Magnituderna

Magnitudes (magnituderna in Swedish) are terms used across several disciplines to describe the size or strength of a quantity. The concept appears in mathematics, physics, astronomy and geophysics, and serves to compare sizes or strengths across phenomena.

In mathematics, magnitude means size or length; for a vector v, |v| is its Euclidean norm; for a complex number z, |z| is its modulus; for a real number x, |x| is its absolute value. Magnitude also relates to distance and measurement in geometry and analysis.

The concept of order of magnitude refers to rough scales, typically expressed as powers of ten, used for estimation and comparison when exact values are unnecessary.

In astronomy, magnitude is a logarithmic brightness scale. Apparent magnitude m measures how bright an object looks from Earth; absolute magnitude M denotes intrinsic brightness at 10 parsecs. Brighter objects have smaller magnitudes. Flux relates by F ∝ 10^(-0.4 m); the distance modulus m - M = 5 log10(d/10 pc) connects distance and brightness. Magnitudes are defined for specific filters (e.g., V) with standard zero points.

In geophysics, earthquake magnitudes quantify energy release. Local magnitude ML and mb describe parts of the spectrum; moment magnitude Mw provides a scale valid for all sizes. Magnitude correlates with energy but depends on distance, attenuation, and how it is measured.

Historically, the term derives from Latin magnitudo; Pogson formalized the astronomical scale in the 19th century. Today magnitudes remain a foundational concept for comparing sizes and brightness across diverse phenomena.