Earth is a perfect sphere, right? The images from space and the globes in our classrooms make it seem so. But the shape of our planet, though it appears so solid and spherical from space, is, in reality, more potato than perfect.
The European Space Agency’s GOCE (Gravity Field and Steady-State Ocean Circulation Explorer) mission is one of the missions that focused on mapping Earth’s gravity and providing data to give us a clearer picture of Earth’s shape. Combined with other data collected by NASA missions, the results show that it is definitely not flat, but it’s not perfectly spherical either.
It does indeed look like a potato. Here’s why.
Read More: Aristotle Discovered the World Is Round – One of the First Important Scientific Theories
A Lumpy and Irregular Surface
Our planet’s surface is pretty lumpy and irregular. For starters, the planet is slightly fatter at the equator due to the force of the Earth’s rotation, which pushes Earth’s surface out slightly. But at a more granular level, mountains, hills, valleys, and lush plains cover the planet.
As a dense mountain has more mass than a valley, gravity will act differently across the planet. Where the planet is denser, gravity will be fractionally stronger, exerting a greater pull.
This pull has noticeable effects on Earth’s surface, specifically on its liquid component — our seas and oceans. The pull of our moon and sun also yanks on these waters, causing tides. But as the National Ocean Service frames it, if we could remove the tides from the oceans, the ocean surface would become a smooth, irregular surface. Areas with higher gravity would pull water in, raising the level of this hypothetical tideless sea. Where gravity is low, the sea level would also be lower.
Earth is Geoid-Shaped
Scientists who study our planet go a step further in their modeling. They extend this imaginary sea level all across the planet’s surface, reflecting the differences in gravity’s strength across land, too. This produces a shape called the geoid, which reflects how gravity warps Earth’s surface, according to NASA. The geoid is pretty ugly to look at.
This depiction of the geoid is greatly exaggerated — the differences in height have been multiplied by 10,000 times. In reality, the difference between the highest and lowest points on the geoid is about 656 feet (200 meters). The geoid’s “peak” is found at 278 feet (+85 meters) in Iceland, whereas its lowest level is in the Indian Ocean, at -347 feet ( -106 meters).
How GOCO Maps Earth’s Gravity
Gravity in this latter region is the weakest it is on Earth, across an area roughly the size of India itself. Researchers think that the formation and arrangement of structures deep within Earth’s mantle have contributed to this gravity anomaly, but its true origin is still unclear, according to a study in Geophysical Research Letters.
The geoid is useful to scientists who want to calculate exact surface elevations across the planet and is computed by powerful gravity field models, such as GOCO06s, which is derived from satellites linked to the GOCO (Gravity Observation Combination) project, according to NASA. GOCO has built its model using 15 years of data from 19 different satellites, which have together assembled more than a billion observations of Earth’s surface.
The geoid, lumps and all, represents a truer “shape” of the Earth than a simple sphere. Like many events happening on it, our planet’s surface is messier than it might first appear.
Read More: The Earth Is Round, and Is Also a Shifting, Squashed Spheroid
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- This article references information from the ESA: GOCE
- This article references information from the ESA: New GOCE geoid
- This article references information from the National Ocean Service: What is the geoid?
- This article references information from NASA: The Geoid
- This article references information from a study published inGeophysical Research Letters:How the Indian Ocean Geoid Low Was Formed