Left: a 1988 (possibly 1982) David Layzer-based entropy gap diagram, by American theoretical physicist Steven Frautschi, described as a: "schematic dependence of entropy S and maximum (equilibrium) energy Smax in the expanding universe"; such that the "gap" between the two line, Smax – S, represents the room for order in the universe, and that this is how life or intelligent order emerged in the context of the second law. [3] Right: a 2008 model version of the so-called entropy gap in the context of heat death theory, from the article “Life, Gravity and the Second Law of Thermodynamics” (figure 9), by Charles Linweaver and Chas Egan, captioned as: “The universe starts off at low entropy (not zero) due to the low level of density perturbations in the early universe—low Q and low A (e.g., [50])—where “low” means less than the maximum value Smax. At Smax all the energy density of the universe is in massless particles in equilibrium at a common temperature. Thus the universe starts off with a large entropy gap ΔS. The parameters Q and A are the observable normalizations of the primordial density fluctuations and set the initial gravitational entropy of the universe. There is no general agreement on the curve shown here. See for example Fig. 7.3 in [14] and Fig. 1.2 in [21].” [4] |

Frautschi-Layzer diagrams

Entropy-time diagrams that show entropy gaps, in attempts to argue some point, are called

In the 1988 book

Theory origin?

The "entropy gap" theory or argument seems to have originated in certain arguments in the 1975 "The Arrow of Time" by American astrophysicist David Layzer, although he does not use the actual term "entropy gap". Rather, following a near backwards convolution of information theory, statistical mechanics, arrow of time models, and big bang theory, he concludes: [7]

"The quantity of macroscopic information generated by the expansion [of the universe] is the difference between the actual value of the entropy and the theoretical maximum entropy at the mean temperature and density."

In 1982, American theoretical physicist Steven Frautschi cites the Layzer and gives a entropy gap type graph, shown adjacent, which seems to bee modeled on the above argument. American physicist Robert Doyle, likewise, in his 2003-launched InformationPhilosopher.com site, attributes the entropy gap graphical model to Layzer. [5]

The term "entropy gap" seems to have been first used in 1983 and promoted by those as physicists such as Roger Penrose, Paul Davies, and Brian Greene. Greene, for example, argues that the arrow of time points in the direction in which the entropy gap is being lessened. [2]

The following shows three entropy gap modes. Left: A 2011 summary of Layzer's 1975 entropy gap model of the universe, according to American physicist Robert Doyle. [9] Center: American physicist Victor Stenger's 2007 (possibly 2003)

In his 1983 book

“All life feeds off theentropy gapthat gravitation has created. The ultimate source of biological information and order is gravitation.”

(add discussion)

References

1. Davies, Paul. (1999).

2. Greene, Brian. (2004).

3. (a) Frautschi, Steven. (1982). “Entropy in an Expanding Universe”,

(b) Frautschi, Steven. (1988). “Entropy in an Expanding Universe”, in:

4. Lineweaver, Charles H. and Egan, Chas A. (2008). “Life, Gravity and the Second Law of Thermodynamics”,

5. Doyle, Bob. (2011).

6. (a) Stenger, Victor J. (2003).

(b) Stenger, Victor J. (2007).

7. Layzer, David. (1975). “The Arrow of Time”,

8. Davies, Paul. (1983).

9. Doyle, Bob. (2011).

10. Brooks, Daniel R. and Wilson, Edward O. (1988).

Further reading

● Al-Khalili, Jim. (1999).