Umlaufzeiten

Umlaufzeiten is a German term used to describe the duration of a complete cycle or orbit in different scientific contexts. In astronomy and orbital mechanics, the Umlaufzeit of an astronomical body is the period required to complete one orbit around a central mass. For a body in a Keplerian orbit around a mass M with gravitational parameter μ = G M, the orbital period T is given by T = 2π sqrt(a^3/μ), where a is the semi-major axis. In the case of circular or near-circular orbits, a is the orbital radius. Orbital periods are commonly expressed in days or years and are linked to the size of the orbit by Kepler’s laws.

In medicine and physiology, Umlaufzeit can refer to the circulation time—the time needed for blood to complete a full circuit through the cardiovascular system. This is often assessed with imaging techniques that track a contrast agent, measuring transit times between specific cardiovascular landmarks. Circulation time depends on factors such as cardiac output, vascular resistance, and body size, and can provide information about cardiovascular status, hemodynamic efficiency, and the effects of interventions or disease states.

The term Umlaufzeit derives from umlaufen, to go around, and Zeit, time. It thus captures the general notion of a cycle duration in systems that exhibit repetitive motion or flow. See also orbital period and circulation time.