Sun rises at 5:36am
Sun sets at 6:42pm
Moon phase: first quarter moon, crescent waxing
Moon rises at 8:35am
Moon sets at 9:45pm
The Moon & the Tides
As the Sun sets on Saturday night, look to the western sky to see the new moon, just starting its 28-day cycle. A thin sliver of lunar landscape hovers near the foot of the constellation of Gemini, the Twins. Are those Gemini boys playing soccer with the earth’s natural satellite? Perhaps Cassiopeia should scold them!
The new moon is showing the earth its unlit face, with only a hint of the lighted side peeking around the edge. No matter how the moon looks to us earthlings, the sphere of rocky material that orbits us is always half lit by the sun, just as all the planets in the solar system. The changes we see in its appearance are due to how much of the lit face is aimed our way.
A full moon shows us the entire lit side, which is approximately two weeks from the true new moon, which is invisible to us, as its fully lit side is aimed away from earth. The dance of the earth, moon, and sun is a remarkable and rhythmic pirouette in which the three celestial bodies use gravity and momentum to swing around each other – the moon and earth do it every 28 days and together they swing around the sun every 365 days. And so go the days, months and years of our lives.
Because our oceans respond to the gravity of the sun and the moon, the tides are more extreme when the earth, moon and sun are in near-alignment, because their gravitational pulls add together. These are called spring tides, though it has nothing to do with the season of spring. Think of the water as springing forth! These spring tides occur when the moon is full but also when the moon is new. They are considered more extreme because the high tides are very high and the low tides are very low. Then one week later, the sun and the moon will be at right angles to each other, thus their gravitational pulls will not add together; in fact, they subtract! Physics is math, people! At that time, called neap tides, the high tides are not that high and the low tides are not that low.
Here in the Caribbean, we don’t notice that much of a difference in the high tides or the low tides. That is because our islands don’t really stop the movement of the ocean like a continent does. The water goes around us and keeps flowing. Long, continental coastlines, especially those running north and south receive the greatest tidal range. The greatest tides are said to be in the Bay of Fundy in Nova Scotia on the eastern coast of North America. This is one place where the difference between the high tides and low tides can be as much as 40 feet! You can bet the folks living there are quite aware of the moon’s phase, especially those who make their living near or on the sea.
Watch the moon set about the same time as the brightest star in the sky, Sirius, and about 30 minutes later, the bright star Procyon will follow them down to the western horizon. The heads of the Gemini boys will set about 10 o’clock.
Ten is a great time to go out to check the stars and planets, providing the clouds are not blocking the view. At that time, the bright star Arcturus will be directly overhead, a position known as the Zenith, and Jupiter and the star Spica will be very high up too, in the southwestern portion of the sky. Due south and low – just above the horizon – look for two bright stars, Hadar and Rigil-Kent, these are the pointers that show the way to the Southern Cross.
Thank you for keeping up with the Night Sky articles. If you are out later on in the week, each star rises about four minutes earlier each day than written here, and the moon rises 50 minutes later. Night Sky is researched and compiled by Lisa Davis-Burnett. Earthsky.org is a key resource for information and images. Questions or comments? Email This email address is being protected from spambots. You need JavaScript enabled to view it.
