In order to better approximate and understand the exchange-correlation functional in density functional theory, the adiabatic connection curve is accurately calculated beyond the physical interaction strength using a simulated scaling method. This is done for Hooke's atom, two interacting electrons in a harmonic well potential. Extrapolation of the accurate curve to the infinite-coupling limit agrees well with the strictly correlated electron hypothesis. The interaction strength interpolation is shown to be a good, but not perfect, fit to the adiabatic curve. Arguments about the locality of functionals and convexity of the adiabatic connection curve are examined in this regime. (C) 2003 American Institute of Physics.