P5: The Universe Has No Boundary: Logical, Derivational, and Observational Arguments for Spatial Infinitude

This paper presents three independent categories of argument that the universe is spatially infinite and has nophysical boundary.The first is conceptual: a physical boundary of space is incoherent because any proposed boundary is eitherinside space — in which case it is a structure within space, not a limit of it — or it borders absolute non-being,which cannot function as a physical interface. The regress has no resolution within a finite model.The second is logical: the standard cosmological model's own answer to the singularity location question — thatthe singularity was everywhere simultaneously — is logically equivalent to asserting that the universe is spatiallyinfinite, directly contradicting the finite-origin premise. Standard responses (finite hypersphere, GR breakdown atthe Planck scale, inflation, loop quantum cosmology) each relocate rather than resolve this boundary condition.The third is derivational and observational: the cosmological constant Lambda, observed to have a positive value,provides a derivational proof of spatial infinitude through the Ricci tensor vanishing argument for an infiniteuniform distribution. Observationally, the isotropy of galaxy orientations, the persistence of large-scale orderedmotion at progressively larger scales, the absence of boundary pressure signatures, and the absence of anywraparound signal in CMB topology searches are all consistent with spatial infinitude and inconsistent with afinite bounded universe.An appendix demonstrates, via a reductio ad absurdum shell calculation, that any literal physical boundaryenclosing the observable universe would require a shell 5.9 million light years thick made of steel — 59 times thediameter of the Milky Way — with a mass 10^28 times that of the observable universe. The universe interior is avacuum (internal pressure effectively zero), so the shell must bear the full structural load with nocounter-pressure from within.Five falsifiable predictions are presented. This paper is part of the Big Flare-Up Theory (BFUT) framework (DOI:10.5281/zenodo.19149786).