Trade involves the transfer of goods or services from one person or entity to another, often in exchange for money. A system or network that allows trade is called a market.
The product of mental labor — science — always stands far below its value, because the labor-time necessary to reproduce it has no relation at all to the labor-time required for its original production.
Karl Marx Addenda, "Relative and Absolute Surplus Value" in Economic Manuscripts (1861–63).
Although the Earth is a rocky planet, many aqueous dynamic processes take place beneath its surface making it unique among terrestrial planets. New insight into the role of fluids on properties of materials is directly relevant to earthquakes and volcanic eruptions.
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