Goodbye winter, with your bitter winds, subarctic temperatures and mounds of snow, and hello Spring!
This month we are gearing up for the official start of Spring in the Northern Hemisphere. Though no guarantee of gorgeous weather and milder temperatures, the Earth’s position relative to the sun says it’s officially time for the birds to start chirping.
The first day of spring arrives on varying dates (from March 19-21) in different years for two reasons: Our year is not exactly an even number of days; and Earth’s slightly noncircular orbit, plus the gravitational tug of the other planets, constantly changes our planet’s orientation to the sun from year to year.
In 2014, spring begins on March 20 at 12:57 P.M. EDT. That’s when our Planet’s Vernal Equinox will occur. Each year, we experience two Equinoxes which mark the onset of spring and autumn and two solstices which mark when summer and winter begin. Each of these are points in time and space that mark a transition in our planet’s annual trip around the sun.
As the Earth orbits the Sun, the tilt of the Earth changes. Sometimes the Earth tilts on its axis towards the Sun and sometimes away from the Sun. On the Equinox, the axis of the Earth is exactly parallel with the Sun. During the Autumn Equinox & the upcoming Spring Equinox, the Earth is NOT tilted! So, what does this mean for all of us on Earth? Glad you asked!
On the Equinox, the length of the day is exactly 12 hours at every point on Earth. The word “Equinox” is derived from the Latin words aequus, meaning “equal,” and nox, meaning “night.” At each equinox, the sun crosses the Earth’s equator, making night and day of approximately equal length on most of the planet. At the equator, the sun is directly overhead at noon on either equinox. However, day and night are not exactly equal on the date of the equinoxes. For instance, at higher latitudes in the Northern Hemisphere, the “equal day and night” occurs a few days before the spring equinox, while in the Southern Hemisphere that date comes after the March equinox, according to the National Weather Service. [Earth’s Equinoxes & Solstices (Infographic)]
So How Does it Work?
Earth’s multiple motions — spinning on its axis and orbiting the sun — are behind everything from day and night to the changing seasons. The sun comes up each day because Earth rotates once on its axis every 24 hours or so. Seasons are a result of the Earth being tilted 23.5 degrees on its spin axis coupled with the planet’s 365-day orbit around the sun.
Imagine Earth as an apple sitting on one side of a table, with the stem being the North Pole. Tilt the apple 23.5 degrees so the stem points toward a candle (the sun) at the center of the table. That’s summer for the top half of the apple.
Keep the stem pointing in the same direction, but move the apple to the other side of the table: Now the stem points away from the candle, and it’s winter on the top half of the fruit. The very top of the apple, representing the north polar region, is in total darkness 24 hours a day, during that season.
At winter solstice, the sun arcs low across the Northern Hemisphere sky for those of us below the Arctic Circle, and the stretch of daylight is at its shortest. By the time of the spring equinox, the days have grown noticeably longer. At the summer solstice, the sun reaches its highest possible point in our sky, yielding the longest day of the year in the Northern Hemisphere.
As long ago as the fourth century B.C., ancient Native Americans understood enough of this that they could create giant calendars to interact with the cycle of sunlight. They built observatories of stone to mark the solstices and other times important for planting or harvesting crops. Shrines and even tombs were also designed with the sun in mind.
Once Spring has officially arrived, the Northern Hemisphere will continue to tilt towards the Sun more and more resulting in warmer temperatures and the awakening of those tell-tale signs of the season that we all know & love!
Signs of Spring
Spring is also the time when worms begin to emerge from the earth, ladybugs land on screen doors, green buds appear, birds chirp, the flowers begin to bloom, and the weather provides just the right amount of sun and water to make it all happen. The vernal, or spring, equinox signals the beginning of nature’s renewal in the Northern Hemisphere.
With all of this science happening in the world around us, it’s easy to see why this month is ideal to bring the lesson out of the classroom & into your daily routine. Hands-on inquiry is perfect for cultivating curiosity & experiencing the Science of Spring firsthand. Why not use the extra hours in your day to plant a garden to explore various plants & their growth patterns, conduct your own insectigations & track the sightings of your favorite creepy-crawlies, keep an ongoing cyber weather journal to share with your fellow mini-meteorologists or simply take the science to social media with photo sharing of the spring landscape in your neighborhood.
Spring time is the perfect time to celebrate with Science FUN!
How do you know that spring is coming? How will you celebrate the First Day of Spring?
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