RE: A fined tuned argument.....Heywood style.
March 27, 2014 at 4:21 am
(This post was last modified: March 27, 2014 at 4:35 am by Alex K.)
I don't do argumentum ad youtubum, so I reply anyways.
Your fine tuning argument is at least more coherent than your argument against naturalistic evolution, which is just... anyways, I digress.
It is true that changing several physical parameters in the Standard Model and Gravity could lead to a universe in which there is very little structure (no chemistry and stars etc.) or which would live only for a very short time.
A few comments:
* You have a philosophical problem to begin with: if you claim that a universe with apparently fine-tuned parameters has a problem that needs explaining, you somehow have to assume that it could have been differently - but from which set of possible universes is ours chosen, and with what mechanism, in absence of proposition A or B. You therefore have to state much more clearly why indeed you think fine-tuning is a problem. Please elaborate on this point, in particular what you mean by poss. D.
* It is not the cosmological constant itself which must be chosen with such precision. If you change the observed cosmological constant by a few percent, nothing radical would change in the universe. The numbers you quote come from a theoretical problem in coupling the Standard Model of Particle Physics to General Relativity: when one does that, the cosmological constant receives very large contributions from virtual particles which raise the energy level of the quantum vacuum. One then has to counterbalance this large quantum contribution with a fine tuned cosmological constant parameter in the opposite direction which cancels this contribution from virtual particles to very high accuracy - in the extreme case to something like the degree you quote above (I haven't counted the trillions and trillions). Your argument is significantly weakened by the fact that this is not a fine tuning in observed parameters, but in theoretical input parameters, which are meaningless if we find a more consistent way to couple quantum theory to gravity - a not very controversial proposition considering that we do not have a definite self-consistent theory of quantum gravity which is tested. This is an important reminder that input parameters in quantum field theory are not observable quantities with direct physical meaning.
* Even if I accept all your premises, we don't get 50% each by a looong shot. This is because for those two propositions, observations very strongly favor B over A: The Universe looks exactly as you would expect an anthropically selected universe to look: if you have a priori probability distributions with strong dependences on the parameters, you expect to have many parameters of your theory pushed towards catastrophic boundaries, but barely on the anthropically favored side. Here's a published paper where this is explained:
http://arxiv.org/pdf/1005.2783.pdf
If the universe were designed for life, we would precisely not be living on the edge in so many ways. You unwittingly killed your proposition A with the fine-tuning argument: if you work that bayesian magic and carry through honestly the expectations vs. observations from possibilities A and B with equal priors, you end up with a tiny posterior for proposition God, and nearly 1 for proposition Multiverse.
Your fine tuning argument is at least more coherent than your argument against naturalistic evolution, which is just... anyways, I digress.
It is true that changing several physical parameters in the Standard Model and Gravity could lead to a universe in which there is very little structure (no chemistry and stars etc.) or which would live only for a very short time.
A few comments:
* You have a philosophical problem to begin with: if you claim that a universe with apparently fine-tuned parameters has a problem that needs explaining, you somehow have to assume that it could have been differently - but from which set of possible universes is ours chosen, and with what mechanism, in absence of proposition A or B. You therefore have to state much more clearly why indeed you think fine-tuning is a problem. Please elaborate on this point, in particular what you mean by poss. D.
* It is not the cosmological constant itself which must be chosen with such precision. If you change the observed cosmological constant by a few percent, nothing radical would change in the universe. The numbers you quote come from a theoretical problem in coupling the Standard Model of Particle Physics to General Relativity: when one does that, the cosmological constant receives very large contributions from virtual particles which raise the energy level of the quantum vacuum. One then has to counterbalance this large quantum contribution with a fine tuned cosmological constant parameter in the opposite direction which cancels this contribution from virtual particles to very high accuracy - in the extreme case to something like the degree you quote above (I haven't counted the trillions and trillions). Your argument is significantly weakened by the fact that this is not a fine tuning in observed parameters, but in theoretical input parameters, which are meaningless if we find a more consistent way to couple quantum theory to gravity - a not very controversial proposition considering that we do not have a definite self-consistent theory of quantum gravity which is tested. This is an important reminder that input parameters in quantum field theory are not observable quantities with direct physical meaning.
* Even if I accept all your premises, we don't get 50% each by a looong shot. This is because for those two propositions, observations very strongly favor B over A: The Universe looks exactly as you would expect an anthropically selected universe to look: if you have a priori probability distributions with strong dependences on the parameters, you expect to have many parameters of your theory pushed towards catastrophic boundaries, but barely on the anthropically favored side. Here's a published paper where this is explained:
http://arxiv.org/pdf/1005.2783.pdf
If the universe were designed for life, we would precisely not be living on the edge in so many ways. You unwittingly killed your proposition A with the fine-tuning argument: if you work that bayesian magic and carry through honestly the expectations vs. observations from possibilities A and B with equal priors, you end up with a tiny posterior for proposition God, and nearly 1 for proposition Multiverse.
