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Time-of-flight expansion of a Bose condensate. The first observations of BEC were made by suddenly turning off the trapping fields and allowing the atoms to expand ballistically. Absorption images were taken after a variable delay time. The earliest images show the pencil-like shape of the initial cloud. In the early phase of the expansion, the clouds appeared larger than their true sizes due to complete absorption of the probe laser light. Between 10 and 25 msec, the isotropic expansion of the normal component was observed. After 15 msec, the slower strongly anisotropic expansion of the Bose condensate became visible. When the cloud has expanded to many times its original size, such time-of-flight images represent the velocity distribution of the released cloud (in this figure, this applies only to the radial expansion). The width of the field of view is 1.6 mm.