Science Chapter 11 Changing Seasons Flashcards

Seasons and Their Causes

• Earth’s axial tilt is responsible for the changing seasons.
• Revolution refers to Earth's yearlong orbit around the Sun.
• Earth's orbit is elliptical, meaning it is an elongated close curve.

Proximity to the Sun

• Earth is closest to the Sun in January.
• Earth is farthest from the Sun in July.

Sunlight Distribution

• The hemisphere tilted toward the Sun receives more hours of sunlight compared to the opposing hemisphere.
• The tilt also affects how solar radiation strikes different angles on Earth.

Solstices and Equinoxes

• A solstice is the day when the Sun reaches its maximum distance north or south of the equator.
• Summer solstice in the Northern Hemisphere occurs around June 21 or 22, marking the longest hours of daylight.
• Winter solstice occurs around December 21 or 22, indicating the least amount of sunlight received.

Equinox Definition

• An equinox occurs when the Sun is directly above Earth’s equator, leading to equal day and night lengths.
• There are two equinoxes each year: spring and fall.

Spring and Fall Equinox

• Spring equinox happens on March 20 or 21 and signals the start of spring.
• Fall equinox takes place on September 22 or 23, marking the beginning of fall; the seasons are reversed in the Southern Hemisphere.

June Solstice Details

• June 21 marks the Northern Hemisphere's tilt towards the Sun, resulting in the longest day and shortest night—signifying the arrival of summer.
• After this date, daylight hours begin to decrease.

September Equinox Details

• September 23 represents a day when neither hemisphere tilts towards the Sun, leading to equal lengths of day and night.
• This equinox marks the onset of fall in the Northern Hemisphere.

December Solstice Details

• December 21 indicates the Northern Hemisphere's maximum tilt away from the Sun, producing the shortest day and longest night—ushering in winter.
• Following this, daylight hours start to increase.

Vernal Equinox Details

• March 21 is the vernal equinox, where both hemispheres receive equal day and night lengths.
• This date signifies the beginning of spring, after which days become longer than nights.