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См. также в других словарях:

• Free space — In classical physics, free space is a concept of electromagnetic theory, corresponding to a theoretically perfect vacuum, and sometimes referred to as the vacuum of free space. The definitions of the ampere and meter SI units are based upon… …   Wikipedia

• Trophic level — First trophic level The plants in this image, and the algae and phytoplankton in the lake, are primary producers. They take nutrients from the soil or the water, and manufacture their own food by photosynthesis, using energy from the sun. The… …   Wikipedia