How earth's tilt causes seasons | Cosmology & Astronomy | Khan Academy

TL;DR

The tilt of the Earth determines the seasons, with the Northern Hemisphere experiencing summer when tilted towards the sun and winter when tilted away.

Transcript

In the last video, we talk about how seasons on Earth are not caused by how close Earth is to the sun in its orbit. And we also hint at the fact that it's actually caused by the tilt of the earth. And so in this video, I want to show you how the tilt of the earth causes the seasons to happen. So let's draw-- so I'm going to try to draw as many diag... Read More

Key Insights

• 🍹 The tilt of the Earth's rotational axis determines which hemisphere experiences summer and winter.
• 🌞 When the Northern Hemisphere is tilted towards the sun, it receives more sunlight and experiences summer, while the Southern Hemisphere has winter.
• 😎 The amount of sunlight received, the angle of the sun's rays, and the dissipation of energy through the atmosphere contribute to differences in seasons.
• 🍰 The tilt of the Earth remains relatively constant over short periods, but changes over long periods of time.
• ✋ The changes in seasons are more extreme at higher latitudes, such as the Arctic Circle.
• 😎 Spring and fall occur when the tilt of the Earth is neither towards nor away from the sun.

Questions & Answers

Q: How does the tilt of the Earth cause different seasons in the Northern and Southern Hemispheres?

The tilt of the Earth determines which hemisphere is tilted towards the sun, experiencing summer, while the other is tilted away, experiencing winter. This tilt affects the amount of sunlight and the angle of the sun's rays received by each hemisphere, resulting in different seasons.

Q: Does the tilt of the Earth change over time?

The tilt of the Earth remains relatively constant over short periods, but it changes over long periods of time. The tilt varies between approximately 22.1 and 24.5 degrees, with a complete cycle taking 41,000 years. However, for understanding annual seasons, the current tilt of 23.4 degrees is sufficient.

Q: How does the tilt of the Earth impact the length of daylight and darkness in different seasons?

When the Northern Hemisphere is tilted away from the sun, it receives less daylight, leading to shorter days and longer nights. Conversely, when the Northern Hemisphere is tilted towards the sun, it receives more daylight, resulting in longer days and shorter nights.

Q: Apart from the tilt of the Earth, what other factors contribute to the differences between seasons?

In addition to the tilt, the amount of sunlight reaching each hemisphere and the angle of the sun's rays play significant roles. The Southern Hemisphere receives a greater proportion of sunlight when the Northern Hemisphere is tilted away, while the opposite occurs when the Northern Hemisphere is tilted towards the sun. The angle of the sun's rays also affects the dissipation of energy through the atmosphere, influencing the intensity of seasons.

Summary & Key Takeaways

• The tilt of the Earth's rotational axis causes seasons to happen.

• When the Northern Hemisphere is tilted towards the sun, it experiences summer, while when tilted away, it experiences winter.

• The amount of sunlight, the angle of the sun rays, and the dissipation of energy through the atmosphere all contribute to the differences in seasons.