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The Universe at Your Fingertips 2.0 DVD from the Astronomical Society of the Pacific is in our online store, filled with Earth and space science resources.

The Goldilocks Theory

Just as Goldilocks found the porridge that was just right, the Earth seems to be just right for living creatures. The Earth seems to be the perfect distance from the sun for lots of water.

Venus is too close to the sun, and too hot for flowing water on its surface. In fact, it is so hot that, like a sauna, all the water has been evaporated into the atmosphere, and Venus has a thick and heavy atmosphere.

Mars is too far from the sun, and too cold for flowing water on its surface. Mars also has no continental drift, so particles of the atmosphere which become trapped within the ground stay trapped within the ground. Thus over time the atmosphere of Mars has become thin, and all the water is frozen into the ground.

The temperature of Earth is just right for flowing water on the surface, and for the rock which allows for continental drift. With continental drift, particles of the atmosphere which become trapped within the ground are brought back to the atmosphere through eruptions of volcanoes. These conditions cause refreshment of the planet's atmosphere. A medium sized atmosphere helps keep temperatures just right for flowing water (through the greenhouse effect). These conditions are just right for abundant life

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Traveling Nitrogen Classroom Activity Kit

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Earth's Early Ocean

Once the Earth began to cool, water vapor, one of the volatiles, began to condense and form an ocean. According to the Goldilocks theory, Earth is at just the right distance from the sun for the temperature...more

The Climate of Mars

The unusual climate of Mars makes Mars not quite right for life as we know it on Earth. If the climate were warm enough, water would not freeze into the ground but vaporize into the atmosphere. Lots of...more

Volcanic Ash

Ash is made of millions of tiny fragments of rock and glass formed during a volcanic eruption. Volcanic ash particles are less than 2 mm in size and can be much smaller. Volcanic ash forms in several ways...more

Cinder Cones

Cinder cones are simple volcanoes which have a bowl-shaped crater at the summit and only grow to about a thousand feet, the size of a hill. They usually are created of eruptions from a single opening,...more

Flowing Lava

Lava can move in broad flat lava flows, or it can move through tight channels or tubes. Lava flows tend to cool quickly and flow slowly. The fastest lava outside of channels moves at about 6 mi/hr an easy...more

How Do Plates Move?

Plates at our planetís surface move because of the intense heat in the Earthís core that causes molten rock in the mantle layer to move. It moves in a pattern called a convection cell that forms when...more

Clues to Plate Movements

Many kinds of surface features are clues that our lithosphere is sliding. Two types of features can form when plates move apart. At mid ocean ridges, the bottom of the sea splits apart and new crust is...more

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