  We show that large gauge transformations in asymptotically flat spacetime can
be implemented by sandwiching a shell containing the ingoing hard particles
between two finite-width shells of soft gauge excitations. Integration of the
graviton Dirac bracket implies that our observable soft degrees of freedom obey
the algebra imposed by Strominger on unobservable boundary degrees of freedom.
Thus, we provide both a derivation and an observable realization of this
algebra. The conservation laws associated with asymptotic symmetries are seen
to arise physically from free propagation of infrared modes. This explains in
physical terms our recent result that soft charges fail to constrain the hard
scattering problem, and so cannot be relevant to the black hole information
paradox.
