Pressure is a measure of force distributed over a specific area, governing the state of matter across the universe. The range of pressures encountered in science is immense, spanning from the near-vacuum of interstellar space to the forces within stellar cores. Scientists work to recreate extreme conditions in highly controlled laboratory environments to understand how matter behaves under compression.
Defining the Absolute Pressure Record
The highest pressure ever recorded and sustained in a laboratory setting has been achieved using specialized equipment. The most reliable method for generating stable, ultra-high pressure is the Diamond Anvil Cell (DAC), which presses a tiny sample between the tips of two perfect, gem-quality diamonds. These diamonds are the strongest material known, allowing them to withstand immense force concentrated onto a microscopic area.
A specific, reliably measured static pressure of 640 Gigapascals (GPa) has been generated using a DAC, though pressures up to 770 GPa have been reported as possible under ideal conditions. To put this force into perspective, 1 GPa is approximately 10,000 times the atmospheric pressure at sea level. The DAC achieves this staggering compression by applying a relatively small mechanical force to the back of the diamonds, which is then amplified due to the extremely small size of the diamond tips, or culets.
Transient, non-sustained pressures that are even higher can be generated using dynamic compression techniques like shock waves created by high-velocity projectiles or lasers. These shock experiments can momentarily achieve pressures reaching tens of millions of atmospheres, or terapascal levels, but only for fractions of a second. This technique generates heat, which makes it challenging to disentangle the effects of extreme pressure from the effect of high temperature on the sample. The DAC, in contrast, provides a static, stable environment for prolonged study, which is why it holds the record for the highest measured, sustained pressure.
Pressures Found in Nature
The immense pressures created in the laboratory are often used to mimic and study the conditions found in deep geological and astrophysical environments. Even the deepest point on Earth, the Challenger Deep in the Mariana Trench, has a pressure of about 111 Megapascals (MPa), roughly 1,100 times the pressure at the surface. This is a crushing force for surface life, but it is less than one-thousandth of the pressure created by a DAC.
Moving inward, the Earth’s inner core experiences far greater compression due to the weight of all the overlying rock and metal. The pressure at the very center of the Earth is estimated to be between 330 and 360 GPa. This pressure is why the iron-nickel alloy at the core remains solid despite being close to the temperature of the sun’s surface.
However, the highest pressures in the universe far exceed anything achievable on Earth. These pressures are inferred, not directly measured, and exist in massive celestial objects. For example, the core of a neutron star is predicted to reach pressures on the order of \(10^{14}\) GPa, crushing matter into an exotic, ultra-dense state. Comparing these natural extremes to the lab’s 770 GPa highlights the vast scale of pressure in the cosmos.
Applications of Extreme Pressure Research
The pursuit of record-breaking pressure is driven by the desire to understand and manipulate matter at its most fundamental level. Extreme pressure forces atoms closer together, fundamentally altering the way they interact and bond. This compression can cause a substance to undergo a phase transition, leading to the discovery of entirely new materials that cannot be created under normal atmospheric conditions.
One of the primary goals is the synthesis of novel, technologically relevant materials, such as new forms of superconductors. By squeezing materials, scientists have created unique structures, including certain hydrides that exhibit superconductivity at higher temperatures than their normal-pressure counterparts. Extreme pressure research is also used to create super-hard materials, like new forms of carbon that exceed the hardness of natural diamond.
In planetary science, these experiments allow geophysicists to recreate the conditions of planetary interiors to understand the composition and dynamics of Earth’s core and the deep interiors of ice giants. Studying common elements like hydrogen under extreme pressure has led to the prediction and observation of metallic hydrogen, a state theorized to exist deep within gas giants like Jupiter. Using pressure as a clean, tunable variable, researchers gain insight into how atomic structure dictates physical properties, paving the way for the development of materials with unprecedented functionality.