Anthropic PrincipleGaurav HarshaII year, Physical Sciences

Is It A Coincidence?

• The ratio of the electromagnetic force to the gravitational force between two electrons is a large number N1=1039. Why not another number?

• The estimated number of particles, called as the “Eddington Number” N=1079. This number is not far from the square of N1.

• The neutron is heavier than proton, but the difference is not much. Also, the mass of electron is less than the difference in masses of neutron and proton.

• The vacuum energy density of the universe is at least 120 orders of magnitude lower than some theoretical estimates.

The Anthropic Principle

• Proposed by Brandon Carter, in 1973, during a synopsis commemorating Copernicus’s 500th birthday.

• Carter: “Humanity did indeed hold a special place in the universe”, an assertion exactly opposite to Copernicus’s.

• There are two forms of the Anthropic Principle

– Weak Anthropic Principle

– Strong Anthropic Principle

Weak Anthropic Principle

• In word of Dr. Stephen Hawking:

“We see the universe the way it is because we exist”

• As proposed by mathematician John Barrow and physicist Frank Tipler, WAP reads:

“The observed values of all physical and cosmological quantities are not equally probable but take on values

restricted by the requirement that there exists sites where carbon-based life form can evolve and by the requirement that the Universe be old enough for it to have already done

so.”

Anthropic Coincidences

• The ratio of the electromagnetic force to the gravitational force between two electrons is a large number N1=1039. Why not another number?

• The mass of electron is less than the difference in masses of neutron and proton.

• The neutron is heavier than proton, but the difference is not much.

• The vacuum energy density of the universe is at least 120 orders of magnitude lower than some theoretical estimates.

Use WAP

• If the Electromagnetic to the Gravitational force between two electrons were more comparable, stars would have collapsed long before life had a chance to evolve.

• Mass of e-- :

• Stable neutron will mean no proton and electron, i.e., no hydrogen fuel for the stars.

• If neutron is little more heavier than it is in our world, they cannot bound in nuclei, where conservations of energy prevents neutron decay. So, NO HEAVY ELEMENTS, NO LIFE.

• The vacuum energy density: if it was higher, the universe would have quickly blown apart. If it was much less, it would have collapsed into a big crunch before evolution of life.

• ICE FLOATS ON WATER!!

Age of Universe

• 14.6 billion years. Why not 1.46??

• It takes about that long for intelligent beings (us) to evolve.

Triple Alpha Process

• How does Carbon form in stars?

• Theories till 1950’s suggested that Be8 and He4 nuclei undergo fusion to form C12.

• The problem is that Be8 is very unstable with a time period of only 10-17 s.

• Fred Hoyle, in 1957, suggested that the rapid collision between three alpha particles can lead to formation of C12 provided that there exists a resonance state of C12 that is equal to the energy of incoming alpha particle and the ground state Be8. Hence, the probability of C12 formation increases.

Strong Anthopic Principle

“The Universe must have those properties which allow life to develop within it at some stage in its history”

And if you accept SAP, then the Final Anthropic Principle becomes a logical conclusion (as stated by Barrow and Tipler):

“Intelligent, information processing must come into evidence in in the Universe, and, once it comes into existence, it will

never die out”

Arguments Against SAP

• If separate universes, then what happens in one universe does not have any effects on another. So, use the principle of economy.

• If regions of same universe, then for continuity laws of science should remain same, hence the only difference is the initial configurations. SAP becomes WAP.

• The Multiple Worlds cosmology claims a more scientific alternative to Anthropic Principle.

• The Baby Universe theory is even more outlandish.

References

• A Brief History of Time by Stephen Hawking

• The Anthropic Cosmological Principle by John Barrow and Frank Tipler

• The Anthropic Principle by Victor J. Stenger for The Encyclopedia of Nonbeliefs.

• Wikipedia: www.wikipedia.org

• San Francisco State University web material:

http://www.physics.sfsu.edu/~lwilliam/sota/anth/anthropic_principle_index.html