Matter & Energy


Matter is composed of atoms or groups of atoms called molecules. The arrangement of particles in a material depends on the physical state of the substance. In a solid, particles form a compact structure that resists flow. Particles in a liquid have more energy than those in a solid. They can flow past one another, but they remain close. Particles in a gas have the most energy. They move rapidly and are separated from one another by relatively large distances.

Solar Energy from Space

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A futuristic proposal to produce power on a large scale envisions placing giant solar modules in geostationary Earth orbit. Energy generated from sunlight would then be converted to microwaves and beamed to antennas on Earth for conversion to electric power. The Sun would shine on a solar collector in geostationary orbit almost 24 hours a day; moreover, such a collector would be high above the atmosphere and so would receive the full power of the Sun’s rays. Consequently, such a collector would gather eight times more light than a similar collector on the ground. To produce as much power as five large nuclear power plants (1 billion watts each), several square miles of solar collectors, weighing 10 million pounds, would need to be assembled in orbit. An Earth-based antenna five miles in diameter would be required to receive the microwaves. Smaller systems could be built for remote islands, but the economies of scale suggest advantages to a single large system (see Space Exploration).