A unit of pressure equal to one billion pascals, commonly used in high-pressure physics.A gigapascal (GPa) is a unit of pressure equal to one billion pascals, where one pascal is one newton per square meter. This is an enormous pressure, roughly 10,000 times the atmospheric pressure at sea level. Gigapascal pressures are typical of the conditions deep inside the Earth, in the cores of planets, and in laboratory experiments using diamond anvil cells to study materials under extreme compression.
The pascal was named after Blaise Pascal, the 17th-century French mathematician and physicist who studied fluid pressure. The gigapascal prefix was adopted with the SI system in the 20th century, and its use became widespread with the development of high-pressure experimental techniques in the 1950s and 1960s.
Pressure is force per unit area, and a gigapascal corresponds to the weight of about 10,000 kilograms pressing on every square centimeter. At such pressures, the distances between atoms shrink significantly, altering electronic structure, chemical bonding, and even causing phase transitions—for example, carbon transforms into diamond at about 5 GPa. The gigapascal is a convenient unit because it avoids unwieldy numbers when describing these extreme conditions.
Gigapascal pressures are used in materials science to synthesize superhard materials like synthetic diamonds and cubic boron nitride, and in geophysics to simulate the conditions of planetary interiors.
The pressure at the center of the Earth is about 360 GPa, which is roughly the same as the pressure exerted by the weight of a small car resting on the tip of a ballpoint pen.
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