Eric B. Ford, an assistant professor of astronomy at the University of Florida, is one of five authors of a paper within the online version of the Astrophysical Journal.

Ford states that an alien-sized telescope, such as the Hubble Space Telescope, could observe the Sun and examine Earth from another planet. He states, “They would only be able to see Earth as a single pixel, rather than resolving it to take a picture. But that could be enough for them to identify our planet as one that likely contains clouds and oceans of liquid water.” [Science Daily: “To Curious Aliens, Earth Would Stand Out As Living Planet”]

Another author of the study, Enric Palle, an astronomer with the Instituto de Astrofisica de Canarias (an astrophysical research institute at Tenerife in the Canary Islands, Spain), states that their research is intended not to show whether aliens can find the Earth, but whether Earthlings can someday find Earth-like planets out there close to our solar system and beyond.

Astonomers have already discovered hundreds of Jupiter-sized planets orbiting stars other than the Sun (what are called exosolar planets, or exoplanets). With a bit more powerful telescopes, we will able in a few decades to study, in earnest, Earth-like planets that might be habitable by intelligent life.

Astronomers want to eventually be able to discover exoplanets that might harbor life. To contain life, scientists think that such planets should have a protective atmosphere (to protect its life forms), and to be just the right distance from its star (not too far away, too cold, and not too close, too hot, but just at the right distance, perfect for life to develop).

Thus, Ford, Palle, and their associates are studying how Earth would appear to inquisitive aliens in order to decide how future space telescopes should be built by humans and where they should be directed in the universe in order to detect planets similar to Earth in composition and in distance from our Sun. (Kinda like reverse psychology but applied to astronomy.)

They have already discovered that an alien telescope would have to observe Earth for long periods of time in order to collect sufficient light to identify chemicals in our atmosphere.

When sufficient light is collected, they would find that the brightness of the Earth changes due to its varying cloud cover. Thus, if these aliens could measure our planet’s rotational period based on these cloud formations, they would be able to find out important information about our home planet.

The Ford-Palle team has discovered that even though our atmosphere appears to be an apparently mixed-up  state of atmospheric patterns, it really is not. In fact, they have found that Earth consistently shows cloudy areas over rain forests, while little cloud cover appears over dry and arid regions. Something we could expect and something that alien observers could surmise after looking at Earth for awhile.

These repeating patterns of cloudy areas, then cloudless areas, would eventually make the aliens conclude that we had a 24-hour rotation period. The aliens would then start to deduce more specific information about our planet such as weather patterns, major storms, continents and oceans, and other such atmospheric and geological phenomenon.