Imagine if all of the Earth topography, mountains and valleys were scoured off leaving a continuous world's ocean completely at rest, without the effects of currents, weather and tides. The effect of the Earth's gravity on this hypothetical world mean sea level is represented by the geoid. However, because the Earth's gravity is not equal in all places, this hypothetical ocean is not perfectly smooth. The strength of the Earths' gravity, and consequent effect on the shape of the geoid is represented by color variations in this image. Click on the image to see another example.