Re: The beginning?

As with interpretations of what happened in the very early universe, advances in fundamental physics are required before it will be possible to know the ultimate fate of the universe with any certainty. Below are some of the main possibilities.

Fate of the Solar system: 1 to 5 billion years [edit]Main articles: Formation and evolution of the Solar System#Future, Stability of the Solar System, Future of the Earth#Solar evolution, and Red giant#The Sun as a red giant Relative size of our Sun as it is now (inset) compared to its estimated future size as a red giant

Over a timescale of a billion years or more, the Earth and Solar System are unstable. Earth's existi...biosphere is expected to vanish in about a billion years, as the Sun's heat production gradually inc...[19] the Earth's magnetic fields, axial tilt and atmosphere are subject to long term change; and the...chaotic over million- and billion-year timescales;[20] Eventually in around 5.4 billion years from now, the core of the Sun will become hot enough to ...[19] This will cause the outer layers of the star to expand greatly, and the star will enter a phase...red giant.[21][22] Within 7.5 billion years, the Sun will have expanded to a radius of 1.2 AU—256 times its curren...tidal interaction between Sun and Earth, Earth would actually fall back into a lower orbit, and get ...[23] The Sun itself will continue to exist for many billions of years, passing through a number of phases, and eventually (if nothing else changes) ending up as a long-lived white dwarf. Eventually, after billions more years, the Sun will finally cease to shine altogether, ...black dwarf.[24]

Big freeze: 1014 years and beyond [edit]Main articles: Future of an expanding universe and Heat death of the universe

This scenario is generally considered to be the most likely,[citation needed] as it occurs if the universe continues expanding as it has been. Over a time scale on the order of...stars burn out, stars cease to be created, and the universe goes dark.[25], §IID. Over a much longer time scale in the eras following this, the galaxy evaporates as the stellar remnants comprising it escape into space, and black holes evaporate via Hawking radiation.[25], §III, §IVG. In some grand unified theories, proton decay after at least 1034 years will convert the remaining interstellar gas and stellar remna...[25], §IV, §VF. In this case, the universe has reached a high-entropy state consisting of a bath of particles and low-energy radiation. It is not known however wh...thermodynamic equilibrium.[25], §VIB, VID.

Big Crunch: 100+ billion years from now [edit]See also: Big Crunch

If the energy density of dark energy were negative or the universe were closed, then it would be possible that the expansion of the universe would reverse and the universe ...oscillatory universe scenarios, such as the cyclic model, although a Big Crunch does not necessarily imply an oscillatory Universe. Current obse...

Big Rip: 20+ billion years from now [edit]See also: Big Rip

This scenario is possible only if the energy density of dark energy actually increases without limit over time.[citation needed] Such dark energy is called phantom energy and is unlike any known kind of energy. In this case, the expansion rate of the unive...gravitational singularity. At the time of this singul