## The size of what can be known

### December 15, 2013

The Planck length is estimated at $1.616199(97) \times 10^{-35}$ meters, whereas the radius of the observable Universe (comoving distance to the Cosmic Microwave Background) is $46.6 \times 10^{9}$ light years, i.e. $4.41 \times 10^{26}$ meters.

Both represent the metric limits of what we can perceive, regardless of the observation technique: the Planck length corresponds to the smallest measurable distance, whereas the observable radius of the Universe corresponds to the most ancient observable radiation (the CMB is the redshifted light emitted at the end of the Inflationary Epoch).

The existence of universes whose Planck length is larger than the observable size of ours (or, whose universe is bounded by our Planck length) is not provable. A fractal nesting of turtles.

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