Solar Eclipse FAQ with National Geographic Expert Aurora Elmore

How is it that the moon appears to be exactly the same size as the sun, when both are observed from Earth? 

Objects that are closer to you appear to be larger. In the case of an eclipse, the sun is about 400 times larger than the moon, but the sun is also about 400 times further away, so they appear to be roughly the same size to us. So from our perspective, because the moon appears to be exactly the same size as the sun, it apparently covers the sun almost perfectly during a full eclipse, turning day into night for a few minutes along the Path of Totality.

What is the ‘Path of Totality’? 

The ‘Path of Totality’ is the region of the Earth where you can view a total solar eclipse (when the sun appears 100 percent covered by moon). The Path is about 60 miles wide and will track from Oregon to South Carolina across the continental United States.

What will I see during this eclipse? 
If you are lucky enough to be on the Path of Totality, then you should experience a total eclipse where the moon completely covers the sun. Just before the sun is entirely obscured, you will see a ring of bright light around the dark moon. The further away you are from the Path of Totality, the less complete your eclipse will appear. For example, at National Geographic Headquarters (in Washington, D.C.), the moon will cover a maximum of 81 percent of the sun. 

How will it feel during the eclipse? 
The eclipse will be at a maximum for only a few minutes. The temperature will drop slightly and the sky will darken slightly, as if a large cloud is covering the sun. Some animals ­— especially birds — may change their behavior. 

Why is this solar eclipse significant? 
This is the first time a Path of Totality will go from coast to coast of the U.S. since 1918. The next time a total eclipse will cross the U.S. will be on August 12, 2045.  

Why are scientists so interested in this total eclipse? 

An eclipse is one of the only times when scientists can make accurate measurements of the sun’s corona, its outer atmosphere. Scientists have an easier time making these measurements when the eclipse is visible over land. In this case, the eclipse will occur over land for almost an hour and a half. That’s enough time for a lot of measurements! Check out some of NASA’s plans for the eclipse here

How has the National Geographic Society funded research of the solar eclipse? 

In our 129-year history, the National Geographic Society has supported numerous astronomical research projects. One of our repeat astronomy grantees is Jay Pasachoff, who has been working to educate adults and children about the upcoming eclipse.

Why is it important to wear the authorized glasses to view the eclipse? 
Do not look directly at the sun without special glasses, even when it is partially covered by the moon. You can seriously damage your vision. 

Fun Fact: How old is the moon? 
Geologists estimate the moon to have broken away from Earth 4.53 billion years ago. 

Dr. Aurora Elmore is the National Geographic Society’s Resident Geologist and Senior Program Officer for Our Changing Planet grants. Learn more about the Society’s grants program.

Changing Planet

Meet the Author
Dr. Aurora Elmore is a geologist, climate change expert and Program Officer for the "Our Changing Planet" grant program at the National Geographic Society. She received her Ph.D. in Geology with a focus on oceanic chemistry and deep-sea circulation and then worked as a researcher at several American and British universities before coming to National Geographic.