Cosmic microwave background © Getty Images

Will the cosmic microwave background disappear?

The cosmic microwave background (CMB) is radiation left over from the Big Bang.

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!


Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.