Building codes prevent overloading a house's foundation — otherwise it cracks. Einstein's field equations also have their own 'building codes': they set a limit on the force of gravity that no star or planet can exceed. At the core is the famous number c⁴/G, the Planck force, about 10⁴⁴ newtons.

In 2002, physicists suggested that this is the maximum possible force in nature. However, it was long impossible to prove this for real objects without black holes. Recently, Shahar Hod derived strict bounds directly from the field equations. He considered spherical bodies (stars, white dwarfs, neutron stars) and introduced a force function — the product of pressure and surface area of a sphere. It turned out that depending on the properties of matter, this function cannot exceed 2, 1, or even 0.5. The strictest limit — 0.5 — applies to most known substances where the sum of energy and pressure is non-positive. In other words, the real maximum force is about half of c⁴/G.

These numbers are exact consequences of the theory. They serve as cosmic building codes: if future observations of supernovae or gravitational waves show a deviation, it would indicate new physics. Just as an engineer checks a foundation against codes, astrophysicists can now test the most extreme objects in the universe.