Every year on February 2nd, people in Punxsutawney, Pennsylvania, dress up in old-fashioned clothes and bring out a groundhog named Phil to predict the end of winter. While it’s a fun tradition, relying on a groundhog for weather predictions isn’t exactly scientific.
The concept of seasons originally came from farming. Farmers needed to know the best times to plant their crops, so they divided the year into different seasons. Most of us think of winter as the coldest time, summer as the hottest, and spring and autumn as the in-between periods. You probably learned this early on in school.
However, the seasons on our calendars don’t always match up with the weather we experience. In many parts of the northern hemisphere, like the U.S., the coldest part of the year starts before the official beginning of winter, and summer doesn’t cover all the warm days.
So, why don’t our calendar seasons match the weather? It all has to do with Earth’s tilt. As Earth orbits the sun, its axis tilts, causing different parts of the planet to receive varying amounts of sunlight throughout the year. This tilt results in shorter days in winter and longer days in summer.
In theory, winter should be the darkest time of the year, and summer should have the most daylight. Some cultures even define their seasons this way. For example, in Shakespeare’s play, the summer solstice is referred to as “midsummer.” But Earth doesn’t heat up or cool down instantly. It takes time for the sun’s energy to change temperatures, especially near large bodies of water like oceans and lakes, which absorb and release heat slowly.
During winter, water retains heat, preventing temperatures from dropping too quickly. This delay means that the coldest and hottest periods don’t align perfectly with the solstices. Our modern four-season system has roots in Roman times. The Romans lived in areas surrounded by water, so their seasons matched the solstices more closely. This system was then applied to many other regions, even if it didn’t fit perfectly.
Depending on whether you focus on astronomy or temperature, there are various ways to define seasons, but none are flawless. Many animals and plants don’t worry about these definitions; they simply adapt to the natural climate cycles. Some indigenous Australian cultures define their seasons based on the appearance of certain plants and animals, which makes a lot of sense.
So, while Groundhog Day is a fun tradition, it’s important to stay curious and understand the science behind the seasons!
Create a simple model using a globe and a flashlight to demonstrate Earth’s tilt and its orbit around the sun. Observe how the tilt affects sunlight distribution. Discuss with your classmates how this relates to the changing seasons.
Research and collect temperature data for your region over the past year. Plot this data on a graph and compare it to the official calendar seasons. Analyze any discrepancies and discuss possible reasons for these differences.
Investigate how different cultures around the world define and celebrate their seasons. Present your findings to the class, highlighting any unique traditions or definitions that differ from the four-season system.
Observe local plants and animals to identify natural indicators of seasonal changes. Document your observations and create a presentation explaining how these indicators align or differ from the calendar seasons.
Participate in a class debate on whether the calendar seasons accurately represent the natural changes in your environment. Use scientific evidence and cultural examples to support your arguments.
[INTRO MUSIC]
Every year on February 2nd, the people of Punxsutawney, PA, dress up as if it’s 1886, pull a groundhog named Phil out of a box, and ask him when winter will end. Not surprisingly, meteorologically-inclined marmots are not reliable predictors of spring.
[INTRO MUSIC]
But why divide the year into seasons in the first place? The word “season” originated on the farm, as surviving another trip around the sun meant knowing when to sow seeds. In most people’s minds, winter is when it’s coldest, summer is when it’s hottest, and spring and autumn occur in between. You probably figured that much out before kindergarten.
However, those aren’t the seasons on your calendar. In most of the northern hemisphere, especially in the U.S., the coldest quarter of the year begins several weeks before the “official” start of winter, and summer leaves out a good chunk of warm weather.
How did our seasons get so detached from… our seasons? Because Earth’s axis points alternately toward and away from the sun, we know there’s less daylight in winter and more daylight in summer. So shouldn’t winter be the darkest time of year, and summer the time with the most daylight? If we did that, then the solstices *should* fall at the midway point.
Several cultures define their seasons this way, and it might sound familiar from a certain William Shakespeare play where the summer solstice falls at “midsummer.” But like a big brisket, Earth cools and heats very slowly, and it takes time for changing solar energy to affect the temperature. Water absorbs even more heat than land, so places near oceans and lakes experience greater lags between increased solar energy and warmer weather.
The opposite happens in winter; all that water stores heat and keeps things from getting cold as soon as the sun starts to fade. The start of cold or hot periods gets shifted toward the solstices, but in most places, they *still* don’t line up with the coldest and warmest quarters.
It probably won’t surprise you to learn that a lot of our modern four-season system traces its origins to the Romans. Because so much of their territory was insulated by large bodies of water, the temperatures they experienced lined up neatly with the solstices, which were significant to ancient astronomers and festival-lovers. This system was applied to a whole hemisphere, even though it didn’t make sense in many places.
Depending on whether you care more about astronomy or temperature, there are various ways to define seasons, and none of them are perfect. Of course, most other living creatures don’t worry about any of this; they just follow Earth’s natural climate cycles where they live. Several indigenous Australian cultures define their seasons based on the presence of certain plants and animals at any given time.
They’d probably think Groundhog Day makes a lot of sense. Stay curious.
Seasons – Periods of the year characterized by specific weather conditions and daylight hours, resulting from the Earth’s tilt and orbit around the Sun. – The changing seasons are caused by the Earth’s tilt as it orbits the Sun, leading to variations in temperature and daylight.
Earth – The third planet from the Sun in our solar system, home to diverse ecosystems and life forms. – Earth is unique in our solar system because it supports a wide variety of life forms due to its atmosphere and water resources.
Sunlight – The light and energy that come from the Sun, essential for life on Earth and influencing weather and climate. – Sunlight provides the energy needed for photosynthesis, which is crucial for plant growth and oxygen production on Earth.
Tilt – The angle at which the Earth’s axis is inclined relative to its orbital plane, affecting the intensity and distribution of sunlight on the planet’s surface. – The tilt of the Earth’s axis is responsible for the varying lengths of day and night throughout the year.
Temperature – A measure of the warmth or coldness of an environment, influenced by factors such as sunlight, altitude, and atmospheric conditions. – Temperature differences between the equator and the poles drive atmospheric circulation patterns on Earth.
Winter – The coldest season of the year, occurring when one hemisphere is tilted away from the Sun, resulting in shorter days and lower temperatures. – During winter in the Northern Hemisphere, the North Pole is tilted away from the Sun, leading to colder weather and shorter days.
Summer – The warmest season of the year, occurring when one hemisphere is tilted toward the Sun, resulting in longer days and higher temperatures. – In summer, the increased sunlight and longer days cause temperatures to rise, making it the hottest season of the year.
Solstice – An astronomical event that occurs twice a year, when the Sun reaches its highest or lowest point in the sky at noon, marking the longest and shortest days. – The summer solstice occurs around June 21st, when the Northern Hemisphere experiences its longest day of the year.
Climate – The long-term average of weather patterns in a particular region, including temperature, precipitation, and wind. – The climate of a region is determined by its latitude, altitude, and proximity to bodies of water, among other factors.
Astronomy – The scientific study of celestial objects, space, and the universe as a whole. – Astronomy helps us understand the origins of the universe and the physical laws that govern celestial bodies.
