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Become a nitrogen atom in the nitrogen cycle in our Traveling Nitrogen Classroom Activity Kit/Game. See all our games, activity kits and classroom activities.


Earth, our home planet, is a beautiful blue and white ball when seen from space. The third planet from the Sun, it is the largest of the inner planets. Earth is the only planet known to support life and to have liquid water at the surface. Earth has a substantial atmosphere and magnetic field, both of which are critical for sustaining life on Earth. Earth is the innermost planet in the solar system with a natural satellite – our Moon. Explore our beautiful home planet – unique in our solar system - through the links in this section.

As temperatures rise and soil moisture decreases, plants are stressed, which can lead to <a href="/earth/climate/crops_withering.html&dev=1">crop withering</a>. <a href="/teacher_resources/online_courses/health/events_health.html&dev=1">Droughts</a> accompanied by increased temperatures can lead to famine, social and political disruptions. Scientists are  helping with early identification of drought that might trigger food shortages. Watch the NBC Learn video - <a href="/earth/changing_planet/withering_crops_intro.html&dev=1">Changing Planet: Withering Crops</a> to find out more.<p><small><em>Image taken by Tomas Castelazo, Creative Commons <a href=&quot;;>Attribution 3.0 Unported</a> license.</em></small></p>How did life evolve on <a href="/earth/earth.html&dev=1">Earth</a> during the <a href="/earth/past/Archean.html&dev=1">Archean</a>, when the <a href="/sun/sun.html&dev=1">Sun</a> was about 25% weaker than today?  The Earth should have been <a href="/earth/polar/cryosphere_glacier1.html&dev=1">glaciated</a>, if <a href="/earth/climate/earth_greenhouse.html&dev=1">greenhouse</a> gas concentration was the same as today.  <a href="">Researchers</a> studying the <a href="/physical_science/physics/atom_particle/isotope.html&dev=1">isotopic</a> signatures of Earth's early atmosphere in <a href="/earth/geology/rocks_intro.html&dev=1">rocks</a> from Northern Australia have ruled out high levels of <a href="/physical_science/chemistry/nitrogen_molecular.html&dev=1">nitrogen</a> as a possible way to increase warming from <a href="/earth/Atmosphere/overview.html&dev=1">atmospheric</a> <a href="/physical_science/chemistry/carbon_dioxide.html&dev=1">carbon dioxide</a>.<p><small><em>Image courtesy of Manchester University</em></small></p>This iconic image of Earth rising above the surface of the <a
  was taken on December 24, 1968 by astronauts on the <a
  href="/space_missions/apollo8.html&dev=1">Apollo 8
  mission</a>.  Apollo 8 was the first <a
  mission</a> to the Moon, and entered into lunar orbit on Christmas Eve.  That
  evening, the astronauts held a live broadcast from lunar orbit, in which they showed pictures of the Earth and moon as seen from their
  spacecraft.<p><small><em> Image courtesy of   NASA</em></small></p>Coral animals build reefs in warm, tropical seawater. However, <a href="/earth/changing_planet/ocean_temperatures_intro.html&dev=1">seawater can be too warm</a> for their liking.  If waters get too warm, coral animals lose the algae that live within their little bodies, a process called coral bleaching. Without the algae, corals have less nutrition. Unless cooler temperatures return, allowing algae to
 return, the coral dies.<p><small><em>Credit: UNC</em></small></p>An artist's rendering of the moment of impact of a massive <a
  at the end of the Cretaceous (at the end of the <a
  Era</a>). Many
  scientists have concluded for decades that a meteorite four to six kilometers
  in diameter impacted the Earth at this time, resulting in a <a
  href="/earth/past/KTextinction.html&dev=1">mass extinction
  of dinosaurs</a> and many other life forms.  Recent research suggests that
 perhaps <a
  volcanic eruptions</a> may be been responsible for the extinction.<p><small><em>Courtesy of Don Davis, NASA</em></small></p>A sinuous glowing band of <a
  href="/earth/Magnetosphere/aurora.html&dev=1">aurora</a> (the Aurora Australis
  or Southern Lights) loops around the <a
  href="/earth/polar/polar_south.html&dev=1">southern polar</a>
region in the
  distance as viewed by astronauts onboard the space shuttle on <a
  href="/earth/Magnetosphere/aurora/aurora_colors.html&dev=1">Aurora are produced</a>
  when <a
  href="/physical_science/physics/atom_particle/particle_radiation.html&dev=1">energetic particles</a>
 entering the Earth's
  atmosphere from space interact with <a
  href="/physical_science/physics/atom_particle/atom.html&dev=1">atoms</a> and <a
  href="/earth/geology/molecule.html&dev=1">molecules</a> in the atmosphere and
  release energy, emitted as light. <p><small><em>Courtesy of NASA, Astronaut Overmeyer and Dr. Hallinan</em></small></p>

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA