Why Do We Have Different Seasons? | California Academy of Sciences

California Academy of Sciences

28 Aug 201503:17

Summary

TLDRThe Earth's tilt and orbit around the Sun create seasonal changes, affecting both hemispheres differently. During winter in the northern hemisphere, the North Pole is tilted away from the Sun, resulting in cooler temperatures, short days, and long nights. As Earth orbits, spring brings equal day and night lengths, while summer sees the North Pole tilt towards the Sun, leading to warmer weather and longer daylight hours. This tilt also causes the opposite season in the southern hemisphere. Seasonal changes impact life on Earth, influencing primary producers like phytoplankton and forests, which respond to varying sunlight, affecting photosynthesis and the planet's carbon dioxide levels.

Takeaways

🌎 Earth's orbit around the Sun takes a full year, which is the basis for our calendar year.
🌐 Earth's axial tilt remains constant as it orbits the Sun, leading to seasonal changes.
❄️ In the northern hemisphere's winter, the North Pole is tilted away from the Sun, resulting in less direct sunlight and colder temperatures.
🌞 As Earth moves towards spring, the tilt neither faces directly towards nor away from the Sun, leading to more balanced day and night lengths.
🏞️ During summer in the northern hemisphere, the North Pole tilts towards the Sun, increasing direct sunlight and warmer temperatures.
🌡️ The angle and duration of sunlight exposure cause the seasonal temperature variations and affect the length of day and night.
🌏 The seasons are reversed in the southern hemisphere due to Earth's tilt, experiencing winter when the northern hemisphere has summer.
🌿 Primary producers, like plants and phytoplankton, depend on sunlight and respond to seasonal changes, affecting their photosynthetic activity.
🌱 Satellites measure the amount of carbon dioxide absorbed by primary producers, which is highest in regions with the most photosynthetic activity.
🌊 Ocean life, particularly phytoplankton, forms the base of the marine food web and is sensitive to seasonal changes, impacting the entire ecosystem.
🌳 On land, forests reflect the seasonal changes by turning green in spring and appearing darker in winter due to reduced photosynthesis.

Q & A

What causes the Earth to have different seasons throughout the year?
-The Earth's tilt on its axis and its orbit around the Sun cause the different seasons. As the Earth orbits, its tilt means different parts of the planet receive varying amounts of sunlight at different times of the year.
Why does the North Pole tip away from the Sun during winter in the northern hemisphere?
-During winter in the northern hemisphere, the North Pole tips away from the Sun because of Earth's axial tilt. This results in sunlight striking the northern hemisphere at a shallow angle for a shorter period of time.
How does the angle of sunlight affect the climate of the northern hemisphere during winter?
-The shallow angle at which sunlight strikes the northern hemisphere during winter results in cooler weather, shorter days, and longer nights.
What happens to the length of day and night as the Earth moves from winter to spring in the northern hemisphere?
-As the Earth moves from winter to spring in the northern hemisphere, the tilt of the Earth neither points towards nor away from the Sun, making day and night approximately equal in length.
Why are the days longer and warmer during summer in the northern hemisphere?
-During summer in the northern hemisphere, the North Pole tips towards the Sun, sunlight strikes more directly, and the Sun remains in the sky for a longer period, leading to warmer days.
How is the season in the southern hemisphere opposite to that of the northern hemisphere?
-Because of Earth's tilt, when it is summer in the northern hemisphere, it is winter in the southern hemisphere, and vice versa, due to the reversed sunlight exposure caused by the tilt.
How do primary producers, such as plants and phytoplankton, respond to seasonal changes?
-Primary producers depend on sunlight for photosynthesis and respond to the changes in seasons. They absorb more carbon dioxide and produce oxygen and natural sugars during periods of increased sunlight.
What role do phytoplankton play in the ocean's food web?
-Phytoplankton, as microscopic photosynthesizers, form the base of the ocean food web. Their productivity increases significantly during spring, affecting all ocean life.
How do forests on land reflect the changes in seasons?
-Forests on land grow green during spring, indicating increased photosynthesis, and turn dark during winter due to reduced photosynthetic activity, reflecting the seasonal changes.
How can the amount of carbon dioxide absorbed by primary producers be measured?
-The amount of carbon dioxide absorbed by primary producers can be measured using Earth orbiting satellites that monitor the changes in carbon dioxide levels.
What visual representation is used to show where primary producers are most active in absorbing carbon dioxide?
-Bright regions on a map indicate where primary producers are most active in absorbing carbon dioxide, turning light from the Sun into oxygen and natural sugars.

Outlines

00:00

🌐 Earth's Orbit and Seasons

This paragraph explains the Earth's orbit around the Sun and its axial tilt, which remain constant throughout the year. The tilt causes the Sun's light to hit the Earth at different angles, resulting in the four seasons. During winter in the northern hemisphere, the North Pole is tilted away from the Sun, leading to shallow sunlight angles, short days, and long nights. As Earth orbits towards spring, the tilt is neutral, making day and night equal in length. In summer, the North Pole tilts towards the Sun, increasing sunlight intensity and duration, leading to warmer temperatures. The reverse is true for the southern hemisphere, where summer corresponds to the northern hemisphere's winter. The paragraph also touches on how the Earth's tilt affects life, particularly primary producers like plants and phytoplankton, which respond to seasonal sunlight changes, influencing the amount of carbon dioxide they absorb and the subsequent impact on the planet's ecosystems.

Mindmap

Keywords

💡Earth's orbit

Earth's orbit refers to the path the planet takes around the Sun, which is a critical concept in the video as it explains the basis for the changing seasons. The Earth's orbit takes approximately one year to complete. The video script mentions that 'it takes a full year for our planet to complete its orbit,' illustrating the fundamental role this plays in the seasonal cycle.

💡Rotation

Rotation is the spinning of Earth on its axis, which is a daily occurrence and distinct from its orbital motion around the Sun. The video mentions that 'Earth also rotates like a slightly tilted spinning top,' emphasizing that this tilt is consistent throughout the year and contributes to the seasonal variations experienced on the planet.

💡Tilt

The tilt of Earth's axis is a key factor in the video's explanation of seasons. The Earth remains 'tilted in the same direction all year round,' which means that the angle at which sunlight strikes the planet's surface changes with the position in its orbit, leading to different intensities of sunlight and thus different seasons.

💡Seasons

Seasons are the result of Earth's axial tilt and its orbit around the Sun. The video script describes how 'the seasons are reversed' due to Earth's tilt, with winter in the northern hemisphere when it's summer in the southern hemisphere. This concept is central to understanding the environmental changes depicted in the video.

💡Sunlight

Sunlight is the source of energy for life on Earth and plays a crucial role in the video's discussion of seasons. The script explains how 'the sun's light shines differently on Earth at different times of the year,' affecting temperatures and the length of day and night, which in turn influences weather patterns and biological processes.

💡Primary producers

Primary producers, such as phytoplankton and plants, are organisms that convert sunlight into energy through photosynthesis. The video script notes their dependency on sunlight and how they 'respond to the changes in the seasons.' These organisms are highlighted as the base of various ecosystems and are integral to the Earth's carbon cycle.

💡Photosynthesis

Photosynthesis is the process by which primary producers convert light energy from the Sun into chemical energy in the form of glucose. The video mentions that 'primary producers depend on sunlight' and that they 'turn light from the Sun into oxygen and natural sugars.' This process is vital for life on Earth and is directly affected by the amount of sunlight received during different seasons.

💡Carbon dioxide absorption

Carbon dioxide absorption is a process where primary producers take in CO2 from the atmosphere during photosynthesis. The video script discusses how 'Earth orbiting satellites measure the amount of carbon dioxide absorbed by these primary producers,' indicating the importance of this process in the global carbon cycle and its impact on climate.

💡Productivity

Productivity in the context of the video refers to the rate at which primary producers create biomass through photosynthesis. The script uses the example of the North Pacific, where 'productivity skyrockets' in spring, illustrating how seasonal changes affect the growth and activity of primary producers, which in turn influences the entire food web.

💡Ocean food web

The ocean food web is a complex network of interactions between organisms in the marine ecosystem. The video script mentions phytoplankton, which 'form the base of the ocean food web,' highlighting how changes in primary producers can ripple through the entire ecosystem, affecting the abundance and diversity of marine life.

💡Continental brightness

Continental brightness is a measure of how green or lush the land appears, which is related to the amount of photosynthesis occurring. The video script describes how 'continents in this field turn dark from a lack of photosynthesis' during winter, indicating a decrease in plant activity and thus a change in the visual appearance of the land.

Highlights

Earth's orbit around the Sun takes a full year, influencing seasonal changes.

Earth's axial tilt remains constant as it orbits the Sun, affecting sunlight distribution.

Winter in the northern hemisphere is characterized by the North Pole tilting away from the Sun, resulting in shallow sunlight angles and shorter days.

Spring in the northern hemisphere is marked by equal day and night lengths due to Earth's neutral tilt relative to the Sun.

Summer in the northern hemisphere sees the North Pole tilting towards the Sun, leading to more direct sunlight and longer days.

The southern hemisphere experiences the opposite season to the northern hemisphere due to Earth's tilt.

Earth's tilt creates reversed seasons, with summer in one hemisphere and winter in the other.

Plant life and primary producers, such as phytoplankton, depend on sunlight and respond to seasonal changes.

Satellites measure the carbon dioxide absorbed by primary producers, indicating their productivity.

In spring, the North Pacific's productivity increases as sunlight strikes the cold waters, benefiting phytoplankton.

Phytoplankton, as microscopic photosynthesizers, form the base of the ocean food web and are sensitive to seasonal changes.

On land, forests respond to seasonal changes by growing green in spring and turning dark in winter due to reduced photosynthesis.

Seasonal changes affect the color of continents, with spring bringing greenery and winter causing darkness.