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Science, Evolution, and Creationism, by the National Academies, focuses on teaching evolution in today's classrooms. Check out the other publications in our online store.

The Goldilocks Theory

Just as Goldilocks found the porridge that was just right, the Earth seems to be just right for conditions favorable to life. The reasons have to do with the fact that the Earth seems to be the perfect distance from the sun for abundant liquid water.

Venus is too close to the sun, and too hot for liquid water on its surface. In fact, it is so hot that the volatiles have all been driven into the atmosphere, so it has a thick and heavy atmosphere. Heat bakes the water out of the ground and prevents the special kind of hydrated minerals which allow for plate tectonics.

Mars is too far from the sun, and too cold for abundant liquid water on its surface. With no liquid water, the special kind of hydrated minerals which allow for plate tectonics are prevented from forming, and so atmospheric gases which become trapped within the ground stay trapped within the ground and are not recycled back to the atmosphere by way of volcanism. Thus over time Mars has developed a thin atmosphere, and all the water is frozen into the ground.

The temperature of Earth is just right for liquid water on the surface, and for the hydrated minerals which produce plate tectonics. With plate tectonics, atmospheric gases which become trapped within the ground are recycled back to the atmosphere in the form of volcanic emissions. These conditions favor repeated replenishment of the planet's atmosphere, which helps to maintain, via the greenhouse effect, surface temperatures just right for liquid water. These conditions are just right for abundant life

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Earth's Early Ocean

An ocean began to form on Earth as soon as the temperature fell from very hot, to about room temperature, a temperature where liquid water is stable. According to the Goldilocks theory, Earth is at just...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 rarely rise more than a thousand feet above their surroundings. They usually are created of eruptions from a single vent,...more

Flowing Lava

Lava can move in broad flat lava flows, or it can move through constrictive channels or tubes. Lava flows have a large surface area so they tend to cool quickly and flow slowly. The fastest unconstricted...more

How Do Plates Move?

Earth’s center, or core, is very hot, about 9000 degrees F. This heat causes molten rock deep within the mantle layer to move. Warm material rises, cools, and eventually sinks down. As the cool material...more

Clues to Plate Movements

Many kinds of surface features provide evidence of a sliding lithosphere. When two plates move apart, rising material from the mantle pushes the lithosphere aside. Two types of features can form when...more

Magma Chamber

Magma consists of remelted material from Earth's crust and fresh material from the aesthenosphere, relatively near the Earth's surface. When magma is erupted onto the surface in the form of lava, it becomes...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