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).
The brightness of the Sun varies on all time scales and wavelengths. An EU-funded initiative is gathering scattered observations from over 25 instruments to accurately represent how solar irradiance variability influences Earth's climate.
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