Dear all, I have been reading Wonders of the Universe by Prof. Brian Cox. I enjoyed the TV programs and thought the book would also be interesting, which it is. In the last chapter of the book, and also discussed in the TV program, it talks about the end of the Universe in many trillions of years time. What is put forward is that black holes will evaporate and that all remaining matter will decay into photons. These photons will then be stretched by the expanding universe until they no longer have any energy as they reach absolute zero, at which point all energy in the universe will have been returned to the vacuum. I have a slightly different thought which I wanted to get feedback on. I’m OK with the evaporating black holes but to date there is no evidence that protons, electrons and neutrons have a half life and can therefore decay to give rise to the proposed end of the universe as mentioned above. Is it therefore at all possible that if matter cannot or does not decay that the following mechanism to return energy to the vacuum can occur. Black holes evaporate and all remaining matter will cool to absolute zero. At this point all matter, and photons for that matter will form a Bose-Einstein condensate and the energy of the universe will then be returned to vacuum. There is another post related to this on this forum with out any replies - Questions on Einstein Bose condensate and end of Universe. I would be happy to hear others people thoughts on this as a mechanism to return energy to the vacuum. Cheers, Dale79J.