Earth, Moon, and Sun

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

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

gravity

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

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

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

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”

Inertia

Inertia

Earth in space

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

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 365.25 days to make one orbit The orbit is not circular, but elliptical

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.

How Earth Moves

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)

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

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

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)

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)