From what I can understand, Cosmic Microwave Background Radiation (CMBR) is microwave now, but was initially visible light emitted long time ago.
The microwave is producing a wave that’s about 12 centimeters long.
Now CMBR has right now this (time changing) distribution (peak at 2mm):
By Quantum Doughnut - Own work
This diagram was created with gnuplot., Public Domain, Link
So it looks to me that in some time, when its wavelength falls at around 12cm), some of its energy should be transferred to water molecules the way it is in a microwave oven.
- Is it the case? Will some of the CMBR energy actually transferred to water molecules?
- Will this energy be too faint to matter at our scale?