Astrophysics (Index)About


(order-of-magnitude, decimal exponent)
(a number or factor's log base 10)

Dex (for decimal exponent) refers to the exponent of a number in scientific notation, and is also used like a unit that specifies a number's order-of-magnitude. For example, 100 could be described as 2 dex, or two numbers that differ by a factor of 1000 could be said to differ by 3 dex. As a unit, a number of dex is sometimes cited as a fraction (amounting to the log base 10) whereas an order-of-magnitude is commonly rounded to an integer. Within physics and astrophysics, the term dex is sometimes used, but order-of-magnitude is probably used more. A common circumstance is describing the ratio of two numbers by the ratio's dex or order-of-magnitude. Example number:


The number's dex as specified is 7 and the number could be described as "7 dex" or "having an order-of-magnitude of 7". It could also be described as "7.38 dex", which is the number's log base 10 not rounded to an integer.

Further reading:

Referenced by pages:
axion (A0)
CMB Stage-4 (CMB-S4)
cosmic dust
dark energy
dense core mass function (DCMF)
event horizon (EH)
exascale computing
free-fall time
fuzzy dark matter (FDM)
H-R diagram (HRD)
hyperfine structure
ionizing radiation
jansky (Jy)
Kelvin-Helmholtz timescale (KH timescale)
N-body problem
numerical analysis
planet formation
parts per million (PPM)
projected separation
superluminous supernova (SLSN)
speed of light (c)
stellar dynamics
task-based parallelism (TBP)
time standard
valley of beta stability