Talk:Entropy as an arrow of time

Some thoughts

This article asks why the universe began with low entropy.

But heat death of the universe says this: "Recent work in inflationary cosmology has inverted the heat death notion, suggesting that the early universe was in a thermal equilibrium and thus heat death–like state before cosmic expansion. Meanwhile, in an expanding universe, some believe the maximum possible entropy increases far more quickly than the actual entropy with each time increment, pushing the universe continually further away from an equilibrium state despite increasing entropy. Furthermore, the very notion of thermodynamic modelling of the universe has been questioned, since the effects of such factors as gravity and quantum phenomena are very difficult to reconcile with simple thermodynamic models, rendering the utility of such models as predictive systems highly doubtful according to some."

In what sense did the universe begin at minimal entropy, if entropy is defined as thermal equillibrium?

Oneismany 08:55, 3 May 2006 (UTC)[reply]

Entropy's pretty fucked up, eh?

--Davidknippers 06:59, 12 May 2006 (UTC)[reply]

To answer the above question, the early universe is not considered to have been at minimal entropy, because its spectral distribution was that of a black-body (and consequently at thermal equilibrium.)

Tkircher 05:40, 30 July 2006 (UTC)[reply]

Oh my

"An equivalent way of saying this is that the information possessed by the demon on which atoms are considered "fast" or "slow", can be considered a form of entropy known as information entropy."

wtfhax

Three scenarios

The three scenairios at the end of the article miss the fact that the universe most likely is not expanding. Einstein's theory with conservation of energy, as opposed to the Big Bang, predicts Hubble constant as it is observed (accelerating with acceleration 2.5E-36 1/s2). From it predicts the density of the universe (6.5E-27 kg/m3), acceleration of space probes (7E-10 m/s2), the size of pieces of non luminous matter (1 m). It predicts also distances to some quasars. Usually when theory predicts so many things right and none wrong it is worth looking into it, especially when it is created by Einstein. Jim 19:43, 18 June 2006 (UTC)[reply]

Change of name of article

FYI, I am contemplating moving this article to arrow of time (physics) and possibly spitting it into several articles. I admit I am prejudiced: I think that cosmological explanations for the arrow of time are teleological hogwash, right up there with the work of the Bogdanov brothers. Also, entropy does have something to do with it, but this article fails to sketch this correctly. linas 15:47, 2 August 2006 (UTC)[reply]

Starting arrow of time (physics) sounds like it might be a reasonable idea as long as you reference it as it is discussed in physics books; however moving this article doesn’t make any sense. I was the one who moved it here in the first place. The entropy page was getting too long; see: Talk:Entropy/Archive2#Article is now 46 kilobytes long (the limit is 32) for a discussion of this. Moreover, as far as I am aware of, the term “arrow of time” was first used by Arthur Eddington in his 1928 discussions about “entropy”, see for example pgs. 69-88 and 295 in Eddington’s book The Nature of the Physical World. Hence the name of the article entropy (arrow of time).

As this book was written in a lose tone (without equations) for philosophers and for the general public, the idea spread rapidly from here. Harold Blum’s 1950 Time’s Arrow and Evolution cites Eddington’s 1927 book as the source of the term, as based on the argument that the second law of thermodynamics, i.e. the law that energetically quantifies the phenomenon of irreversibility, points in the direction of all real events in time.

Certainly, cleaning, removing teleological references, and reshuffling things, etc. or even starting a new article, such as arrow of time (physics), or even a new category, i.e. category:arrow of time, may be in order, but moving the article is bad idea – entropy is the arrow of time as it was originally defined by Eddington. Thanks:--Sadi Carnot 18:12, 2 August 2006 (UTC)[reply]