Thursday, September 29

Potsdam potato: this is the shape the Earth would have if gravity were the same across the entire surface of the planet

Gravity is not the same across the entire surface of the planet. This varies depending on the place, the distribution of the oceans, the mountains and even the time of year. In the end we don’t have to think of the Earth as a perfect, uniform sphere, but as in a rock where the mass is unevenly distributed.

To visualize this effect, scientists from the German Center for Geophysics (GFZ) created what is known as the Potsdam potato, a map that originated in 2005 and later, thanks to different more modern satellites, it was reproduced again in 2011. Here we explain what this particular view of our planet consists of.

The point of least gravity is in India

To better understand how the gravitational field is distributed on Earth, satellites like GRACE and CHAMP helped image our planet based on gravity. The result, instead of being a sphere, is a geoide. It is about the body that is precisely defined as one where all the points on its surface have the same gravity.

It is known that there is a greater flattening at the poles, but thanks to these observations of the center of Potsdam it was possible to have a more precise map, where the Continent masses, water balance, snowmelt, and climate-related variables. It is a model that not only helps to better visualize the Earth in an instant, but also allows us to evaluate changes over time. Today, these gravity maps are very accurate and are commonly used to carry out all kinds of investigations and calculations.

The image that illustrates this article is the Model EIGEN-6C, better known as the original Potsdam potato from 2005, where the red colors indicate the regions with more gravity and the blue ones with less.

In the previous image we see a similar result, but with up to four times the resolution. This is the image that ESA provided in 2011. Most dents and valleys can be attributed to mountains such as the Himalayas or to landforms like the Mid-Atlantic Ridge.

Specifically, we can note that the region with less gravity on Earth is located in southern India. Also in the North American region there is a low gravitational field.

New Goce Geoid

Same geoid as ESA, but focusing on other regions.

If we look at Spain, we see that we are in a yellow zone turning red, which indicates a high gravitational field. Both northern Europe and the western part of South America corresponding to the Andes have a zone of high gravity. Like Australia.

Thanks to the LAGEOS, GRACE and GOCE satellites of the European Space Agency (ESA), gravity measurements, with high precision and in hard-to-reach areas as for example in Central Africa or the Himalayas.

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