47. EXPANDING UNIVERSE

The future of the universe is a continuous and intriguent question, sofar without any definitive answer. But there many models giving more or less acceptable solutions.
The "collapsing model": which requires a strong density, much higher than the critical density, leading to a "big crunch", but that is in contradiction with all the data.
The "pure matter model" : requiring sufficient real matter in the universe, what certainly is not the case, it should lead to a rather constant expansion of the universe.
The "cosmological constant model": Einsteins' idea, based on the famous"vacuümenergy", it leads to a constant accelerated expansion of the universe. It means a more and more empty universe expanding for ever, an anathema for astronomers.
The "quintessence model":
The essential feature of this theory is the supposed dynamic of the quintessence field, in fact a quantumfield (scalarfield), what gives an acceptable explanation both for the inflation and the evolution of the universe, particularly for the fast expansion over the last billions years, including a solution for the difference in measured and calculated density. Anyhow, the theory requires the questionable Dark Energy (= vacuüm energy).
Another consequence of the theory is that there will be an ending to the condensation of matter, that is the creation of new stars and starsystems, the density of matter will continuously decrease and maybe the acceleration of the expansion will increase. But it is also possible be that with a declining quintessencefield new forms of radiation and dustforming evolve in creating and expanding “bubbles” of “empty space”, of which the envelopes absorb still more energy, what then can be the cause of the formation of new forms of protons and neutrons and perhaps, finally, stars and starsystems and perhaps life.
A nice predictive theory, but yet with many suppositions still to be proved.