Frog Went A-Courting

One of spring's most characteristic sounds is the song sung by frogs. If you walk into the woods or beside a field or along a ditch or stream on any warm evening, you may hear the calling of frogs. Except for a few species, only males make vocalizations, and they may use several different types of calls. One specific call is used to defend territory. Another is used in distress, such as when a frog is attempting to escape from a predator. A third type is used by a male to let another amorous male know it is not a female, but the most commonly used is the vocalization intended to attract a female.

Each species of frog makes a distinctive sound which is produced by moving air through a vocal sac that inflates below the frog's mouth. The call enables females to find suitable mates. It also lets people identify the different species of frogs present in an area even if the individuals can't be seen.

Frog species have different breeding seasons. Wood Frogs, for example, breed for a short period in late winter. Many treefrogs breed in late spring or summer. Spring Peepers have a long breeding season, from February to June. Some frogs, such as the Eastern Spadefoot, are identified as "explosive breeders" because large numbers come together en masse for brief times during heavy rains.

Resources
Listen to the calls of various frog species: "Frog Call Lookup," produced by the Patuxent Wildlife Research Center of the U.S. Geological Survey

Identify a frog: "All Living Things: Anura," a tool for species identification developed by Discover Life, a project sponsored by the National Science Foundation; University of Georgia, Athens; and others.

Learn about the importance of frogs in the environment: "Virginia Is for Frogs," produced by Virginia's Department of Game and Inland Fisheries.

Subscribe today! Pier Press seeks to facilitate informed conversation at the intersection of science and spirit by promoting Biblical and scientific literacy. This article is excerpted from one that appeared in the April 21, 2017 issue of Observations: A Pier Press® Newsletter. Subscribe today to have future newsletter issues delivered directly to your inbox.

Determining the Date for Easter

The date for Easter changes annually because of differences between lunar and solar cycles. This creates a sequence of "movable" observances. Based on guidance established by the Council of Nicaea in 325 AD/CE, the Easter celebration occurs on the first Sunday that follows the first new moon after the spring equinox, which the ancient council established as March 21 (an astronomical approximation).

The Julian Calendar used at that time had been adopted in 45 BC/BCE by Julius Caesar. It was based on a year length of 365.25 days. Because the true length of a solar year is 365.2422 days (11 minutes and 14 seconds shorter than the calendar's calculations), the astronomical spring equinox occurred slightly earlier than predicted by the calendar. By the mid sixteenth century, a difference of 13 days had accrued.

Pope Gregory advocated for calendar reform. The Gregorian Calendar, adopted by the Roman Catholic Church in 1582, subtracted 13 days to realign the calendar's spring equinox more closely to the astronomical equinox, and it adjusted the calculations for leap years. Today, the Gregorian Calendar is the most commonly used civil calendar.

As a result of applying the formula for calculating the date on which Easter will be observed to different calendar systems, Western and Eastern Easter celebrations often fall on different dates. Western traditions, which include Roman Catholic and Protestant communities, follow the Gregorian calendar, and Easter can occur as early as March 22 or as late as April 25. For Eastern branches of Christianity, which include Orthodox churches, the observation of Easter can occur as early as April 3 or as late as May 10.

This year [2017] is unusual, because the same full moon will fall after the spring equinox in both calendar systems, resulting in coinciding dates for the Easter observation.

—Pier Press seeks to facilitate informed conversation at the intersection of science and spirit by promoting Biblical and scientific literacy. This article is excerpted from one that appeared in the April 7, 2017 issue of Observations: A Pier Press® Newsletter. Subscribe today to have future newsletter issues delivered directly to your inbox.

Crescent Moon and Two Planets

If your skies are clear and you have a good view of the western horizon, you're in for a special celestial sight on the evening of March 29, 2017. Just after sunset (which will occur approximately between 7:00 and 8:00 p.m. depending on your location) look for the moon's thin first crescent.

As the sky continues to darken and the stars pop out, look diagonally down to the right (toward the horizon). You should be able to find the planet Mercury. Because the planet will appear low in the sky, you'll have an easier time locating it if your view is unobstructed, such as across an open field or large body of water.

Above the moon (see image below), you'll be able to spot the reddish glow of Mars. Connecting the dots, the slender crescent moon, Mars, and Mercury will form a triangle. If you consider the line created by Mercury and Mars to be the baseline, the moon will be to the left. If you extend the baseline up father in the sky, about half way to overhead, you'll arrive at another reddish spot. This is the star Aldebaran, the eye of Taurus the bull.

But don't wait too long. Mercury will set less than an hour and a half after the sun, the moon less than a half an hour after that, followed an hour later by the setting of Mars.

Once you know the relative positions of these celestial points, you can watch as they change over the course of the next few days and weeks. On March 30, the moon will appear higher in the sky than Mars, and by March 31, the moon will approach the star Aldebaran. By about April 10, Mercury will become lost in twilight glow, and by mid-month it will sink below the horizon. Relative to the background stars, Mars will travel approximately toward Aldebaran. On April 22, Mars will be just to the left of the Pleiades cluster, and on May 1, Mars will appear to the right of Aldebaran.

Pier Press seeks to facilitate informed conversation at the intersection of science and spirit by promoting Biblical and scientific literacy. This article appeared in the March 28, 2017 issue of Observations: A Pier Press® Newsletter. Subscribe today to have future issues delivered directly to your inbox.