How is the Earth like a potato?

We often hear about gravity being different on other planets--the Moon is an oft-cited example of how weaker gravity makes you weigh less. But did you know that gravity actually varies on our own planet?

There's this thing called a geoid. It sounds like something out of a sci-fi story, but it's quite real. The geoid is a map of the Earth's gravitational field. And since gravity impacts things like sea level and currents, it's important to understand how it varies.
Welcome home: I think that's South America on the left there...
Welcome home: I think that's South America on the left there...Courtesy ESA/HPF/DLR

Luckily, those crafty Europeans came up with the GOCE (Gravity field and steady-state Ocean Circulation Explorer) satellite, which has painted the clearest picture yet of the geoid. With its variations exaggerated, it makes the Earth look like a giant potato. The variations come from unevenness in earth's mass and shape. Its wobbly surface represents what shape the oceans would take without current, wind, or tide to move them. The satellite also studies ocean circulation and the movement of ice.

This information is particularly important to understanding sea level rise. Scientists predict that, on average, sea level will rise 3 feet overall by 2100. But those three feet will be distributed differently throughout the world, and studying that distribution is pretty complicated. There's the impact of the geoid and of gravity from large ice sheets, but winds and water circulation, water temperature, salinity, meltwater from ice sheets, rainwater runoff, and land changes all leave their marks.
Home sweet tuber: Aww
Home sweet tuber: AwwCourtesy Lumbar

Some of these changes redistribute water (ex. geoid), others add to the volume of seawater (ex. temperature increases), and still others modify the land's height relative to the water (ex. land changes, such as sedimentation and oil extraction). Some changes leave a lasting impact (ex. meltwater from glaciers), while others can vary by the hour or the season (winds).

By developing this most-accurate-to-date geoid and ocean circulation model, researchers have created a picture of sea level at its natural state and modeled some of the processes that alter that state, so that we have a reference point for understanding many of the less-defined factors in sea level rise. And that, my friends, will help us better anticipate and plan for the changes ahead.

Plus it's just kinda cool to see how the Earth is really shaped, huh?

Your Comments, Thoughts, Questions, Ideas

Anonymous's picture
Anonymous says:

i thik the world is not like a patatoe the world is much bigger

posted on Tue, 04/05/2011 - 1:03pm
Witryna's picture
Witryna says:

ha ha I agree with you 110%, it is much much bigger!

posted on Fri, 07/13/2012 - 12:15pm
Shana's picture
Shana says:

The point isn't that the Earth is the same size as a potato--it's that the Earth is a similar shape.

posted on Thu, 04/07/2011 - 4:04pm
JGordon's picture
JGordon says:

No, I'm fairly certain they're about the same size. No need to split hairs here.

posted on Thu, 04/07/2011 - 4:46pm
Juris's picture
Juris says:

That study seems to be very interesting. This whole geoid thing can actually help us better anticipate and plan for the changes ahead. We at Millionaire Mind Intensive Europe (proud that Europeans have came up with this idea) hope that they can come up with final model soon.

posted on Wed, 07/06/2011 - 10:38pm
darrensy's picture
darrensy says:

Through the years, there are frequent changes on the earth, not just the environmental situation but also the physical changes on the earth and it is still on deformation.

posted on Wed, 12/21/2011 - 10:56pm
asim's picture
asim says:

Someone linked this on Twitter with the headline. Radio Stream
I though it was serious until I reached the 'ominously playing with a box of matches', bit.

posted on Sun, 04/01/2012 - 10:01am

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