Editing Geometrized unit system (section)

==Definition==
Geometrized units were defined in the book [[Gravitation (book)|''Gravitation'']] by [[Charles W. Misner]], [[Kip S. Thorne]], and [[John Archibald Wheeler]] with the [[speed of light]], <math>c</math>, the [[gravitational constant]], <math>G</math>, and [[Boltzmann constant]], <math>k_b</math> all set to 1.<ref name=MisnerThorneWheeler/>{{rp|36}} Some authors refer to these units as geometrodynamic units.<ref>{{Cite journal|arxiv=2009.12057|doi=10.1103/PhysRevD.103.084052|title=Novel black-bounce spacetimes: Wormholes, regularity, energy conditions, and causal structure|year=2021|last1=Lobo|first1=Francisco S. N.|last2=Rodrigues|first2=Manuel E.|last3=Silva|first3=Marcos V. de S.|last4=Simpson|first4=Alex|last5=Visser|first5=Matt|journal=Physical Review D|volume=103|issue=8|page=084052|bibcode=2021PhRvD.103h4052L|s2cid=235581301}}</ref>

In geometric units, every time interval is interpreted as the distance travelled by light during that given time interval. That is, one [[second]] is interpreted as one [[light-second]], so time has the geometric units of [[length]]. This is dimensionally consistent with the notion that, according to the [[kinematics|kinematical]] laws of [[special relativity]], time and distance are on an equal footing.

[[Energy]] and [[momentum]] are interpreted as components of the [[four-momentum]] vector, and [[mass]] is the magnitude of this vector, so in geometric units these must all have the dimension of length. We can convert a mass expressed in kilograms to the equivalent mass expressed in metres by multiplying by the conversion factor ''G''/''c''<sup>2</sup>. For example, the [[Sun]]'s mass of {{val|2.0|e=30|u=kg}} in SI units is equivalent to {{val|1.5|u=km}}. This is half the [[Schwarzschild radius]] of a one solar mass [[black hole]]. All other conversion factors can be worked out by combining these two.

The small numerical size of the few conversion factors reflects the fact that relativistic effects are only noticeable when large masses or high speeds are considered.