Explorable

Bend space: triangles and the size of the universe

Choose how curved space is and see how a 45-billion-light-year triangle’s angles change, how big a closed universe would be, and whether today’s data allow it.

Curvature parameter−0.0020

ΩK in the text. Negative = closed (ball-like), positive = open (saddle-like).

Triangle side45 billion ly

Compare with

PlanckACTDESI

ANGLE SUM180.478 °

CURVATURE RADIUS325 billion ly

TOTAL VOLUME1,640 × what we see

IF CLOSED, ALLOWED BY PLANCK?yes (95%)

A closed universe with this curvature is a three-sphere about 2,039 billion light-years around, measured at one instant. Because the expansion is speeding up, not even light could ever complete the trip (if dark energy stays constant).

The physics, the assumptions behind this tool and the sources are explained in Is the universe infinite?.

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