1. Earth, Moon, and Sun

2. Gravity and Motion
Isaac Newton was the first scientist to explain what keeps the Earth and Moon in orbit
Force – a push or a pull
There is a force acting between the Earth and the moon that keeps them in orbit

3. Gravity Gravity attracts all objects toward each other
Measured in Newtons (N)
The Law of Universal Gravitation – every object in the universe attracts every other object
The strength of gravity depends on
Mass of each object
Distance between each object

4. gravity

5. Gravity, Mass, and Weight
Mass is the amount of matter in an object
Weight depends on the location of the object. The less gravity, the less the object weighs
Mass does not change, but weight does

6. Gravity and weight Planet Weight Earth 70 lbs Moon 12 lbs Mars 26 lbs
If an 11 year old boy weighs 70 lbs on Earth, how much will he weigh on other planets or the moon?
Planet
Weight
Earth
70 lbs
Moon
12 lbs
Mars
26 lbs
Jupiter
177 lbs
Pluto
5 lbs

7. Gravity and distance
The strength of gravity is affected by the distance between two objects as well as their masses
The force of gravity decreases as the distance between the objects increase

8. Inertia
Inertia is the tendency of an object to resist a change in motion
Newton’s 1st Law of Motion says “an object at rest will remain at rest, and an object in motion will remain in motion unless acted on by another force”

9. Inertia

10. Inertia

11. Earth in space

12. Astronomy
Astronomy is the study of the moon, stars, and other objects in space
Ancient Egyptians were among the first to study the stars
To recognize patterns in the location of stars during certain times of the year

13. How earth moves Earth moves through space in two ways Rotation
Revolution
Rotation is the spinning of the Earth on its axis
Causes Day and Night
Takes 24 hours to make one rotation
Revolution the movement of one object around another
Earth revolves around the sun
Moon revolves around Earth
Takes days to make one orbit
The orbit is not circular, but elliptical

14. How Earth Moves Earth’s rotation causes day and night
Earth rotates from west to east
The sun appears to move across the sky, but its not really moving
It takes Earth about 24 hours to rotate once completely on its axis.

15. How Earth Moves

16. How Earth moves
A calendar is a system of organizing time. For each year, the calendar includes:
Beginning-Jan. 1st
Length-365 days
Divisions-months
Egyptians created one of the first calendars based on the lunar “moonth” (where we get the name “month”)
The Romans adjusted the calendar to include Leap Year (to make-up for the extra .25 days it takes the Earth to orbit)

17. Seasons
Most place on Earth have four distinct seasons: winter, spring, summer, fall
Sunlight hits the Earth
Directly at the equator (warmer climate)
At an angle at the poles (much cooler climate)
Earth has seasons because its axis is titled as it revolves around the sun
23.50 angle of the Earth’s tilt
The change in seasons is NOT caused by changes in the Earth’s distance from the sun

21. June and december
In June, the north end of the Earth is tilted toward the sun
Northern Hemisphere – the days are longer and temperature is warmer
Southern Hemisphere – the days are shorter and temperature is cooler
In December, the south end of the Earth is tilted toward the sun
Northern Hemisphere – the days are shorter and temperature is cooler
Southern Hemisphere – the days are longer and temperature is warmer

22. Solstices
A solstice occurs when the sun is farthest from the north pole or the south pole.
Northern Hemisphere
June 21st is the Summer Solstice – the sun is closest to the North Pole
It’s the longest day of the year (most hours of daylight – still 24 hours)
December 21st is the Winter Solstice – the sun is closest to the South Pole
It’s the shortest day of the year (fewest hours of daylight – still 24 hours)

25. Equinoxes
An Equinox is when the Earth is not tilted toward or away from the sun and the NOON sun is directly over the equator
There is equal amounts of sunlight – 12 hours of day, 12 hours of night (equal – equinox)
Occurs twice a year: March 21st (Spring) and September 21st (Fall)