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Spring!
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Spring is the time of year when the Earth begins to show the beauty and bounty that have long been hidden by winter’s snow and cold. In ancient times before science provided an understanding of the world around us, people celebrated spring as a time when the world was renewed: crops could be planted and livestock would produce their young. It was a time of promise, hinting that the cold winter when the Earth seemed to be dead was over. They did not understand the effects of Earth’s revolution around the sun, which causes our seasons. They did not believe that spring would come for certain every year. Diana |
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What is the Vernal Equinox?
The Vernal (Spring) Equinox occurs on March 20 at 10:00 PM EST this year. Other years it may occur on March 21. It is not the date but the position of the sun with respect to the Earth that determines the date and time of this event. Astronomically, the sun will be directly overhead in the sky at the Equator (0 degrees latitude) at solar noon on the date of the Vernal Equinox.
As the Earth rotates around the sun, the sun appears in different parts of the sky. Looking at the sun at mid-day or noon on a daily basis is a good way to observe the sun’s position in the sky and make comparisons from day-to-day or season-to-season. The day the sun is straight up over the Equator at noon is the first day of spring - the Spring Equinox.
There is another equinox in the fall. The Autumnal Equinox is the day the sun is again highest in the sky at noon over the Equator.
 Because the Earth is tilted on its axis, it always "leans" in the same direction as it revolves around the sun. So as the Northern Hemisphere is tilted away from the sun, it is winter in that hemisphere and it is summer in the Southern Hemisphere. In the summer, the Northern Hemisphere is tilted toward the sun. For the United States and other countries north of the Equator, the rays from the sun that hit the Earth during the summer are the most direct and we feel more warmth and see more light during this time. During the Equinoxes, the Earth is halfway between the time when the Earth experiences the sun’s most direct and least direct rays. Weather conditions tend to be somewhere “in the middle” of winter and summer at these times. When the sun appears directly over the Equator at noon, the length of time for hours of light (day) will equal the length of time for hours of no light (night). The sun will rise and set exactly 12 hours apart on that day.
You can see why ancient civilizations had a difficult time understanding what was really happening. Even with science to help us, the seasons can be difficult to understand.
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Classroom Activity
The Astronomy of the Seasons
Materials Needed:
- A globe on a tilted axis
- A flashlight or small, bright lamp
Objective: You will be able to visualize how the Earth is illuminated by the sun. This activity helps to explain some of the phenomena associated with the seasons, e.g. why the sun shines throughout the night in the Arctic circle during the start of the Northern Hemisphere's summer and why at the same time no sunlight falls in the middle of the day within the Antarctic circle.
- In a darkened room, illuminate a globe with a single light placed a few feet away. Place the light at the same height as the globe. The part of the globe facing the lamp will be lighted just as the Earth is lighted by the sun. Turning the globe slowly about its axis causes the light to move across the globe’s surface, just as daylight moves across the Earth as the Earth rotates on its axis.
- Turn the base of the globe's mounting until the North Pole is tilted toward the light. This corresponds to around June 21 and the first day of summer in the Northern Hemisphere. The Southern Hemisphere experiences less direct light. This represents winter.
- Turn the base 180 degrees so the North Pole is tilted away from the lamp. This corresponds to December 21 and the first day of winter when days have the least number of daylight hours in the Northern Hemisphere. On this day, summer begins in the Southern Hemisphere. The light shines more directly on that hemisphere now.
- Turn the base halfway between these two positions. This corresponds to the equinoxes, approximately, March 21 and September 21. At those times the dividing line between night and day will pass through both poles and everyone on Earth experiences days with 12 hours of daylight and 12 hours of darkness.
Try it! It’s a great way to visualize the Earth’s movement around the sun and the effects on our planet.
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Weather Wizard
Hemisphere - Either the northern or southern half of the Earth as divided by the Equator, or the eastern or western half as divided by a meridian from North Pole to South Pole.
Equinox - A term originally referring to the two times of year when night and day are the same length. The modern definition of the equinoxes is the instant at which the center of the sun crosses the Equator.
Equator - An imaginary line around the Earth midway between the North and South Poles. It divides the Earth into the Northern Hemisphere and the Southern Hemisphere. The Equator passes through the continents of Africa and South America, and also the islands of Indonesia.
Season - One of the four periods into which the year is divided based upon the position of the sun in the sky. The four seasons are spring, summer, autumn (also called fall), and winter.
Horizon - The area corresponding to the farthest distance one can see in a given direction.
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Weather Trivia
Meteorologists distinguish between meteorological spring and astronomical spring because:
- Astronomical spring falls on different dates each year.
- It "feels like spring" in many places before astronomical spring begins.
- The date for astronomical spring changes and it is easier to keep seasonal comparisons based on the same date.
- All of the above
Answer: D - All of the above.
The first day of astronomical spring falls on either March 20 or March 21 depending on the year. Meteorological spring always falls on March 1. Plus, it feels like spring, as mild surges of air from the south become a regular occurrence for much of the US in the three weeks before March 20/21.
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WeatherNet Classroom News
WeatherNet schools across the country are qualifying as Homeland Security WeatherNet Network sites. Many were recently honored at award ceremonies.
 Chris Cimino from, WNBC, Channel 4 in New York City was present to see Assumption School in Emerson, NJ receive its Homeland Security WeatherNet Network star and flag. Sister Anne Therese, Principal and Brother Ralph Darmento are pictured here with Mayor Setteducati, Officers Gallagher and Duardo, WeatherNet’s Gary Milwit and Chris.
Willow Springs Elementary Principal, Charles Langley and Guidance Counselor, Luanne Crutchfield accepted their Homeland Security WeatherNet Network "star award" and flag from NBC 17- Raleigh meteorologists Frank Cariello, Janice Jones and Dave Osterburg. Willow Springs Elementary in Willow Springs, NC is the first school in the Raleigh area to be certified.
Your school can be a part of this partnership as well. Request a Homeland Security WeatherNet Network certification packet from WeatherNet, or complete the packet you previously received from us. It should take about an hour for you to answer the required questions and return the packet to us. We will evaluate your school's information to ensure your equipment is working properly. If so, your site will be certified and you will receive a star award and flag from WeatherNet and your local TV partner.
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Careers in Weather
The Vernal Equinox is often referred to as the first day of astronomical spring. This is because the sun will appear to be directly above the Equator at solar noon. As the Earth continues to rotate on its axis, orbiting the sun, the North Pole tilts toward the sun causing temperatures to rise and spring to occur in the Northern Hemisphere. The people who study this movement of the planets, as well as the movements of stars and other celestial bodies are known as astronomers or astrophysicists.
 Astronomy is the study of celestial bodies (sun, stars, moons and planets to name a few) and their compositions, motions and origins. There are many different concentrations within the field of astronomy including planetary science, solar astronomy, the origin and evolution of stars, and the formation of galaxies. Within each field there are observational astronomers who record information that they observe either through the use of a telescope or spacecraft such as satellites or the space shuttle. Other astronomers are known as theorists and they work with the collected data to formulate theories about what is happening in space.
Astronomy is a difficult profession to enter. There are only about 6,000 professional astronomers in North America. In order to become an astronomer, you must have a good background in math and science, especially physics. Most professional astronomers have a Ph.D. degree, meaning they have gone to college for at least ten years. The majority of professional astronomers are employed by colleges and universities where they do research and teach. Many more astronomers are employed in government and federally supported observatories and laboratories. Private companies, particularly those with expertise in the aerospace and defense industries, employ the remaining ten percent of all astronomers.
A unique area of astronomy is the study of space weather. Not the weather we experience here on Earth, but solar storms and asteroid showers and how they affect the planets. Read more about space weather.
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