La Tierra

1. Other molecules enveloping a planet, such as oxygen, ozone and methane, can suggest that life itself has taken root. On Earth, oxygen is "breathed out" by plants, and methane by micro-creaturesliving in swamps and animals. These chemicals don't stick around for long on their own, so if they are hanging around an extrasolar planet, then something must be pumping the stuff out. That somethingcould be life, but this isn't always the case. Saturn's moon's Titan is shrouded in an atmosphere containing lots of methane not produced by life.


2. The energy source that creates the auroraoriginates from the solar wind, an electrically charged gas (plasma) released by the sun that impacts the Earth's magnetic field. This energy ultimately sets up electric fields in space that accelerateelectrically charged particles trapped in the Earth's magnetic field. The particles slam into the upper atmosphere above the polar regions, generating the dynamic and beautiful glow we know as theaurora.


3. Scientists say that oxygen is a more reliable sign of life than methane, but if they found large quantities of both, they'd be more convinced. "Finding two of these molecules together wouldbe much better than one. The more, the better," said Dr. Victoria Meadows of NASA's Spitzer Science Center, Pasadena, who served as chair of the third Pale Blue Dot conference. "For example, if wefound carbon dioxide, oxygen and water vapor, in addition to methane, then we'd be pretty convinced that we were looking at an environment like our own."


Taken from:http://education.nasa.gov/home/index.html


4. This account of the making of the Great Pyramid, although rich and coherent, does not satisfy everyone, and there are many who persist in attributing the Great Pyramid to someagency outside the human race. There is a whole branch of the publishing industry devoted to meeting this hunger for pyramidical mysteries, which is sharpened by movies such as Stargate and The Fifth...