SCI-KIDS: Signs of spring send clear signals

Spring has officially arrived, hooray! As of Friday night, the sun will be overhead in the Northern Hemisphere for six months, our seasons of spring and summer.

How do you measure the ar rival of spring? There are many ways.

Although astronomers forecast the "official" arrival of spring with great accuracy, we have many low-technology ways to remind us that spring is here.

Here are some of my favorites.

First, I watch the sun and its shadows, not in a precise way, but in a general way. My bedroom windows face east. As spring arrives, the rising sun appears over a hill to my east and its light floods straight across the bedroom. The beginning of spring and the beginning of fall are the only time the sunbeams show this pattern.

Out on the terrace, which runs east-west, I watch for the shadows of the setting sun. At the beginning of spring and fall, the sunset shadows fall nicely in line with the edge of the terrace.

There is one other sunlight clue. As the sun moves northward, we receive more daylight and have shorter nights. The first of spring is when our day and night are exactly the same length (12 hours each). Our word for the first day of spring, the spring equinox, has within it this same meaning (equi for equal; nox for night; day equals night).

Sunlight is not the only clue to spring's arrival.

The sun has been moving northward in our skies for three months, and the atmosphere is getting warmer. Many plants and animals respond to this additional warmth, so we see buds where there were bare branches before.

Some plants respond very quickly to the added warmth. Out in the country, our jonquils are all open; in the warmer Richmond area, they appeared even sooner. Early spring bloomers also include bright yellow forsythia. Iris is up 3 inches. Day lilies the same.

Trees and bushy plants are putting out subtle signs. New bud tips are appearing along branches. Our lilac bushes have put forth leaves that are now about ½-inch across.

Our weather is changing. Not only to become warmer, but also to show many other changes linked to more solar energy. Rains are more frequent, but less icy. Winds are stronger and gustier.

No matter how you keep score: sunrise, sunset, length of day, alignment of shadows, early spring flowers, or trees starting to add new leaves, spring is here. Winter is over!

The Virginia science Standards of Learning cover seasons and seasonal changes beginning in first grade (topic 1.7) and continue through all grades.