Earths Seasons
Have you ever wondered why it snows in December but gets blazing hot in July? A lot of people think it is because the Earth gets closer to the sun, but that is actually completely wrong! Let us take a trip into outer space to discover the real reason we experience summer, autumn, winter, and spring.
Why Does the Weather Change Every Year?
Absolutely not! The distance between the Earth and the sun changes very slightly throughout the year, but we are actually closest to the sun during the cold winter months in the Northern Hemisphere.
No! When people in North America and Europe are sweating in the hot summer sun, people in Australia and South America are wearing heavy coats for their freezing winter.
Put Your Instincts to the Test
Think about what you already know about space and the weather. Pick an answer for each question, then see if your instincts were right.
The Earth is tilted on its axis! Our planet leans over at a precise angle, which changes exactly how much direct sunlight we get throughout the year.
It is winter! Because the Earth is tilted, when the Northern half leans towards the sun, the Southern half leans completely away from it.
No, we are actually closer in the winter! The distance does not cause the seasons, only the angle of the sunlight matters.
Understanding the Science
Let us break down the science of orbital paths, axial tilt, and solar energy with Bill Nye the Science Guy.
Key Concepts
Axis
Tap to learn moreAn axis is the imaginary line that goes straight through the centre of the Earth from the North Pole to the South Pole. The Earth constantly spins around this line.
Tilt
Tap to learn moreThe Earth does not sit straight up and down! It has a tilt of exactly 23.5 degrees, and this precise lean is the true cause of every single season.
Orbit
Tap to learn moreAn orbit is the elliptical, slightly squashed path the Earth takes as it travels completely around the massive sun. It takes exactly one full year to complete this journey.
Direct Sunlight
Tap to learn moreDirect Sunlight happens when a part of the Earth is tilted straight towards the sun. The light hits it head on, and this highly concentrated heat creates the warm summer season.
Indirect Sunlight
Tap to learn moreIndirect Sunlight happens when a part of the Earth is tilted away from the sun. The light hits it at an angle and spreads out, and this much weaker heat creates the cold winter season.
Hemisphere
Tap to learn moreA hemisphere is half of the Earth. The equator is an imaginary line that divides our planet perfectly into a Northern half and a Southern half.
Solstice
Tap to learn moreA solstice happens on the two days of the year when the sun reaches its absolute highest or lowest point in the sky at noon, marking the longest and shortest days of the year.
Equinox
Tap to learn moreAn equinox happens on the two days of the year when the sun crosses the celestial equator, making day and night exactly equal in length all over the entire world.
Try It: The Interactive Orbital Seasons Simulator
A very common scientific myth is that the Earth wobbles back and forth to create the seasons. It actually never changes direction! The axis stays locked pointing at the exact same spot in deep space all year long.
Because the tilt is completely fixed in space, as the Earth travels in a giant ellipse around the sun, the angle of the incoming sunlight constantly changes. Use the bright yellow slider below to drag the Earth along its orbit. Watch the Close Up View carefully to see exactly how the shadow sweeps over the permanently fixed axis, changing which hemisphere receives direct sunlight!
Live Global Data
Apply Your Knowledge
Let us see if you can match these seasonal concepts to their correct definitions.
Match the Concepts
Click an object to select it, then click the matching description to place it.
Real World Challenge
Imagine you are an architect building a house that uses the sun for natural heating and cooling. Knowing that the sun is much higher in the sky during summer and much lower during winter, how would you carefully design the windows and roof overhangs to keep the house cool in July but incredibly warm in December?
What Has Changed Since This Episode Aired
This episode first aired in the 1990s. While the Earth still tilts at exactly the same angle, modern science and technology have drastically changed how we observe and understand our climate!
Updated: Scientists are closely tracking how global warming is physically changing the timing of the seasons! Warmer global temperatures are causing spring flowers to bloom much earlier and pushing the start of autumn back by several weeks.
Updated: We use incredibly advanced satellites in space to monitor the exact temperature of the oceans and the atmosphere. This modern technology allows meteorologists to accurately predict severe seasonal storms and droughts months in advance.
Updated: Not at all! Modern rovers and advanced space telescopes have proven that Mars also experiences dramatic seasons because it is tilted on its axis, complete with freezing winters and polar ice caps that grow and shrink every year.
Test Your Understanding
Answer these questions and get instant feedback. How many can you get right?
Results
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Reflection
If the Earth was not tilted at all and sat perfectly straight up and down, how would your life, the weather, and the environment around you be completely different?
Episode Discussion
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