S1.4.1

Knows that Earth systems have both internal and external sources of energy, both of which create heat; although the Sun is the major external source of energy, the decay of radioactive isotopes and gravitational energy from the Earth's original formation are primary sources of internal heat.

Making Clouds: Aerosol-Cloud Interactions in a Beaker

This example discusses the process of cloud formation and the ability of cloud droplets to scatter light. A demonstration \r\nthat creates a cloud in a beaker is described.

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Can an Astronaut on Mars distinguish the Earth from its Moon?

Some day an astronaut will stand on Mars and look back at Earth. As Alfred, Lord Tennyson wrote Venus, Hesper, Were we native to that splendour or in Mars We would see the globe we groan in, fairest of their evening stars Could we dream of wars and carnage, craft and madness lust and spite Roaring London, raving Paris, in that peaceful point of light? Would we not, when gazing heavenward, at a star so silver-fair Yearn, and clasp the hands, and murmur: Would to God that we were there? But what exactly will one see from Mars?

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