* Astronomy

Members Login
Username 
 
Password 
    Remember Me  
Home -> Astronomy News -> Videos -> Anthropic principle
Post Info
TOPIC: Anthropic principle
Blobrana


L

Posts: 131433
Date:
RE: Anthropic principle
Permalink  
 

Life in the Universe

What we normally think of as 'life' is based on chains of carbon atoms, with a few other atoms, such as nitrogen or phosphorous. One can speculate that one might have life with some other chemical basis, such as silicon, but carbon seems the most favourable case, because it has the richest chemistry. That carbon atoms should exist at all, with the properties that they have, requires a fine adjustment of physical constants, such as the QCD scale, the electric charge, and even the dimension of space-time.
If these constants had significantly different values, either the nucleus of the carbon atom would not be stable, or the electrons would collapse in on the nucleus. At first sight, it seems remarkable that the universe is so finely tuned. Maybe this is evidence, that the universe was specially designed to produce the human race. However, one has to be careful about such arguments, because of what is known as the Anthropic Principle. This is based on the self-evident truth, that if the universe had not been suitable for life, we wouldn't be asking why it is so finely adjusted. One can apply the Anthropic Principle, in either its Strong, or Weak, versions.
For the Strong Anthropic Principle, one supposes that there are many different universes, each with different values of the physical constants. In a small number, the values will allow the existence of objects like carbon atoms, which can act as the building blocks of living systems. Since we must live in one of these universes, we should not be surprised that the physical constants are finely tuned. If they weren't, we wouldn't be here. The strong form of the Anthropic Principle is not very satisfactory.
What operational meaning can one give to the existence of all those other universes? And if they are separate from our own universe, how can what happens in them, affect our universe. Instead, I shall adopt what is known as the Weak Anthropic Principle. That is, I shall take the values of the physical constants, as given. But I shall see what conclusions can be drawn, from the fact that life exists on this planet, at this stage in the history of the universe.
Read more



__________________
Blobrana


L

Posts: 131433
Date:
Permalink  
 

Title: Axions, Inflation and the Anthropic Principle
Authors: Katherine J. Mack
(3 Nov 2009)

The QCD axion is the leading solution to the strong-CP problem, a dark matter candidate, and a possible result of string theory compactifications. However, for axions produced before inflation, symmetry-breaking scales of f_a \gtrsim 10^{12} GeV (which are favoured in string-theoretic axion models) are ruled out by cosmological constraints unless both the axion misalignment angle \theta_0 and the inflationary Hubble scale H_I are extremely fine-tuned. We show that attempting to accommodate a high-f_a axion in inflationary cosmology leads to a fine-tuning problem that is worse than the strong-CP problem the axion was originally invented to solve. We also show that this problem remains unresolved by anthropic selection arguments commonly applied to the high-f_a axion scenario.

Read more  (1288kb, PDF)



__________________
Blobrana


L

Posts: 131433
Date:
Permalink  
 

A controversial idea from the early 80's is again being disputed
Astronomers continue the hunt for signs of intelligent life away from Earth, and a new study aims to refute a controversial theory that claims extraterrestrial intelligence is rare because of how long it takes intelligent life to evolve.
Astrobiologist Milan Cirkovic and several other researchers found a flaw in the anthropic argument, noting that Brandon Carter, who proposed the Anthropic argument, worked on the assumption that the life cycle of a star and evolution worked on two different timelines.  Cirkovic, however, believes the timelines are entwined and need one another.

Read more

__________________
Blobrana


L

Posts: 131433
Date:
Permalink  
 

Life May Depend on Galaxy
Intelligent life beyond Earth might not be as dim a hope as many scientists think, according to a new study challenging a widely held anti-ET argument.
Many skeptics tout an idea called the anthropic argument that claims extraterrestrial intelligence must be very rare because the time it takes for intelligent life to evolve is, on the average, much longer than the portion of a star's existence that is conducive to such life.
But now astrobiologist Milan M. Cirkovic and colleagues say they've found a flaw in that reasoning.

Read more

-- Edited by Blobrana on Thursday 13th of August 2009 03:20:17 PM

__________________
Blobrana


L

Posts: 131433
Date:
Permalink  
 

Life in a fine-tuned Universe - Part 1
Life in a fine-tuned Universe - Part 2
Life in a fine-tuned Universe - Part 3
Life in a fine-tuned Universe - Part 4
Life in a fine-tuned Universe - Part 5



__________________
Page 1 of 1  sorted by
 
Quick Reply

Please log in to post quick replies.
Home -> Astronomy News -> Videos -> Anthropic principle


Create your own FREE Forum
Report Abuse 		Powered by ActiveBoard