Mass
![The kilogram is one of the seven SI base units and one of three which is defined ad hoc (i.e. without reference to another base unit).](/Images/godic/202502/01/SI_base_unit.svg5121.png")
![The relation between properties of mass and their associated physical constants. Every massive object is believed to exhibit all five properties. However, due to extremely large or extremely small constants, it is generally impossible to verify more than two or three properties for any object.
The Schwarzschild radius (rs) represents the ability of mass to cause curvature in space and time.
The standard gravitational parameter (μ) represents the ability of a massive body to exert Newtonian gravitational forces on other bodies.
Inertial mass (m) represents the Newtonian response of mass to forces.
Rest energy (E0) represents the ability of mass to be converted into other forms of energy.
The Compton wavelength (λ) represents the quantum response of mass to local geometry.](/Images/godic/202502/01/MassProperties.svg5121.png")
![Depiction of early balance scales in the Papyrus of Hunefer (dated to the 19th dynasty, ca. 1285 BC). The scene shows Anubis weighing the heart of Hunefer.](/Images/godic/202502/01/Weighing_of_the_heart35121.jpg")
![Galileo Galilei (1636)](/Images/godic/202502/01/Galileo.arp.300pix5121.jpg")
In physics, mass is a property of a physical body. It is generally a measure of an object's resistance to changing its state of motion when a force is applied. It is determined by the strength of its mutual gravitational attraction to other bodies, its resistance to acceleration or directional changes, and in the theory of relativity gives the mass–energy content of a system. The SI unit of mass is the kilogram (kg).