Hyperbolic motion (relativity)

Encyclopedia

**Hyperbolic motion**is the motion of an object with constant proper acceleration

Proper acceleration

In relativity theory, proper acceleration is the physical acceleration experienced by an object. It is acceleration relative to a free-fall, or inertial, observer who is momentarily at rest relative to the object being measured...

in special relativity

Special relativity

Special relativity is the physical theory of measurement in an inertial frame of reference proposed in 1905 by Albert Einstein in the paper "On the Electrodynamics of Moving Bodies".It generalizes Galileo's...

. It is called hyperbolic motion because the equation describing the path of the object through spacetime

Spacetime

In physics, spacetime is any mathematical model that combines space and time into a single continuum. Spacetime is usually interpreted with space as being three-dimensional and time playing the role of a fourth dimension that is of a different sort from the spatial dimensions...

is a hyperbola

Hyperbola

In mathematics a hyperbola is a curve, specifically a smooth curve that lies in a plane, which can be defined either by its geometric properties or by the kinds of equations for which it is the solution set. A hyperbola has two pieces, called connected components or branches, which are mirror...

, as can be seen when graphed on a Minkowski diagram

Minkowski diagram

The Minkowski diagram was developed in 1908 by Hermann Minkowski and provides an illustration of the properties of space and time in the special theory of relativity. It allows a quantitative understanding of the corresponding phenomena like time dilation and length contraction without mathematical...

.

The proper acceleration of a particle is defined as the acceleration

Acceleration

In physics, acceleration is the rate of change of velocity with time. In one dimension, acceleration is the rate at which something speeds up or slows down. However, since velocity is a vector, acceleration describes the rate of change of both the magnitude and the direction of velocity. ...

that a particle "feels" as it accelerates from one inertial reference frame to another. This can be derived mathematically as

,

where is the instantaneous speed of the particle. Solving for the equation of motion results in

,

which is a hyperbola.

Hyperbolic motion is easily visualized on a Minkowski diagram, where the motion of the accelerating particle is along the -axis. Each hyperbola is defined by

.