The Origins of the Laws of Nature

Bengt Gustafsson:

Current problems in Astrophysics

Lecture 5

Ångström Laboratory, Spring 2010

Reading:

Carter, (1974): Large Number Coincidences and the Anthropic Principle in Cosmology, IAU Symp. 63, 291

Carr & Rees (1979): The Anthropic Principle and the structure of the physical world, Nature 278, 605

Barrow & Tipler (1988): The Anthropic Cosmological Principle, Oxford Univ. Press

Jaffe et al. (2009): Quark Masses: An Environmental Impact Statement, Phys. Rev. D. 79, 5014

Tegmark (1998): Is the theory of everything merely the ultimate ensemble theory, Annals of Physics 270, 1

Davies (2006): The Goldilocks Dilemma, Allen Lane

Further references, see Wikipedia: Anthropic principle

Why is the Universe as it is?A meaningful question in physical science??

Cf ”ignorabimus” -debate (late 19th century)

”What really interests me is if God had any choice in the creation of the World”

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Why is the universe so old?

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P. Dirac (1937):Why is the present age of the universe~ electron time scale h/(mec2)divided by G = Gmp

2/hc (gravitational fine-structure constant? R. Dicke (1961): Least possible age of stars to produceenough carbon to ”make physicists”~ G

-1 h/(mec2) ~ 1010 years.

”Natural explanation” for Dirac’s”coincidence”

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Could the world have been different?

• If we wish to understand why the world is as it is, the existence of observers must be taken into consideration

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Brandon Carter

”weak”: location -- in space time”strong”: constants, laws of nature

”Anthropic Principle”

Other examples

12C nuclear structure: Resonance at 7.7 MeVF. Hoyle (1954)

Strong interaction: ±10%

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Several examples from

Stellar evolution and Planetary system formation etc in paper by Carr and Rees (1979), and book by Barrow & Tipler (1988)

E.g. conditions for convective, but not allthrough convectivce stars:

G ~ 20 (fine structure constant = e2/hc) G larger => all stars radiative blue stars, G smaller all stars

red dwarfs with full mixing.

Condition for neutrinos to blow off SN envelope: G ~ W4 (W

= gme2c/h3). W slightly smaller => all H He in Big

Bang.

Further examples

• Cosmology:

- speed in expansion and isotropy (Collins & Hawking

1973), c.f. inflation

- cosmological constant (Weinberg 1987)

- string landscape (Susskind 2003)

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> 10700 worlds?

Further examples

• Moon (tides, convection in Earth?)

• Jupiter (water on Earth)

• Grav ~ 1/r2

• 3 space dimensions

• Ice density

• …

Formulations by Barrow and Tipler (1986)

• WP: The observed values of all physical and cosmological quantities are not equally probable but take their values restricted by the requirement that there exist sites where carbon-based life can evolve and by the requirement that

the Universe be old enough for it to have already done so.” • SP: ”The universe must have those properties which

allow life to develop within it at some stage in history.”

Are observers necessary for ”the existence” of the Universe?

”Observers are necessary to bring the Universe into being”

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John A. Wheeler

Criticisms:• Empty statements -- truisms or tautologies.• Not fasifiable• Teolological, Aristotelian, ad posteriori. Cause and

effect reversed (Stephen Jay Gould, Michael Shermer)• ”Anthropic” misleading. ”Carbon chauvinism”.

Just complexity?• ”Principle” misleading. Selection effects.• SAP discourages searches for physical explanations.

”It tends to be invoked by theorists whenever they do not have a good enough theory to explain the observedfacts” (Penrose)

• ”Just-so-stories” - lowered level of ambition in scientific explanation.

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The best of worlds?

• Leibniz: Theodicée (1710).

• Voltire (Candide):

”Please, note that noses are made to carry glasses, thus we wear glasses. Feet are obviously created to have shoes, thus we wear shoes. Stones are formed to be cut to building blocks in castles, thus Your Grace has such a beautiful castle.”

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Many-world theories

• Nicolaus Cusanus (1401-1464)

• Hugh Everett ( 1956)

• Wheeler (1960)

• String landscape …QuickTime och en

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Andrei Linde: Chaotic inflation

”So much in vain”(Martin Rees)

More criticims

• Not falsifiable (”Do we see them?”)

• Inifinity not necessarily = all possible worlds

Recent developments

• Mapping what worlds could be there:

Jaffe et al. (2009): Could 12C form with other quark masses? (u, d, s).

md ~2 mu (mn ~ 1.001mp)

<

Recent developments

• Mapping what worlds could be there:

Jaffe et al. (2009): Could 12C form with other quark masses? (u, d, s).

md ~2 mu (mn ~ 1.001mp)

1H no longer stable, but 2H and 3H might be as well as 14C.

< 0.99

Can a ”weak less” universe give life?

• Jenkins, Perez, LBNL group (2010):

p+p reactions impossible

Small ajustment of matter/antimatter ratio

=> 2H in BB.

Stars could shine by 2H+p 3He + and further nucleosynthesis possible.

Counterfactual history, also sometimes referred to as virtual history, is a recen form of historiography which attempts to answer "what if" questions known as counterfactuals. It seeks to explore history and historical incidents by means of extrapolating a timeline in which certain key historical events did not happen or had an outcome which was different from that which did in fact occur.The purpose of this exercise is to ascertain the relativeimportance of the event, incident or person the counterfactual hypothesis is negating. For instance, to the counterfactual claim "What would have happened had Hitler drunk coffee instead of tea on the afternoon he committed suicide?", the timeline would have remained unchanged — Hitler in all likelihood still would have committed suicide on April 30, 1945, regardless of what he had to drink that afternoon. However, to the counterfactual "What would have happened had Hitler died in the July, 1944, assassination attempt?", all sorts of possibilities become readily apparent, starting with the reasonable assumption that the German generals would have in all likelihood sued for peace, bringing an early end to World War II, at least in the European Theater. Thus, the counterfactual brings into sharp relief the importance of Hitler as an individual and how his personal fate shaped the course of the war and, ultimately, of world history.