1. Table of Contents Earth in Space Gravity and Motion
Phases, Eclipses, and Tides
Earth’s Moon

2. What is Astronomy?
Astronomy – the study of the moon, stars, and other objects in space

3. Where did it originate?
One of the first theories about the solar system stated that the Earth, Sun, and Moon are all within a “celestial sphere” which has holes that allows light to come through from the heavens (stars).

4. Earth in Space
For centuries astronomers have been studying the movements of the sun and the moon across the Earth
Many astronomers believed that the Earth stood still while the sun moved across it.

5. How Earth Moves - Earth in Space
Earth moves through space in two major ways: rotation and revolution.

6. Earth in Space Rotation – the spinning of the Earth on its axis
Axis – the imaginary line that passes through the center of the Earth (on a 23.5º tilt)
Revolution – the movement of one object around another (ie. the Earth around the sun)
One complete revolution takes 1 year (365 1/4 days)

7. Earth in Space
Calendars – are systems of organizing time and defines the beginning, length, and divisions of a year.
They have been used for centuries.
The earth follows an orbit (path)
Misconception!! “The Earth’s orbit is NOT round but slightly elliptical.”

8. Sunlight Striking Earth’s Surface
- Earth in Space
Sunlight Striking Earth’s Surface
Near the equator, sunlight strikes Earth’s surface more directly and is less spread out than near the poles.

9. The Seasons on the Earth
Because of the way the sun’s rays hit the Earth, temperatures tend to be warmer in the tropics and cooler in the polar regions

10. The Seasons on the Earth
There are 4 basic seasons on the Earth between the tropic and polar regions
They include : Spring, Summer, Fall, and Winter
The seasons occur because the Earth is tilted 23.5°on an axis
As the Earth revolves around the sun certain parts of the Earth receive more sunlight during certain times of the year

11. The Seasons on the Earth
When it is summer in the Northern Hemisphere it is winter in the Southern Hemisphere and visa versa.
In the Northern Hemisphere (where we live):
March = Spring Equinox
June = Summer Solstice
September = Fall Equinox
December = Winter Solstice (North axis is pointed away from the sun)

12. Seasons on Earth - Earth in Space
Earth has seasons because it is tilted as it revolves around the sun.

13. Seasons on Earth - Earth in Space
The height of the sun above the horizon varies with the season.

14. The Seasons on the Earth
In June the north axis is pointed towards the sun
The noon sun is high in the sky and there are more daylight hours
In December the north axis is pointed away from the sun
The noon sun is lower in the sky and there are less daytime hours

15. Graphic Organizer Earth Around the sun On its axis Night and day Years
rotates
revolves
Around the sun
On its axis
causing
causing
Night and day
Years

16. The Seasons on the Earth
A solstice is when the sun is either the furthest north or south of the equator. They occur June 21 (furthest north) and December 21 (furthest south)
An equinox is when the noon sun is directly overhead at the equator. They occur March 21 and September 22.
The word equinox means “equal night” because there are roughly 12 hrs of both day and night throughout the world on those dates.

17. Seasons Activity - Earth in Space
Click the Active Art button to open a browser window and access Active Art about the seasons.

18. Gravity and Motion
In the 17th Century Isaac Newton studied various forces (a push or pull on an object)
One of these forces was gravity which is the force that attracts all objects toward each other. Newton called this the law of universal gravitation.

19. - Gravity and Motion
Gravity
The strength of the force of gravity between two objects depends on two factors: the masses of the objects and the distance between them.

20. Mass is the amount of matter in an object
Mass vs. Weight
Mass is the amount of matter in an object
Weight is the force of gravity pulling on an object
Unlike mass that never changes an object’s weight can change depending on location.

21. Gravity Versus Distance
- Gravity and Motion
Gravity Versus Distance
As a rocket leaves a planet’s surface, the force of gravity between the rocket and the planet changes. Use the graph to answer the following questions.

22. Gravity Versus Distance
- Gravity and Motion
Gravity Versus Distance
Reading Graphs:
What two variables are being graphed? In what units is each variable measured?
Force of gravity on the rocket in millions of newtons and distance from the planet’s center in planetary radii

23. Gravity Versus Distance
- Gravity and Motion
Gravity Versus Distance
Reading Graphs:
What is the force of gravity on the rocket at the planet’s surface?
Four million newtons

24. Gravity Versus Distance
- Gravity and Motion
Gravity Versus Distance
Reading Graphs:
What is the force of gravity on the rocket at a distance of two units (twice the planet’s radius from its center)?
One million newtons

25. Gravity Versus Distance
- Gravity and Motion
Gravity Versus Distance
Making Generalizations:
In general, how does the force of gravity pulling on the rocket change as the distance between it and the planet increases?
It decreases.

26. Gravity and Inertia - Gravity and Motion
Newton concluded that two factors– gravity and inertia –combine to keep the moon in orbit around Earth.

27. Gravity and Motion
Inertia is the tendency of an object to resist a change in motion
Ex: When a car stops suddenly the passengers continue to move forward
Inertia is what keeps the Earth, moon, sun, and other planets from crashing into each other.
Newton concluded that both gravity and inertia help keep the Earth in orbit around the sun and the moon in orbit around the Earth. He called this orbital motion.

28. Click the SciLinks button for links on gravity.
- Gravity and Motion
Links on Gravity
Click the SciLinks button for links on gravity.

29. Motions of the Moon - Phases, Eclipses, and Tides
The changing relative positions of the moon, Earth, and sun cause the phases of the moon, eclipses, and tides.
It takes the moon 27.3 days to revolve around the Earth and 27.3 days to make one complete rotation….This means that we are always facing the same side of the moon (explains the “man in the moon” expression)

31. Phases, Eclipses, and Tides
The moon appears bright because it reflects the sun’s light
As the moon revolves around the Earth and the Earth revolves around the sun it creates different phases (shapes)

32. Phases of the Moon - Phases, Eclipses, and Tides
The phase of moon you see depends on how much of the sunlit side of the moon faces Earth.

33. Phases of the Moon
New Moon – the moon is between the sun and the Earth and not visible to us
Waxing – when the visible portion of the moon is increasing
Waxing-crescent – when the first sliver of the moon becomes visible after the new moon
First quarter – follows the waxing-crescent when half of the moon facing the earth becomes visible

34. Phases of the Moon
Waxing-gibbous – follows the first quarter when slightly more than half of the moon facing the Earth becomes visible
Full moon – the Earth is between the sun and the moon and the entire side of the moon facing the Earth is visible
Waning – when the visible portion of the moon is decreasing

35. Phases of the Moon
Waning-gibbous - following the full moon when the visible part of the moon facing Earth is slightly larger than half
Third(Last) quarter - follows the waning-gibbous when half of the moon facing the earth becomes visible
Waning-crescent - when the last sliver of the moon becomes visible before the new moon

36. Phases of the Moon
The period from one new moon to the next is 29.5 days.
“Once in a blue moon….”
A blue moon occurs when there are two full moons in the same month….does not happen very often.

38. Moon Phases and Eclipses Activity
- Phases, Eclipses, and Tides
Moon Phases and Eclipses Activity
Click the Active Art button to open a browser window and access Active Art about moon phases and eclipses.

39. The Moon’s Orbit - Phases, Eclipses, and Tides
The moon’s orbit is tilted about 5 degrees relative to Earth’s orbit around the sun.

40. - Phases, Eclipses, and Tides
Solar Eclipse
A solar eclipse occurs when the moon passes directly between Earth and the sun, blocking sunlight from parts of Earth.

41. Solar Eclipses
Total Solar Eclipse – darkest part of the moon’s shadow (the umbra) blocks out the sunlight
Partial Solar Eclipse – the lighter part of the moon’s shadow (the penumbra) blocks out the sunlight

42. - Phases, Eclipses, and Tides
Lunar Eclipse
During a lunar eclipse, Earth blocks sunlight from reaching the moon.

43. Lunar Eclipses
Total Lunar Eclipse – darkest part of the Earth’s shadow (the umbra) blocks out the reflected light of the moon
Partial Lunar Eclipse – the moon earth and sun aren’t completely in line causing the Earth’s shadow to cover only part of the moon

44. - Phases, Eclipses, and Tides
Tides occur mainly due to the difference in the force of gravity between the moon and different parts of Earth.

45. Spring and Neap Tides - Phases, Eclipses, and Tides
When Earth, the sun, and the moon are in a straight line, a spring tide occurs. When the moon is at a right angle to the sun, a neap tide occurs.

46. The Moon’s Surface - Earth’s Moon
Features on the moon’s surface include maria, craters, and highlands.
The dark, flat areas on the moon’s surface are called the maria.
The light-colored features that cover much of the moon’s surface are highlands.

47. The Moon’s Size - Earth’s Moon
The moon is 3,476 km in diameter, a little less than the distance across the contiguous Untied States.

48. The Origin of the Moon - Earth’s Moon
Scientists theorize that a planet-sized object collided with earth to form the moon.

49. Click the SciLinks button for links on Earth’s moon.

50. Comets
Comets – loose collections of ice, dust, and small rocky particles.
Have orbits that are usually very long, narrow ellipses.
Comets consist of three parts.
Nucleus – solid center
Coma – gas and dust surrounding the nucleus
Tail – gas, ice, and dust trailing behind

51. - Comets, Asteroids, and Meteors
Structure of a Comet
Most comets have two tails—a bluish gas tail and a white dust tail. The name comet means “long-haired star” in Greek

52. - Comets, Asteroids, and Meteors
Comet Orbits
Most comets revolve around the sun in very long, narrow orbits. Gas and dust tails form as the comet approaches the sun.

53. Asteroids Too small and numerous to be considered planets.
Asteroid – rocky objects revolving around the sun.
Too small and numerous to be considered planets.

54. Asteroids
Asteroid belt – region of the solar system between the orbits of Mars and Jupiter, where many asteroids are found.
Most are less than a kilometer, but some reach 300 kilometers in diameter.
Scientists believe a large asteroid struck the earth 65 million years ago, and it is probable that one will struck again in the future.

55. Meteoroids Meteoroid – a chunk of rock or dust in space
Meteor – a meteoroid that has entered the earth’s atmosphere and burns up.
Also known as a “shooting star”
Meteorite – a meteoroid that passes through the atmosphere and hits Earth’s surface.

56. Comparing and Contrasting
- Comets, Asteroids, and Meteors
Comparing and Contrasting
Comets, Asteroids, and Meteoroids
Feature
Feature
Comets
Comets
Asteroids
Asteroids
Meteoroids
Meteoroids
Kuiper belt and Oort cloud
Kuiper belt and Oort cloud
Between the orbits of Mars and Jupiter
Between the orbits of Mars and Jupiter
Origin
Origin
Comets or asteroids
Comets or asteroids
Excluding the tail, about the size of a mountain
Excluding the tail, about the size of a mountain
Typically less than 1 km; some are more than 300 km in diameter
Typically less than 1 km; some are more than 300 km in diameter
Smaller than comets or asteroids
Smaller than comets or asteroids
Size
Size
Ice, dust, small rocky particles
Ice, dust, small rocky particles
Composition
Composition
Rock
Rock
Rock or dust
Rock or dust