There is also a difference for those on the center line depending on location east to west. Western Kentucky is optimally situated for this eclipse and those on the center line near Hopkinsville will have the chance to experience fractions of a second more totality compared to anywhere else at the center of the path of totality. In the animation below , the outline of the shadow of the moon as it moves across the surface of Earth is represented by the circle.
Two observers are indicated, observer 1 is closer to the edge of the path and observer 2 is at the centerline. This page requires JavaScript to be enabled in order to function properly. Also look for crescent-shaped shadows cast by light passing through gaps in the leaves on trees. What do the nodes of the lunar orbit have to do with eclipses? There are two orbit locations where eclipses can occur. These are the points in the lunar orbit that intersect the ecliptic plane where the Sun moves in the sky.
Called the ascending node and the descending node, eclipses can occur at either node. The Moon must be in the full moon phase as it passes the node in order for a lunar eclipse to occur. Similarly, solar eclipses only occur during new moon when this phase occurs at either node. Why do eclipse tracks move eastward even though the Earth rotates from west to east? You cannot keep up with the shadow of the eclipse unless you traveled at Mach 1.
How do computers predict eclipses? Astronomers first have to work out the geometry and mechanics of how the Earth and Moon orbit the Sun under the influences of the gravitational fields of these three bodies.
From Newton's laws of motion, they mathematically work out the motions of these bodies in three-dimensional space, taking into account the fact that these bodies have finite size and are not perfect spheres, and that the Earth and Moon are not homogeneous bodies. From careful observation, they then feed into these complex equations the current positions and speeds of the Earth and Moon, and then program the computer to "integrate" these equations forward or backward in time to construct ephemerides of the relative positions of the Moon and Sun as seen from the vantage point of the Earth.
Eclipses are specific configurations of these bodies that can be identified by the computer. Current eclipse forecasts are accurate to less than a minute in time over a span of hundreds of years. How long will we continue to be able to see total eclipses of the sun?
The orbit of the moon is not stable. Because of tidal friction, the orbit of the Moon is steadily growing larger, so that the angular size of the moon from the Earth is shrinking. The moon's orbit is increasing by about 3. When the moon's mean distance from Earth has increased an additional 14, miles, it will be too far away to completely cover the sun.
This is true even at perigee when its disk will be smaller than the sun's disk even when the sun is farthest from Earth at aphelion. At the current rate that the moon's orbit is increasing, it will take over million years for the last total solar eclipse to occur. A complicating factor is that the size of the sun itself will grow slightly during this time as it evolves as a star, which will act to make the time of "no more total eclipses" a bit sooner than million years.
What happens more often, solar or lunar eclipses? Solar eclipses are fairly numerous, about 2 to 4 per year, but the area on the ground covered by totality is only about 50 miles wide. In any given location on Earth, a total eclipse happens only once every hundred years or so, though for selected locations they can occur as little as a few years apart. An example is the August 21, and April 8, eclipses, which will be viewed at the same spot near Carbondale, Illinois.
Eclipses of the Moon by the Earth's shadow are actually less numerous than solar eclipses; however, each lunar eclipse is visible from over half the Earth. At any given location, you can have up to three lunar eclipses per year, but some years there may be none.
In any one calendar year, the maximum number of eclipses is four solar and three lunar. How well are the ground tracks for solar eclipses known in advance of the event?
The positions of the Sun and Moon are known to better than 1 arc second accuracy. This means that on the Earth, the location of the track of totality is probably known to about 1. Is there a book that shows the solar eclipse tracks going back a few hundred years?
Stephenson and M. Houlden, Cambridge University Press Dover Books, New York. How did total solar eclipses affect civilizations that worshiped the sun?
This tradition apparently goes back a very long time, and may have been started several thousand years ago. We know that Ancient Chinese astrologers were carefully searching for eclipses as far back as BCE. But what of other civilizations such as ancient Egypt and those such as the Incas, Mayas and Aztecs? Amazingly, there are no recorded documents or hieroglyphs that suggest the sudden and unpredicted absence of the sun disks associated with Quetzalcoatl Inca or Ra Egypt was noteworthy in the archeological record.
Part of this, in the case of Egypt, may be due to the fact that most of the eclipse tracks for the period from 2, BDC to BCE, for example, passed over extremely low population density areas in Egypt where there would be very few people to notice the minute dimming of the sun. Perhaps there are records somewhere yet to be translated, discovered, or critically analyzed, that mention such unusual solar events, no doubt witnessed by thousands of people each time in these high-population areas.
Is there any current scientific value for studying eclipses today? During the last century, the precise timing and track of totality could be used to make ultra-precise measurements of the lunar orbit and improve the mathematical model for the gravitational interactions between earth and the moon.
Studies of the solar corona during totality were also used to examine its structure and changes in time, and to relate the features seen with details on the solar surface. Currently, there have been attempts to detect interplanetary dust falling into the sun by searching for its faint infrared light beyond the corona. There are also studies of the solar transition region being performed by the glimpses of it provided during totality.
So new scientific uses for this spectacular phenomenon are found nearly every year! How long does the longest-possible total solar eclipse last? This is about 7.
The longest total solar eclipse from BCE to CE, a span of 12, years, will occur on July 16, and will last 7 minutes 29 seconds. Its path sweeps across Colombia, Venezuela and Guyana. The August 21, total solar eclipse, by comparison, will last a maximum of 2 minutes 43 seconds. How many eclipses are there every year? The statistical distribution of eclipse types for this interval is as follows: 4, partial eclipses, 3, annular eclipses, 3, total eclipses and hybrid eclipses.
That means that, every years you have partial eclipses, annular eclipses, total eclipses and hybrid eclipses. That works out to eclipses of all kinds each year, and about 2 total solar eclipses every 3 years. How many times will a total solar eclipse fall on my birthday? Well…my birthday is November The last total solar eclipse on my birthday was in The next one is in the year , followed by the years and , so the intervals are years, 19 years and years.
So depending on which part of the cycle you are on, you may either wait about 20 years or about years for the next occurrence! Check out the Five Millennium Canon of Eclipses to find the one nearest your birthday. When was the first photograph of a total solar eclipse taken? What is a Saros Cycle? A Saros Cycle is approximately One saros period after an eclipse, the Sun, Earth, and Moon return to approximately the same relative geometry, a near straight line, and a nearly identical eclipse will occur.
The Moon will have the same phase and be at the same node and the same distance from the Earth. In addition, because the saros is close to 18 years in length about 11 days longer , Earth will be nearly the same distance from the sun, and tilted to it in nearly the same orientation same season. Given the date of an eclipse, one saros later a nearly identical eclipse can be predicted. Each total solar eclipse track looks similar to the previous one, but is shifted by degrees westward.
The August 21, total solar eclipse is part of the Saros series. The previous total solar eclipse in this series occurred on August 11, The next one will be on September 2, The first cycle in this series occurred on January 4, , and the last one will be on April 17, How are total solar eclipses used by scientists? Of course the most spectacular use has been to study the faint corona of the sun, which can be observed by spacecraft such as the Solar and Heliospheric Observatory SOHO by making artificial eclipses, but ground-based telescopes and photography have also made many historical contributions to understanding the shape, structure and extent of the corona.
Also, total solar eclipses have been invaluable in improving our understanding of the lunar orbit. Whether a total solar eclipse occurs at a specific location and time on the surface of Earth depends on the lunar orbit, the motion of the moon along the orbit, the earth-moon distance and other factors. Sophisticated physics-based computer models have been used for over a century to make accurate predictions of each eclipse to the second, and to the nearest mile on Earth.
The best way to do this is to look at historical sightings of total solar eclipses from centuries or even millennia in the past. These sightings are often made by observers at specific geographic locations and who indicate the time of the eclipse from that location. These distant-in-time observations can be calculated by the modern eclipse models and compared with the historical sighting, then the models can be adjusted by improving the parameters of the physics calculation until agreement is reached.
For example, in an astronomical event recorded on a clay tablet found in among the ruins of the ancient city of Ugarit, Syria, was identified as a description of a total solar eclipse that occurred on 3 May BCE. The information was used to provide a reference point to establish the long-term evolution of angular momentum in the Earth-Moon system.
What is a syzygy? Apart from being a wonderful word to use in the game of Scrabble, this astronomical term is an event in which one astronomical object is lined-up with another.
This leads to the pithy aphorism: all eclipses are syzygys but not all syzygys are eclipses. For example, Full moon and New Moon are syzygys involving the lining up of the Sun, Earth and Moon, therefore, lunar and solar eclipses are syzygys. When a planetary moon passes across the face of another body but does not eclipse it, this is called a transit. From Earth, the small disks of Venus and Mercury can be seen passing across the face of the sun during transits of Venus and Mercury.
These also involve the straight-line alignment of the Sun, Earth and each planet. On June 3, , the Curiosity rover on Mars observed the planet Mercury transiting the sun, marking the first time a planetary transit has been observed from a celestial body besides Earth.
Previously, the Curiosity rover has captured images of the Martian moons Phobos and Deimos transiting the sun. Will I be able to see sunspots on the sun if I have a telescope and filter? The sun will be well-way from its maximum sunspot numbers during this cycle Number 24 which peaked in with about spots during the peak month. By August, the average number should be about 30 per month. Sunspot minimum will occur sometime in ca if the current trends continue. What this means is that there may be fewer large sunspots, and the ones you see before eclipse will be concentrated near the equatorial zone of the sun.
Is the maximum duration of eclipses changing over time? Totality currently can never last more than 7 min 32 s. This value changes over the millennia and is currently decreasing. By the 8th millennium, the longest theoretically possible total eclipse will be less than 7 min 2 s. When will the next transits of Mercury and Venus occur during a total solar eclipse? The last transits of Venus occurred on June 8, and June 5, , with the next pair predicted for December 10, and December 8, Transits of Mercury are much more common, with the most recent one occurring on May 9, and the next one on November 11, It is not unreasonable to ask when we might expect such transits to occur during the time of a total solar eclipse.
The next anticipated simultaneous occurrence of a solar eclipse and a transit of Mercury will be on July 5, , and a solar eclipse and a transit of Venus is expected on April 5, Does the moon really turn black during a total solar eclipse? If the corona of the sun were not so bright, you would see the moon very faintly illuminated by earthshine.
Our Earth is fully illuminated during the eclipse and it reflects quite a bit of light into space. Some of this lands on the lunar surface and provides a secondary source of illumination.
What is a Saros series? Because synodic months is not identical to anomalistic months or draconic months, The year saros periods do not endlessly repeat. Each series begins with the Moon's shadow crossing Earth near the north or south pole, and subsequent events progress toward the other pole until the Moon's shadow misses Earth and the series ends. A full series from start to finish lasts about 1, years. The August 21, eclipse is part of Saros Series that includes 77 eclipses of which the August eclipse is number All eclipses in this series occur at the ascending node of the lunar orbit.
The series began with the partial solar eclipse of January 4, visible at the North Pole. The series will end with the partial solar eclipse of April 17, visible from the South Pole. The length of this series is 1, years. For this reason, the moon's shadow usually passes either above or below Earth, so a solar eclipse doesn't occur. But as a rule, at least twice each year and sometimes as many as five times in a year , a new moon will align itself in just such a way to eclipse the sun.
That alignment point is called a node. Depending on how closely the new moon approaches a node will determine whether a particular eclipse is central or partial. And these alignments don't happen haphazardly, for after a specific interval of time, an eclipse will repeat itself or return. This interval is known as the Saros cycle and was known as far back as the days of the early Chaldean astronomers some 28 centuries ago.
After this interval, the relative positions of the sun and moon relative to a node are nearly the same as before. That third of a day in the interval causes the path of each eclipse of a series to be displaced in longitude a third of the way around Earth to the west with respect to its predecessor.
For example, on March 29, , a total eclipse swept across parts of western and northern Africa and then across southern Asia. One Saros later, on April 8, , this eclipse will recur, except instead of Africa and Asia, it will track across northern Mexico, the central and eastern United States and the Maritime provinces of Canada.
As a solar eclipse approaches, the mainstream media often will provide a variety of warnings and advisories against looking at the sun with bare eyes, as blindness could ensue. This has given most people the idea that eclipses are dangerous. The sun constantly emits invisible infrared rays that can damage your eyes.
Ordinarily, we have no reason to gaze at the sun. An eclipse gives us a reason, but we shouldn't. By far, the safest way to view a solar eclipse is to construct a "pinhole camera. Binoculars or a good telescope mounted on a tripod can also be used to project a magnified image of the sun onto a white card.
The farther away the card, the larger you can focus the image. Look for sunspots. Notice that the sun appears somewhat darker around its limb or edge. This method of solar viewing is safe so long as you remember not to look through the binoculars or telescope when they are pointed toward the sun; put another way, never look directly at the sun when any part of its blindingly bright surface is visible.
A variation on the pinhole theme is the "pinhole mirror. Open a sun-facing window and place the covered mirror on the sunlit sill so it reflects a disk of light onto the far wall inside. The disk of light is an image of the sun's face. The farther away from the wall is the better; the image will be only 1 inch across for every 9 feet or 3 centimeters for every 3 meters from the mirror. Modeling clay works well to hold the mirror in place.
Experiment with different-sized holes in the paper. Again, a large hole makes the image bright, but fuzzy, and a small one makes it dim but sharp. Darken the room as much as possible.
Be sure to try this out beforehand to make sure the mirror's optical quality is good enough to project a clean, round image. Of course, don't let anyone look at the sun in the mirror. If you're around leafy trees, look at the shadow cast by them during the partial phases. What do you see? Is it worth a photograph? You will see scores of partially eclipsed suns projected through pinhole gaps between the leaves.
This is caused by diffraction, a property of light. According to Vince Huegele, an optical physicist at the NASA Marshall Space Flight Center, the light rays do not shoot straight by the rim of the gaps, or a pinhole, but bend around the edge. This wave effect creates a pattern of rings that resembles a bull's eye. If you want to get all set up for it, we have guides to the best cameras for astrophotography , and the best lenses for astro , so you can be well prepared when the time comes.
Acceptable filters for unaided visual solar observations include aluminized Mylar. Some astronomy dealers carry Mylar filter material specially designed for solar observing. Also acceptable is shade 14 arc-welder's glass, available for just a few dollars at welding supply shops. Unacceptable filters include sunglasses, old color film negatives, black-and-white film that contains no silver, photographic neutral-density filters and polarizing filters.
Although these materials have very low visible-light transmittance levels, they transmit an unacceptably high level of near-infrared radiation that can cause a thermal retinal burn. The fact that the sun appears dim, or that you feel no discomfort when looking at the sun through these types of filters, is no guarantee that your eyes are safe.
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