The pascal (Pa) is the base unit of pressure in the International System of Units (SI), defined as the force of one newton distributed over one square meter. For measuring extreme environments, a larger unit is needed. The prefix “Giga” represents one billion, meaning a Gigapascal (GPa) is equivalent to \(10^9\) pascals.
Scaling the Gigapascal: How Much Pressure Is That?
1 GPa represents an immense concentration of force. To put this into perspective, 1 GPa is roughly equivalent to 10,000 times the standard atmospheric pressure at sea level. It also translates to approximately 145,038 pounds per square inch (PSI). This scale is necessary when discussing the strength of materials or environments where matter is significantly compressed.
For visualization, a pressure of just 0.6 GPa is comparable to balancing the total weight of three jumbo jets on a surface the size of a smartphone. Remarkably, the microscopic water bear, or tardigrade, has been shown to survive momentary shock pressures exceeding 1.14 GPa.
Applying Extreme Pressure in Industry
GPa levels of pressure are utilized in engineering to create novel materials and preserve food. The most demanding industrial process is the high-pressure, high-temperature (HPHT) synthesis of materials like artificial diamonds. Converting graphite into diamond requires pressures ranging from 5 GPa up to 25 GPa, sustained within massive, specialized presses.
A more widespread industrial use is High-Pressure Processing (HPP) in the food industry. HPP subjects packaged foods to pressures between 0.4 and 0.6 GPa, using water to transmit the force uniformly. This process inactivates spoilage microorganisms and pathogens without using heat, extending shelf life while maintaining the food’s fresh flavor and nutritional content.
Gigapascals in Earth and Space Science
The Gigapascal scale describes the extreme conditions found within planets and stars. Within Earth, pressure increases steadily from the surface. The planet’s lower mantle reaches pressures of around 60 GPa. At the boundary between the inner and outer core, the pressure is estimated to be over 330 GPa, which is required to compress iron and nickel into a solid state despite the extreme heat.
Astrophysicists rely on GPa to characterize environments on gas giants. Within the massive atmospheres of planets like Jupiter, pressure increases to hundreds of GPa. These pressures force hydrogen gas into liquid metallic hydrogen, altering its electrical properties and creating the planet’s powerful magnetic field.