Near–field radiative transfer between two objects can be enhanced by a few order of magnitude compared to the far–field radiative transfer that can be described by Planck’s theory of blackbody radiation and Kirchoffs laws. We have developed a numerical technique to determine the near–field thermal radiative transfer between two spheres. We have measured near–field thermal radiation between a silica sphere and a flat silica substrate as a function of gap between them using an bi–material cantilever as a thermal sensor. The experimental results show qualitative agreement with numerical results. The results of this work indicate that the proximity force approximation, widely used to determine forces between curved objects, is not applicable to near–field radiative transfer between curved objects.

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