This paper presents large-scale polarization maps (8@ ] 8@) of the Orion molecular cloud (OMC-1) at far-infrared (100 km ; 35A resolution) and submillimeter (350 km ; 18A resolution) wavelengths. The magnetic Ðeld shows a pinch at scales less than 0.5 pc with a centroid that is on the OMC-1 ridge, a site of high-mass star formation. We infer that gravitational collapse pulled the magnetic Ðeld into an hourglass shape. We estimate that the magnetic, kinetic, and gravitational energies are in equipartition on the ridge and that the magnetic energy dominates in the surrounding ambient envelope. We consider a model in which the ridge and thus high-mass stars gravitationally collapsed out of a cloud that was initially supported by the magnetic Ðeld. At Ñux peaks, there is a reduction in the percent polarization. This e †ect is discussed in relation to temperature, optical depth, and wavelength.

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