This the long term end of the universe. It’s not really a disaster for the world as such as the world will have been long gone by the time this happens. It really depends on what we see in the universe being all there is. I suspect that there are other universes and the big bang may have been the result of a high power universe impinging on a low level universe, it expansion in this one just driven by the imbalance, going from high to low spacetime or timespace, expanding it like an inflating balloon. If this is what has happened then there may be other similar universes out there doing the same that we are not aware of, so we’re not all there is.
If we’re all there is, all we can do it keep outselves occupied until the end happens or everything simply falls apart.
If we aren’t all there is, then the object is to see how we can transfer to higher energy ones or transfer that energy to our own.
Entropy is the nature of our universe where there is a flow from higher energy to lower energy areas in a balancing out way, also going from a more organised state to a less organised state. The trend is nearly always in this direction, things decaying, getting old and collapsing. The only way to keep a stability is if there was a high entropy natural construction. Most things of lower entropy seeming to be constructs of natural fluctuations. Life in many ways is a fight against entropy, developing higher levels of organisation from lower level forms.
If you look at things like the Hubble Constant, the indications are that the universe will simply continue outwards and ‘run out of steam’ at some point and disperse into a flat energyless medium, completely dead. No stars, no galaxies and the planets, moons and asteroids similarly dispersing over its last moments. This is if the calculation we use for it are correct. I suspect we know a lot less that we think we do, dark energy and dark matter being terms for something that may not exist, but we need it for our equations and theories to work. Without these compensatory terms our equations and theories would need to be fundamentally wrong, which is what my guess would be.
Similarly with quantum mechanics, a lot of things today being claimed as happening purely because of it, but looking closely at many of them there were examples of them before the theory came along to explain them and they started being used or developed. For example semi-conductors. The first device using this principle was in 1874, but the principle was observed in 1833, the first double slit experiment being conducted in 1802 and black body radiation in 1860, Einstein’s theories being before and many at odds with quantum mechanics that developed in 1925. If you look at the progression of ideas and inventions there wasn’t a major and sudden jump after quantum mechanics was formulised, just a continuation of a steady amplifying flow that had been in force for over a hunbdred years. Quantum mechanics seemed to just be overlaid on what had gone on in the past.