Talk:Ultimate fate of the universe

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The Possibility of the Collapse of the Universe[edit]

The possibility arises, according to Stephen Hawking's 'The Beginning of Time' webpage at www.hawking.org.uk/the-beginning-of-time.html, that the No Boundary Proposal implies that the universe will Collapse. To quote Stephen Hawking "Because it [the no boundary proposal] requires that the universe is finite in space, as well as in imaginary time, it implies that the universe will re-collapse eventually. " Unfortunately, the Mathematical details of the No Boundary Proposal are not entirely clear to me (some sketch indications are verbally given upon the Hartle-Hawking state page where, for instance, it states that "The precise form of the Hartle–Hawking state is the path integral over all D-dimensional geometries that have the required induced metric on their boundary. ") The Hartle-Hawking state is related to the no boundary proposal - as it states that "Thus, the Hartle–Hawking state universe has no beginning, but it is not the steady state universe of Hoyle; it simply has no initial boundaries in time nor space.".

The issue of what would happen to the accumulated entropy of the collapsing universe is something that is worthy of consideration. Stephen Hawking states : "The universe will get more and more lumpy and irregular, as it gets smaller, and disorder will increase."

So the Second Law of Thermodynamics doesn't get contravened - or so it appears. ASavantDude (talk) 19:08, 19 October 2017 (UTC)

An eternally expanding Universe[edit]

There may be strong consensus amongst cosmologists arguing that the universe is "flat" and will continued to "expand forever". However, it seems unlikely that such clear consensus can be agreed. There are, for instance, theories such as Quintessence that argue that "quintessence can be either attractive or repulsive" - which, presumably, allows for some cyclic cosmology.

The key issue ought to relate to what is true concerning the best scientific theory, and not just what the consensus states.

ASavantDude (talk) 16:31, 6 June 2018 (UTC)

Continuing on from above. If the truth is not known concerning the ultimate fate of the universe (for instance, the universe is said to be flat within a certain percentage of error - but this does not preclude the possibility that the universe might have slightly positive, or negative, curvature and this has an impact upon the ultimate fate of the universe), then this should be clearly stated. That is, that the truth concerning the ultimate fate of the universe is still highly speculative. There are many other issues worth raising, such as what enables a theory to be 'true' insofar as Popper's falsificationism goes, and whether notions of falsificationism are affected in any way by quantum phenomena. I note that the 'Shape of the Universe' pages states that "the observable universe is flat with only a 0.4% margin of error.", this does not preclude the possibility that the universe is not flat (nor does it indicate what the sources of the 0.4% margin of error actually are). I will look into the matter more.

ASavantDude (talk) 09:20, 18 June 2018 (UTC)

What would Stephen Hawkings say?[edit]

According to : http://www.hawking.org.uk/the-beginning-of-time.html "What does the no boundary proposal predict for the future of the universe? Because it requires that the universe is finite in space, as well as in imaginary time, it implies that the universe will re-collapse eventually. However, it will not re-collapse for a very long time, much longer than the 15 billion years it has already been expanding."

So Stephen Hawking clearly believed re-collapse follows theoretically from one of his theories (arguably a major theory of his). I do not know what experimental observations the no boundary theory makes, but it is possible that Hawking's theories are compatible with a cyclic model of the universe.

ASavantDude (talk) 15:22, 19 June 2018 (UTC)

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