BY admin | April 25, 2013
The eclipses, whether lunar or solar, has always remained a source of mystery, fascination and even fear, despite taking place several times since the evolution of the Universe. Not only is the eclipse capable of garnering the interest of the astronomers but also the common man.
The partial lunar eclipse taking place in April 25-26, considered to be the third shortest lunar eclipse of the 21st century, lasting 27 minutes, has generated a lot of interest among the people. There have been several myths and urban legends associated with the lunar eclipse, especially when total lunar eclipses turned the moon blood-red, an effect that terrified people who had no understanding of what causes an eclipse and therefore blamed the events on this god or that
Grounding the myths, as per the scientific calculations, a lunar eclipse can occur only at full moon. A total lunar eclipse can happen only when the sun, Earth and moon are perfectly lined up, anything less than perfection creates a partial lunar eclipse or no eclipse at all. Since the moon’s orbit around Earth lies in a slightly different plane than Earth’s orbit around the sun, perfect alignment for an eclipse doesn’t occur at every full moon. A total lunar eclipse develops over time, typically a couple hours for the whole event.
During the lunar eclipse, the Earth casts two shadows that fall on the moon during the period of eclipse: While the full, dark shadow is termed as Umbra, the partial outer shadow is called penumbra.. The moon passes through these shadows in stages. The initial and final stages — when the moon is in the penumbral shadow —are not so noticeable, so the best part of an eclipse is during the middle of the event, when the moon is in the umbral shadow.
We can consider ourselves lucky in the sense that at present the moon is at the perfect distance for Earth’s shadow to cover the moon totally, but just barely. Billions of years from now, that won’t be the case, since ever since the moon came into existence about 4.5 billion years ago, it has been inching away from our planet (by about 1.6 inches, or 4 centimeters per year).
The lunar eclipse takes place in several forms: total lunar eclipse in which the Earth’s full (umbral) shadow falls on the moon. The moon won’t completely disappear, but it will be cast in an eerie darkness that makes it easy to miss if you were not looking for the eclipse. During the partial lunar eclipse the sun, Earth and moon are not quite perfectly aligned, and Earth’s shadow appears to take a bite out of the moon.
The other form of lunar eclipse, which is quite interesting is the Penumbral lunar eclipse because the moon is in Earth’s faint outer (penumbral) shadow. However, the most interesting or rather intriguing eclipse is the blood-red moon, in which the moon turns red or coppery colored during the total portion of an eclipse. The red moon is possible because while the moon is in total shadow, some light from the sun passes through Earth’s atmosphere and is bent toward the moon. While other colors in the spectrum are blocked and scattered by Earth’s atmosphere, red light tends to make it through easier. According to NASA scientists, the exact color of the moon appears depends on the amount of dust and clouds in the atmosphere. If there are extra particles in the atmosphere, from say a recent volcanic eruption, the moon will appear a darker shade of red.
While the Lunar eclipse is at the advantage of being watched through naked eyes, thereby eliminating nay requirement of protective gear, Solar Eclipse may render damage to eyes if seen without any protection. A solar eclipse occurs when the moon gets between Earth and the sun, and the moon casts a shadow over Earth. A solar eclipse can only take place at the phase of new moon, when the moon passes directly between the sun and the Earth and its shadows fall upon the Earth’s surface. The next solar eclipse will be an annular eclipse on May 10, 2013.
Just like the lunar eclipse, the solar eclipse too is categorized as per the occurrence and appearance. During the Total Solar Eclipse, the moon casts its umbra upon Earth’s surface; that shadow can sweep a third of the way around the Earth in just a few hours. Those who are fortunate enough to be positioned in the direct path of the umbra will see the sun’s disk diminish into a crescent as the moon’s dark shadow rushes toward them across the landscape. On the average a total eclipse occurs somewhere on Earth about every 18 months.
The Partial solar eclipses occur when only the penumbra (the partial shadow) passes you by. In these cases, a part of the sun always remains in view during the eclipse. How much of the sun remains in view depends on the specific circumstances. Further an Annular solar eclipse is similar to total eclipses in that the moon appears to pass centrally across the sun, but it’s too small to cover the disk of the sun completely. Because the moon circles the Earth in an elliptical orbit its distance from Earth can vary from 221,457 miles to 252,712 miles. But the dark shadow cone of the moon’s umbra can extend out for no longer than 235,700 miles; that’s less than the moon’s average distance from Earth. During such an eclipse, the antumbra, a theoretical continuation of the umbra, reaches the ground, and anyone situated within it can look up past either side of the umbra and see an annulus, or “ring of fire” around the Moon.
The other variety of the eclipse are the Hybrid solar eclipses also known as annular-total (“A-T”) eclipses. This special type of eclipse occurs when the moon’s distance is near its limit for the umbra to reach Earth. In most cases, an A-T eclipse starts as an annular eclipse because the tip of the umbra falls just short of making contact with the Earth; then it becomes total, because the roundness of the Earth reaches up and intercepts the shadow tip near the middle of the path, then finally it returns to annular toward the end of the path. Of all solar eclipses, about 28 percent are total; 35 percent are partial; 32 percent.