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Solar Eclipse Frequently Asked Questions (FAQ)

Do you have questions about solar eclipses? Who doesn't! Chances are we have answers to most of your questions here.

What is a total solar eclipse?

A solar eclipse is an astronomical event in which the Moon passes directly between the Sun and the Earth, blocking out the light from the Sun for a short period of time. This causes temporary darkness, allowing viewers to look up at the eclipse (using proper equipment) and giving observers the unique opportunity to view the Sun’s solar corona. Additionally, viewers can see surrounding stars and planets during this momentary darkness as animals transition to their nocturnal behaviors. Although solar eclipses happen every year (up to five times), celestial mechanics makes witnessing one from your exact location a much anticipated event. If you are located directly in the Moon’s shadow, you will momentarily experience complete darkness, known as a total solar eclipse. If you are in a location where the light is not completely blocked by the moon, then you will experience a partial eclipse. 

What is difference between a solar eclipse and an eclipse of the Sun? 

Although these two terms are both used, they are simply used interchangeably.
A solar eclipse describes the actual event, as the term “eclipse of the Sun” is used more towards describing what is happening during the event. 

Isn't the Sun larger than the Moon, so how does this work?

The Sun and the Moon appear to be the same size during an eclipse. As you might have guessed, in reality, the Sun is much larger than the Moon. In fact, the Sun’s diameter is 1.3914 million km and the Moon’s diameter is 3,474 km. That means the Sun’s diameter is roughly 400 times larger than that of the Moon! The reason they appear to be the same size during an eclipse is because of their relative distance from the Earth. Coincidently, the Sun is also roughly 400 times farther away from the Earth than the Moon, making the two celestial objects appear to be the same size! 

What do the terms magnitude and obscuration mean?

Astronomers use two defining factors to categorize solar eclipses: their magnitude and obscuration. In astronomy, there are two ways the term “magnitude” is used. First, the magnitude of a stellar object describes either it’s apparent or absolute brightness. For example, if you were to go outside and look up at the sky and compare the brightness of two different objects, whichever one appeared to be brighter would have a lower magnitude. Although this may seem strange, the lower the magnitude, the brighter the object.

Alternatively, the magnitude of a solar eclipse describes the percent value of the Sun’s diameter that is covered by the Moon during the eclipse maximum. Keep in mind, this describes the ratio of diameters of the two objects, not a measure of the Sun’s surface area covered by the moon - this would actually be obscuration!

Obscuration is actually the fraction of the Sun’s surface area that is occulted by the Moon when the eclipse is at its maximum. 

Is it true that the closer you are to the center of the path of totality, the longer totality will be for you?

This is absolutely true! If you’d like to witness the total solar eclipse but would like to be able to experience totality for as long as possible, you should travel to a location that falls as close as possible to the center of the path. 

Are total solar eclipses only visible from Earth?

Eclipses can happen anywhere there is a three body system involving a star, planet, and moon. More specifically, the angular size of the star has to match the angular size of the moon passing in front of it. If the moon passing in front of the star is too small, we would simply see it pass in front, or transit, but it would not effectively block out the light from the star. For example, when we have the opportunity to witness Mercury passing in front of the Sun, as we did in 2016, we were only able to see a small, dark object “slowly” pass in front of the disk of the Sun.
Additionally, when the disk of the moon passing in front of the star is much larger, it can also be considered an eclipse. For example, when the Earth passes in front of the Sun and casts a shadow on the Moon, the Moon will experience a lunar eclipse. From Earth, we see the Moon turn an interesting orange color caused from light from the Sun passing through Earth’s atmosphere. But, if you were actually on the Moon during a lunar eclipse, you would see the light from the Sun blocked out, similar to a solar eclipse. The only difference is, the Earth would be too large to allow viewers on the Moon to see the Sun’s solar corona - a factor that is included when viewing a solar eclipse from Earth.   

Does the moon really turn black during a total solar eclipse?

It is not the moon that turns black, but simply the fact that the light from the Sun is being blocked by the Moon. If the solar corona wasn’t as bright, you would actually be able to see the moon faintly illuminated by the light reflected off the Earth’s surface. 

When do solar eclipses occur?

A solar eclipse happens when a New Moon passes at just the right angle between the Earth and the Sun, casting a shadow on the surface of the Earth.
Because the Sun and Moon have the same angular diameter when viewed from Earth, the Moon appears to be the same size at the Sun’s disk, therefore, the Moon effectively blocks out the light from the Sun. If you are located on Earth in a place where the Sun appears to be completely blocked, you will experience a total solar eclipse. If you are at an angle in which only part of the Sun is blocked, you will see a partial eclipse. 

Why is it still not safe to look at the Sun even when only a small part of it is visible?

As you probably know, the sun is very dangerous to look at. What you might not know is that even when there is just a very thin slice of the Sun’s disk visible, the light sensitive rods and cones in the human retina can be harmed. In the daylight, your iris naturally contracts, limiting the amount of light that passes through. This makes daylight perfectly safe to see. However, if you gaze directly at even the smallest area of the Sun, the light will damage these individual retinal cells. If you’ve ever done this on accident, you may recall seeing bright spots as you glance away. Now, if these cells were not too harshly damaged, these spots will go away. Unfortunately, if you looked at the Sun for too long, this damage can be permanent. One very important warning is that you should never assume that quickly glancing at the Sun will keep you from causing harm to your eye. Everyone's retinal sensitivities are different and you never know how long it will take to cause your eyes irreversible damage. If you would like to look directly at the Sun, use proper solar filters or “eclipse glasses” allowing you to see interesting features on the surface instead of a bright blinding blob! 

Why don't solar eclipses happen at every New Moon?

Although it would totally be possible for an eclipse to happen during successive New Moon’s, the Moon’s orbit is actually tilted 5° relative to Earth’s orbit. When the two orbits are perfectly aligned, astronomers refer to these points as nodes. At one node, when it is a New Moon, a solar eclipse is possible. When it is a Full Moon, there can be a lunar eclipse. But because of the relative angle in relation to the Sun, there is still only an eclipse when all three objects lie within the correct alignment.

How are eyes damaged by looking at the Sun?

Looking directly at the Sun, even for just a few seconds, can result in blurred vision, visible light and dark spots, increased light sensitivity, or vision loss in the center of the eye, also known as the fovea. This is called solar retinopathy, a consequence of excessive ultraviolet light flooding the retina. Looking at the Sun for roughly 100 seconds can cause permanent retinal damage, although the amount of time varies by the individual, how much the pupil is dilated, and how intense the light from the Sun is at that given moment. What is most interesting is that the eyes do not have pain receptors in the retina, meaning your retina can be damaged before you’ve even realized it.

Why do some eclipses last longer than others?

There are many factors that contribute to the length of time an eclipse lasts. For example, since orbits are elliptical, the Earth is not always the same distance from the Sun and the Moon is not always the same distance from the Earth. The distance between the Earth and the Sun can vary by 3 percent while the distance between the Earth and the Moon can vary by 12 percent. Because of this, the apparent angular of the Moon can range from being 10 percent smaller than the Sun to 7 percent larger.

Aren’t solar eclipses pretty common?

In general, eclipses are actually pretty common! At most, there can be 7 eclipses in a single year - 5 solar eclipses and 2 lunar. Alternatively, it could also be 4 solar eclipses and 3 lunar. However, to be able to witness a total eclipse, you must be within the path of totality. It is this reason that makes total solar eclipses so unique! Although they happen quite often, the 2017 total solar eclipse will be the first to happen over the US for the first time since 1979, 38 years ago! Additionally, partial eclipses are nowhere near as interesting since an eclipse is not noticeable until the Sun is more than 90 percent covered by the Moon.

When will the next total solar eclipse occur in the US?

After August 21, 2017’s total solar eclipse, the next visible eclipse over the US will be April 8th, 2024.

Wasn't there just an eclipse of the Sun in the U.S. not too many years ago?

There was a total solar eclipse on March 7th, 1970 that passed up the east coast of the United States. Additionally, there was solar eclipse in 1979 that only few were able to see as it passed over just five states in the northwest. There was also an eclipse in 1991 that only observers in Hawaii could see.
But it’s not the frequency of eclipse that makes them so special, it’s your rare opportunity to see one first hand! As you’ll hopefully get to see for yourself, no photo, video or diagram can truly capture just how incredible these events are. There is something truly captivating about these short lived events that no partial eclipse, annular eclipse, or image could ever hold a torch to. 

Do lunar and solar eclipses have any noticeable effect on humans?

Although we have not found that eclipses have any physical effects on humans, there is a long history of psychological correlations. As the Sun’s light is blocked out by the moon, many civilizations have interpreted the event as being a symbol of doom - initiating even human sacrifices. 

When is it possible for a solar eclipse to occur?

When a New Moon passes at the perfect angle between the Earth and the Sun. When this happens, the Moon casts a shadow on the surface of the Earth. If you happen to be in a location where you are within this shadow, then you will witness an eclipse of the Sun. 

During the total solar eclipse in 2017, how long will totally last?

Although the length of totality depends on your location, totally is expected to last a maximum of 2 minutes and 40.2 seconds in Giant City State Park, just south of Carbondale, Illinois. This location will experience the longest duration of totality. 

Can two consecutive New Moons can each give rise to a solar eclipse?

Yes, both are possible! Even though they cannot both be total solar eclipses, two different kinds of eclipses are totally possible. 

Why are eclipse totalities different lengths?

They are different because Earth is not always at the same distance from the Sun and the Moon is not always the same distance from Earth.

Will you experience a temperature drop during a total solar eclipse? 

When the Sun is fully blocked, you can expect to feel a temperature drop of about 10-15°F. 

What is the solar corona?

The solar corona is the visible outer atmosphere of the Sun. Although it is typically hidden by the brightness of the Sun, when the eclipse reaches totality, the corona is suddenly visible. 

Will there be any planets visible during the eclipse?

During the 2017 eclipse, at about 80% coverage, Venus will be visible just 34° west-northwest of the Sun.

Does a total solar eclipse affect the wildlife in the area?

Many animals change to their nocturnal behavior as the light dissipates.For example, many birds are known to stop chirping. Additionally, bats and owls may become more alert as farm animals prepare to fall asleep. You may even hear grasshoppers begin to make their characteristic sound. 

Can you see anything when the Sun is completely eclipsed?

When the Sun is completely covered by the Moon during totality, observers will get the rare opportunity to view the solar corona. The corona is the outermost layer of gas that makes up the Sun’s atmosphere. It is typically masked by the light emitted by the Sun’s surface, but during a solar eclipse, the majority of the light is blocked out, making the gasses contained within the corona visible around the edges of the Sun. 

In regards to the 2017 total solar eclipse, how wide is the path of totality?

In accordance to path of totality, there is roughly a 70 mile wide path that observers can witness complete totality.

How many different types of eclipses are there?

There are four types of solar eclipses:

Total Eclipse: When the Moon completely covers the solar disk.
Annular Eclipse: When the Moon is too far away from the Earth to completely cover the Sun, you will see a dark center surrounded by a bright ring around the Moon.
Partial Eclipse: A partial eclipse happens when you are observing an eclipse within the Moon’s penumbra, the lightest part of its shadow. An observer will only see part of the Sun’s disk covered.
Hybrid Eclipse: A hybrid eclipse has characteristics of both an annular and a total eclipse, depending on your location on Earth and the Earth - Moon distance. 

Why does the Sun and the Moon appear to be the same size?

The Sun’s diameter is approximately 400 times larger than that of the Moon. The Sun also lies roughly 400 times farther away, meaning both objects appear to be the same size.

What does the magnitude of a solar eclipse mean?

The magnitude of a solar eclipse is the fraction of the Sun’s diameter that is covered by the moon when the eclipse is at its maximum coverage. Keep in mind, this describes the ratio of diameters of the two objects, not a measure of the Sun’s surface area covered by the moon.

What is the obscuration of a solar eclipse?

Obscuration is the fraction of the Sun’s surface area that is covered by the Moon at the eclipse’s maximum. Eclipse obscuration may be expressed as either a percentage or a decimal fraction. 

When is the only time you can look directly at the Sun without the use of equipment?

Never! You should never look directly at the Sun when it is visible. However, during totality, when the Moon has completely eclipsed the Sun and it is no longer visible, you can look directly at the eclipse. This is an amazing opportunity to see the Sun’s solar corona - the outer layer of the Sun’s atmosphere which is otherwise not visible because of the overwhelming brightness of the Sun! 

Is there a difference between a solar eclipse and an eclipse of the Sun?

No, they are referred to as the same thing and both terms can be used interchangeably. 

Why doesn’t an eclipse happen every month during a New Moon?

The Moon’s orbit tilts 5° relative to Earth’s orbit. Therefore, if the Moon is not at the correct angle, it will not appear to cover the disk of the Sun. 

Where do I need to be to watch the eclipse?

The path of totality is the path in which observers will see totality during the eclipse.
For the 2017 eclipse, the path of totality is about 70 miles wide stretching from Oregon to South Carolina. Wiewers will want to be located along this centerline if they want to experience the longest duration of totality possible. 

Typically, how big of a temperature drop do you experience during a total solar eclipse?

As the eclipse progresses and light dissipates, you will notice a significant temperature drop. The Sun produces electromagnetic radiation energy of about 1,000 Watts per square meter. When this radiation is blocked at the moment of eclipse, there is a very quick temperature decrease. This can be a drop of 10-15°F leading up to totality! If the wind is blowing, this temperature drop will feel even more significant. 

What are "shadow bands?"

While totality slowly approaches, an interesting phenomenon can be seen both before and after the total eclipse. If you were to place a white sheet of paper on the ground, you would see be able to see shadow bands that look like ripples of sunshine at the bottom of a swimming pool. More specifically, light from nearby large objects are split into interfering patterns that appear as alternating lines of light and dark bands that appear to be wiggling. This event is caused by refraction of the Moon’s shadow passing through the atmosphere.

Why don't solar eclipses occur exactly at noon?

A total solar eclipse is not solely dependent on the location of the Sun. The time of day that the eclipse happens depends on the relative locations of the Earth, Sun, and Moon. As the Moon passes in front of the Sun and traces a shadow on the surface of the Earth, the time that the eclipse happens for a specific observer depends on your location when the shadow passes over you. 

If you are not in the path of totality, what will you see?

If you are not in the path of totality, you will only experience a partial eclipse. This means, instead of seeing the Sun’s disk being completely covered by the Moon, observers will only see part of the face of the Sun covered. This is significantly less interesting since an eclipse is not noticeable until the Sun is more than 90 percent covered by the Moon.

Is there a chance that the predicted timings of a solar eclipse will be different during the actual event?

We have become extremely accurate when it comes to calculating the motions of the Sun, Moon, and Earth. Therefore, we are very confident in our predicted times.  

I’m really close to the path of totality. Will I see anything interesting from where I am?

If you are close to the path of totality, it is completely worth it to make the drive to a location where you are within the path. If you are not within the path, you will only see a completely anticlimactic partial solar eclipse. These types of eclipses are common and quite honestly, uninteresting. To experience any of the incredible effects of a total solar eclipse, you have to be located within the path of the totality for it to be worth it. Keep in mind, no photographs, videos or any other media will do it justice. Witnessing totality with your own eyes is the only true experience. 

What if it’s cloudy that day?

For anyone that’s excited to see an eclipse, the thought of cloudy weather can be pretty detrimental. Unfortunately, there’s one simple answer to the question: If it’s cloudy, you won’t see a thing. Regardless of how advanced our prediction methods are, we still can’t change the weather. For the serious eclipse chasers, they choose locations that have a record of low cloud possibility. Some may even have a small plane nearby ready to jet off if weather isn’t permitting. Many of those committed on this level have no problem flying to even the most remote places just to see full totality. Once you’ve seen it, you’ll understand why they get so addicted to these incredible moments. 

Do scientists still study eclipses today?

Solar eclipses provide a unique opportunity for scientists to study a wide variety of topics. Actually, it was during the 1919 total solar eclipse that Einstein was able to study his theory of General Relativity! More recently, studies of the solar corona still exist in order to examine the corona’s structure, variation over time, and unique features on the solar surface. Additionally, studies of infrared light have contributed to scientific studies of interplanetary dust falling into the Sun. In essence, although there are varying specifics to be learned about the Sun, the precise mechanics of eclipses have allowed scientists to accurately predict the timing and path of totality as a result of the lunar orbit and studies of gravitational interactions. 

Do solar eclipses effect Green Power generation?

On March 20, 2015, there was a solar eclipse that reduced solar power production by nearly 38% as compared to a typical clear sky day. Additionally, as temperatures decrease during a solar eclipse, wind is also reduced. This impacted wind farms as wind turbine production decreased. 

Are there any gravitational effects on observers during a total solar eclipse?

The gravitational effects during a total solar eclipse can be broken down using Newton’s Law of Gravity to calculate the forces of the Sun, Moon, and Earth. As detailed by NASA’s website, during the August 21, 2017 eclipse, Earth will be 151.4 million kilometers from the sun, and the moon will be 365,649 km from the Earth. If we calculate each of these forces on a grounded 80 kg person we find: The Earth contributes 784.1 Newtons of force (176.42 pounds), the moon provides 0.0029 Newtons (0.01 ounces) and the sun provides 0.4633 Newtons (1.6 ounces). We must also account for the earth’s rotational centrifugal force. Summing the forces, we get a total gravitational force of 783.634 Newtons or 176.317 pounds. This means that during the total solar eclipse, you will be about 1.7 ounces lighter!

Can’t I just watch the whole thing on TV?

Yeah, sure, you definitely could. Just like you can flick on your television during New Year's and watch the ball drop in New York. Yeah, its pretty and all. It’s fun to watch.. But imagine how much more exciting it would have been to actually be standing in Times Square, chanting out the countdown in a crowd of people and watching the clock strike midnight! An incredible experience that blows watching it on TV out of the water. The same thing can be said about watching a total solar eclipse. You can see every image, watch all the videos, everything, but nothing will ever compare to the real thing. Trust us, seeing totality with your own eyes is worth the fuss. It’s an event you’ll talk about for the rest of your life!

How long is totality?

During the 2017 eclipse, totality will last a maximum of 2 minutes and 40.2 seconds. Although, to experience this maximum duration, you’ll need to be located slightly south of Carbondale, Illinois, in Giant City State Park. Keep in mind, there will tons of people there because of this fact, so if you plan to visit this site, get there as early as possible! If you’re wondering how long totality will be in your location, refer to an online eclipse map.