  We present a study of the recently discovered spatially-extended chaotic
state known as spiral-defect chaos, which occurs in low-Prandtl-number,
large-aspect-ratio Rayleigh-Benard convection. We employ the modulus squared of
the space-time Fourier transform of time series of two-dimensional shadowgraph
images to construct the structure factor ${S}({\vec k},\omega )$.
  This analysis is used to characterize the average spatial and temporal scales
of the chaotic state. We find that the correlation length and time can be
described by power-law dependences on the reduced Rayleigh number ${\epsilon}$.
These power laws have as yet no theoretical explanation.
