, 2006

Sep 23, 2006

Summer SOLSTICE

the one day of the year when the sunlight time is longest.

Sep 21, 2005

Dec 20, 2005

Mar 20, 2006

Jun 21, 2006

Sep 23, 2006

Winter SOLSTICE

the one day of the year when the sunlight time is shortest.

Sep 21, 2005

Dec 20, 2005

Mar 20, 2006

Jun 21, 2006

Sep 23, 2006

Spring EQUINOX

the one day between winter and summer when the sunlight time and night time are of equal length.

Sep 21, 2005

Dec 20, 2005

Mar 20, 2006

Jun 21, 2006

Sep 23, 2006

Autumn EQUINOX

the one day between summer and winter when the sunlight time and night time are of equal length.

Sep 21, 2005

Dec 20, 2005

Mar 20, 2006

Jun 21, 2006

Sep 23, 2006

Chapter 1 Section 1 ReviewChapter 1 Section 1 Review

Why does Earth have day and night?Why does Earth have day and night?Why does Earth have seasons?Why does Earth have seasons?What is the difference between rotation What is the difference between rotation

and revolution?and revolution?What is leap year?What is leap year?

What is an What is an astronomical astronomical unit?unit?

AU – the distance AU – the distance from the earth to from the earth to the sun. Approx. the sun. Approx. 150 million 150 million kilometerskilometers

Kepler’s 3 LawsKepler’s 3 Laws

What are What are

Kepler’s Kepler’s laws of laws of motion?motion?

- The first law states that The first law states that orbits are elliptical.orbits are elliptical.

- An ellipse is a closed An ellipse is a closed curve in which the sum curve in which the sum of the distances from of the distances from the edge of the curve to the edge of the curve to two points inside the two points inside the ellipse is always the ellipse is always the same.same.

What are What are

Kepler’s Kepler’s laws of laws of motion?motion?

- The second says that The second says that planets move faster planets move faster when they are closer to when they are closer to the sun and slower the the sun and slower the farther away they are.farther away they are.

- Mercury, the innermost planet, takes only 88 days to orbit the Sun but the outermost planet (Pluto) requires 248 years to do the same

What are What are

Kepler’s Kepler’s laws of laws of motion?motion?

- The third explains the The third explains the relationship between relationship between the period of revolution the period of revolution and the semimajor axis and the semimajor axis of the elliptical orbit. of the elliptical orbit.

- Planets further from the sun, such as Saturn, take longer to orbit the sun.

How does the How does the

Law of UniversalLaw of Universal

Gravitation explainGravitation explain

how the objects in thehow the objects in the

solar system revolvesolar system revolve

around the Sun?around the Sun?

-Newton explained that -Newton explained that the force of gravity on the force of gravity on an object in the solar an object in the solar system depends on system depends on its mass and distance its mass and distance from the sun. from the sun.

-This force along with -This force along with the forward motion of the forward motion of the object keeps it in the object keeps it in an elliptical orbit an elliptical orbit around the sun.around the sun.

Newton’s law of universal gravitation- The force Newton’s law of universal gravitation- The force of gravity depends on the product of the masses of gravity depends on the product of the masses of the object divided by the square of the of the object divided by the square of the distance between the objects. distance between the objects.

BellworkBellwork

List the planets in order by the time it List the planets in order by the time it takes to orbit the sun from fastest to takes to orbit the sun from fastest to slowest.slowest.

If the semimajor axis of Earth’s orbit is 150 If the semimajor axis of Earth’s orbit is 150 million Km, what is the major axis? (use million Km, what is the major axis? (use pg. 81 for help)pg. 81 for help)

BellworkBellwork

List the planets in order by the time it List the planets in order by the time it takes to orbit the sun from fastest to takes to orbit the sun from fastest to slowest.slowest.

If the semimajor axis of Earth’s orbit is 150 If the semimajor axis of Earth’s orbit is 150 million Km, what is the major axis? (use million Km, what is the major axis? (use pg. 81 for help)pg. 81 for help)

What 2 properties affect the force of What 2 properties affect the force of gravity?gravity?