theory: background radiation is actually alien messages. The sky is completely filled with it.
The reason we can't read it as a signal is not because it has diffused, but because it's compressed so effectively that, for us, it is indistinguishable from noise.
The reason we can't read it as a signal is not because it has diffused, but because it's compressed so effectively that, for us, it is indistinguishable from noise.