Currently, only one spacecraft inhabits L2: the US space agency's WMAP probe (which is making observations on which Planck hopes to build).

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The energy that would be needed to probe the granularity of space is known as the Planck energy.

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Details of these predicted variations have been confirmed by the Wilkinson Microwave Anisotropy Probe (WMAP) and other experiments, and will be further tested by the Planck satellite, data from which is currently under analysis.

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