Asked by: Jamie Edwards, Essex
Yes. This relic radiation left over from the Big Bang is being increasingly redshifted as the Universe expands. So its energy is being constantly diluted.
After another few trillion years, the current cosmic microwave background will have redshifted into insignificance and will no longer be detectable. In this far-flung future, the Universe will have expanded so much that even the closest galaxies will be well beyond our sight. At this time, there will be no visible evidence that the Universe is expanding or that there was ever a Big Bang!