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

Summary

The 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.