The most common question we get is "How do you know that's what the earth really looked like?". We'll explain how we make our images, and show you a real image of the earth so you can see for yourself.
Geostationary satellites orbit the equator at about 22,000 miles above the surface. At this altitude, they orbit once per day, at the same rate that the earth turns. This means that they always stay above the same spot on the equator. This makes geostationary satellites great for things like weather monitoring and communications, since they stay in a fixed location relative to a point on the ground. If you have a satellite dish at home, it's pointed towards a geostationary satellite.We use cloud images from five geostationary weather satellites:
We download the latest images every three hours from the Dundee Satellite Receiving Station and combine them to create a cloud map covering the whole world. It's impossible to make a global cloud map using visible light, since it's always night over half of the world, so we use infrared images, which can be taken during day or night. This way our cloud maps can cover the whole world, not just the part that is sunlit! It's not exactly what your eye would see, but it makes a pretty good "snapshot" of the cloud patterns all around the world at any given time.
When you choose a date and time, the corresponding cloud map is combined with daytime and nighttime maps (from NASA's monthly Blue Marble images) to create a global map:
Finally, given your location, this global map is wrapped around a sphere and oriented as you requested. The effects of Rayleigh scattering are included to give the Earth its familiar blue color.
But still, is this how the world really looked?
It's surprisingly hard to find a color image of the earth with enough detail to see the continents, but here's a good one. This is a real image of the earth, taken from the MESSENGER spacecraft as it flew by on its way to Mercury on August 2, 2005, next to an image we created for the same date and time, seen from MESSENGER's location:
Our cloud map archive has images every three to six hours going from January 2002 to the present. Get your image now!