The terapascal is a unit of pressure equal to a thousand gigapascals, written TPa. It is ten million bar. Nothing built by engineers operates at this pressure, and the unit belongs instead to two quite separate corners of science: the stiffness of the strongest materials known, and the interiors of large planets.
Carbon nanostructures put it on the map. A single-walled carbon nanotube has a Young's modulus close to one terapascal, and a sheet of graphene the same, which makes them the stiffest materials ever measured relative to their weight. Diamond, long the benchmark, comes in at 1.2 terapascals. Those three numbers are the reason the unit appears at all in materials science.
Stiffness at this level is not the same as strength. A nanotube resists stretching enormously, but a real fibre made of many of them fails at a far lower stress because the tubes slide past one another. Confusing a terapascal modulus with a terapascal breaking strength is one of the commonest errors in popular accounts of these materials.
Planetary interiors reach genuine terapascal pressures. The centre of Jupiter is estimated at three to four terapascals, and the cores of larger gas giants beyond that. Under such conditions hydrogen behaves as a metal, which is what generates the planet's magnetic field, so the unit describes a state of matter rather than a load on a structure.
Laboratories can now reach it briefly. Laser-driven shock compression and pulsed magnetic techniques drive samples into the terapascal range for nanoseconds at a time, long enough to record how a material's density and structure respond. Those experiments are the only direct evidence available about matter under the conditions inside giant planets.
For scale, one terapascal is ten million times atmospheric pressure and about a thousand times the pressure at the centre of the earth divided by three. The number stops being something a person can feel and becomes a description of what atoms do when they are pushed close enough together to change their chemistry.
One terapascal equals 1,000,000,000,000 pascals, 1000 gigapascals, 10,000,000 bar, or about 145 million pounds per square inch.
| Unit | Symbol | 1 Terapascal equals | 1 of these equals | Converter |
|---|---|---|---|---|
| Nanopascal | nPa | 1 × 1021 nPa | 1 × 10-21 TPa | Terapascals to Nanopascals |
| Micropascal | µPa | 1 × 1018 µPa | 1 × 10-18 TPa | Terapascals to Micropascals |
| Millipascal | mPa | 1 × 1015 mPa | 1 × 10-15 TPa | Terapascals to Millipascals |
| Centipascal | cPa | 100000000000000 cPa | 1 × 10-14 TPa | Terapascals to Centipascals |
| Decipascal | dPa | 10000000000000 dPa | 1 × 10-13 TPa | Terapascals to Decipascals |
| Pascal | Pa | 1000000000000 Pa | 1 × 10-12 TPa | Terapascals to Pascals |
| Newton per square meter | N/m² | 1000000000000 N/m² | 1 × 10-12 TPa | Terapascals to Newtons per square meter |
| Decapascal | daPa | 100000000000 daPa | 1 × 10-11 TPa | Terapascals to Decapascals |
| Hectopascal | hPa | 10000000000 hPa | 1 × 10-10 TPa | Terapascals to Hectopascals |
| Kilopascal | kPa | 1000000000 kPa | 0.000000001 TPa | Terapascals to Kilopascals |
| Bar | bar | 10000000 bar | 0.0000001 TPa | Terapascals to Bars |
| Megapascal | MPa | 1000000 MPa | 0.000001 TPa | Terapascals to Megapascals |
| Gigapascal | GPa | 1000 GPa | 0.001 TPa | Terapascals to Gigapascals |
| Atmosphere | atm | 9869232.66716 atm | 0.000000101325 TPa | Terapascals to Atmospheres |
| Pound per square inch | psi | 145037737.73 psi | 0.00000000689475729317 TPa | Terapascals to Pounds per square inch |
| Kilopound per square inch | ksi | 145037.743897 ksi | 0.000006894757 TPa | Terapascals to Kilopounds per square inch |
| Megapound per square inch | Mpsi | 145.037743897 Mpsi | 0.006894757 TPa | Terapascals to Megapounds per square inch |