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Round? Flat? Science says Earth is neither

The Earth is not a perfect sphere. It is slightly squashed at the poles and a bit wider at the equator.

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The Earth is not a perfect sphere
By
Tony Rice
The Flat Earth International Conference is this Thursday and Friday at the Embassy Suites Hotel in Cary. Presented by Krptoz, an Edmonton, Alberta, Canada-based marketing company, this is the conference’s first year.

According to the website, the conference focuses on “dissent from the spinning heliocentric theory of cosmology … We maintain that the earth is flat and stationary.” Tickets are sold out according to the official website, but streaming video packages are also available.

Looking over the conference agenda, they did get one point right: the Earth is not round.

It's an oblate spheroid.

An oblate spheroid is a sphere slightly squashed at the poles and a bit wider at the equator. The difference in diameters measured at the poles and at the equator is very slight, only about 26 miles. Think of it this way: standing on the equator, you are about 13 miles further from the center of the Earth than someone standing at one of the poles.

Oblateness is caused by rotational forces and the tendency to redistribute the oceans and even the body of the planet itself along the equator. The greater the rotational force and the more fluid the planet (including its atmosphere, oceans and body), the more oblate the planet.

This difference isn't apparent. Looking at full disk images produced by weather satellites or NASA missions, the Earth looks quite round. Though look closely at images larger than 5000x5000 pixels and you’ll find it occupies a pixel or more of the image side to side than it does top to bottom.

Measure these images straight from NOAA weather satellites and you'll come up with ratios very close to the 0.99665 ratio of the equator to the poles. This number is used in a variety of calculations to adjust the force of gravity based on latitude as well as determining satellite orbits.

Scientists have been observing that bulge, noting that it has been reducing at a rate of about one quarter inch each year. This is mostly due to recovery from the last ice age which ended only about 12,000 years ago and the massive ice sheets covering most of the Earth's surface.

Recently, using data from NASA’s Gravity Recovery and Climate Experiment (GRACE) satellites, Robert Nere and John Wahr found reduction of the bulge had slowed and recently stopped. The "dominant contributor” is ice loss, primarily from Greenland and Antartica. The infusion of water from melted polar ice goes straight to Earth’s waistline.

The North Carolina coast from Albemarle to Wilmington is visible from this unmanned amateur balloon. (Credit: NC Near Space)

You can observe the Earth’s roundness yourself.

My favorite way is during a lunar eclipse. The round shadow cast onto the lunar surface comes from our very round Earth. You can next see this during the total lunar eclipse on Jan. 31, 2018.

We can also look to the shape other planets of our solar system as a demonstration of how ours works. With a moderately sized telescope and a few hours of observing you can watch Mars or Jupiter rotate. Jupiter has even higher oblateness of 0.99352 which creates an extra 5,764 miles of diameter at the equator.

If you don’t have a telescope, mark your calendar for Morehead Planetarium Skywatching on Dec. 13. Free and open to the public, the event is made possible by area astronomy clubs volunteers who share their telescopes and know-how.

High altitude pilots and even passengers on the Concorde report the curvature of the Earth is “plainly visible” from their window seats.

Closer to home, NC Near Space captures some incredible images from even higher altitudes. The higher the balloon makes it before bursting, the more evident Earth’s curvature is in photos.

A recent flight launched from Yadkinville, NC, reached 132,000 feet before the balloon burst, producing incredible views from Charleston, SC, to Roanoke, VA, and on across the Appalachians. The curvature of the Earth is clearly visible in these images.

The Greensboro area is visible near the center then the Appalachians leading toward the curving edge of the horizon and thin atmosphere. (credit: NC Near Space)
Tony Rice is a volunteer in the NASA/JPL Solar System Ambassador program and software engineer at Cisco Systems. You can follow him on twitter @rtphokie.

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