What arbitrary term did Einstein insert into his General Relativity equations, a modification later called his 'biggest blunder'?
Answer
The cosmological constant (\Lambda)
Einstein introduced the cosmological constant into his field equations specifically to force a static solution, counteracting the natural dynamic prediction of his own theory, because the prevailing scientific view favored an unchanging cosmos.

Related Questions
Where did the documented interactions between Albert Einstein and Edwin Hubble primarily take place?What arbitrary term did Einstein insert into his General Relativity equations, a modification later called his 'biggest blunder'?What was Edwin Hubble's crucial finding regarding 'spiral nebulae'?What relationship, now named after Hubble, describes the observation that farther galaxies recede faster?Which specific instrument was instrumental in Hubble's work that provided empirical evidence against a static universe?What fundamental difference in scientific methodology characterized Einstein compared to Hubble?What did Einstein reportedly remark about Hubble’s discovery of the expanding universe?What organizational body provided significant institutional backing and fostered the research environment at Mount Wilson?What is the conceptual model for the universe's origin that flows naturally from extrapolating Hubble's observations backward in time?When did Einstein, accompanied by his wife Elsa, reportedly visit Mount Wilson Observatory?