Viewing a Solar Eclipse: What It Is, and When You Can See OnePublished on April 3rd, 2015 | by ttn in Astronomy
We are used to the consistent cycle of day and night as a species. We expect cloudy days and the occasional fog, but otherwise the cycle continues unabated. Every so often though, we experience a solar eclipse that changes day to night in a matter of minutes.
This is especially true in a total eclipse which is a rare and breathtaking sight. While this special kinds of eclipses only occur every so many years and in specific regions, we’ll help you know when it’s time to step outside and how you can view one of these spectacular events.
An Overview of These Events
From our place on Earth, this type of eclipse occurs when the moon moves between the Sun and the Earth. If certain factors are met, the sun’s light will be partially or totally blocked. This can only occur during a new moon and when an alignment is achieved between the Sun, Earth and moon which known as a syzygy.
The moon’s orbit is not perfectly circular though, which is why these events are rare, the total versions being the rarest of all. If the moon’s orbit was circular and it moved in the same orbital plane as Earth, we would see a total eclipse every month. Since the moon’s orbit is tilted by about five degrees though, the shadow a new moon casts is rarely projected onto the Earth.
On top of this, the moon’s orbit carries it too far away from the Earth to fully block the sun’s light from our perspective. These orbits do tend to cross during each revolution at lines of nodes. This creates between two and five eclipses per year, two of which could potentially be total in nature.
A total eclipse is not viewable by the entire planet though, the totality is only viewable on a small piece of Earth’s surface during these events. These events are natural, though ancient cultures have been known to attribute them to supernatural causes or bad omens. For those who did not have a grasp of a total eclipse’s astronomical nature, the sudden change from day to night momentarily was frightening.
We will go into more detail further into the article, but it is worth noting that these events should not be viewed with the naked eye. While there are experts known as “eclipse chasers” and “umbraphiles” who view the event during its totality phase, most people won’t know when this occurs.
Indirect viewing techniques and eye protection are required to safely view one of these occurrences. Let us find out when the next eclipses are supposed to take place and when we can expect a total event in the near future.
Upcoming Total Solar Eclipse Events
Knowing the time and date of a total eclipse is not enough. Because the moon’s shadow, or umbra, is only a few hundred kilometers wide, the viewing area for a total eclipse on the Earth is small and it happens quickly. On average, a single place on Earth will only see a total eclipse once every 360 years.
The next total eclipse will occur on March 20, 2015. This eclipse will only be viewable across the high Arctic region of the world. Specifically it will be viewable in Iceland, Europe, other northern regions of the world.
After this, the next total eclipse will occur on March 9th, 2016 over Southeast Asia. Finally, there is to be another one over the United States on August 21st, 2017. The path of totality is across the central portion of the continent.
These events go through several distinct stages before the eclipse is complete. The longest totality in the 21st century occurred on July 22, 2009 and lasted for six minutes and thirty-nine seconds. Normally totality lasts between a couple seconds and seven minutes.
On the grand scale of time, eclipses like these are only possible for a small amount of time. We are able to see total eclipses because a very specific set of factors are in place. Millions of years ago, the moon was too close to the Earth to cause this type of phenomenon.
A billion years from now, these events will no longer occur as the moon will be too far away for the circumstances to be possible. Tidal acceleration causes the moon’s orbit to become 2.2 cm more distant each year. By this logic, the last total eclipse will occur on Earth roughly six hundred million years from now, and the event will never occur again.
A total eclipse goes through five stages and overall lasts several hours before it’s complete. The stages are as follows:
- Partial Eclipse – Also known as first contact, this stage occurs when the moon’s shadow slowly begins to move over the Sun’s disc. Here it looks like the Sun is missing a chunk of its shape.
- Full Eclipse Beginning – This is known as second contact and occurs when the moon covers almost the entirety of the sun. Those who are in the moon’s umbra will see Baily’s Beads and the diamond ring effect.
- Maximum Totality – The moon covers the entirety of the Sun. Only the corona of the star is visible at this point. The sky darkens, temperatures drop, and animals are silent since they think it is night.
- Full Eclipse Ending – Also known as third contact, this is when the moon’s shadow begins to to move away and the Sun’s light reappears.
- Partial Eclipse Ending – This is referred to as fourth contact and represents the moment when the moon ceases to overlap the Sun and the eclipse ends.
How to Properly View an Eclipse
Looking directly into the photosphere of the Sun can cause permanent eye damage to the retina. The Sun’s light emits both intense visual light and radiation that can cause your vision to become impaired or even blind you. There are no pain sensors in the retina, so you may not notice damage for several hours if you were to look at the sun.
Normally the Sun is too bright to look at directly, but people are often tempted to look when the eclipse begins and the Sun is less bright. It is still just as dangerous to look directly at it, unless the event is in it’s totality stage. Even if you’re using a visual aid like a telescope or a pair of binoculars, you can still permanently damage your eyes within a fraction of a second.
Luckily there are methods of viewing eclipses that are total, annular, or partial. These methods are detailed below:
- Pinhole Projection – This is the safest method as it is indirect in nature. It allows you to create a simple and cheap device that projects the sun’s image onto a sheet of paper or cardboard using a small looking device like a pair of binoculars or a telescope.
- Eclipse Glasses – While regular sunglasses will not protect your eyes during an eclipse, you can find specialized solar lenses that will allow you to view the event safely.
- Welder’s Goggles – NASA states that these must be above a 14 rating to properly work safely.
As a final piece of advice, be sure not to use any of the following items as viewing devices:
- Medical X-ray images
- Smoke Glass
- Sunglasses of any type
- CD or floppy disks
None of the above items will protect you and could cause eye damage. When it comes to solar eclipses, remember to be safe and enjoy these unique and breathtaking events as they only occur in specific places each time.