# Photon Density of the Universe

The current temperature of the observable universe is about 2.7 K. What is the photon density of the universe in $$\frac{photons}{{m}^{3}}$$?

First calculate your answer in the form $$a\times { 10 }^{ b }$$, then input the value $\left\lceil a \right\rceil +b.$

Note: we assume that the universe is isotropic.

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