Quote from jcl:
Again, Penrose means a different thing. He refers to the solutions of string theory, and calls each solution a "universe". This is not the multiverse. The number of string theory solutions is high, but finite.
Multiple universes would exist even if the theory had only one solution. They are generated from the brane dynamics of the 11 dimensional space our universe is embedded in, according to string theory. Their number must be infinite because the generating space and time is not finite. The multiverse model was developed by Gabriele Venenziano, one of the fathers of string theory. It is not conjecture, but based on solid mathematics. You can look it up in the Internet.
Although Penrose talks about multiple universes and fine tuning, he means something entirely different, and this may be confusing. You must understand the context.
I don't know where you got this number from, but you must have misunderstood something. The cosmological constant can be derived from the Hubble constant, which is only known today with an accuracy of about 2%. Therefore calculating a precision of 10^53 for it is nonsense. No physical constant today can be estimated with this precision. Besides, the cosmological constant just determines the life time of our universe, and it has a relatively wide range within life can evolve. Fine tuning mostly limits other constants, such as light speed, Planck's constant etc.
1. weinberg gave us the 10 to the 53. Its posted here on et dozens of times.
2. Penrose on video argues the multiverse idea is not enough to explain the fine tuning. Could you provide links to what you say Penrose is saying.
3. regarding the history of string theory and the multiverse conjecture...
we discussed this on ET from right about the time Susskind released his book.
I argued that Susskind was saying our universe appeared designed and Stu and typical ET atheist clowns argued I was wrong.
http://www.nytimes.com/2006/01/15/b...w/15powell.html
Although string theory resists translation into ordinary language, its central conceit boils down to this: All the different particles and forces in the universe are composed of wriggling strands of energy whose properties depend solely on the mode of their vibration. Understand the properties of those strands, the thinking once went, and you will understand why the universe is the way it is. Recent work, most notably by Joseph Polchinski of the University of California, Santa Barbara, has dashed that hope. The latest version of string theory (now rechristened M-theory for reasons that even the founder of M-theory cannot explain) does not yield a single model of physics. Rather, it yields a gargantuan number of models: about 10500, give or take a few trillion.
Not one to despair over lemons, Susskind finds lemonade in that insane-sounding result. He proposes that those 10500 possibilities represent not a flaw in string theory but a profound insight into the nature of reality. Each potential model, he suggests, corresponds to an actual place - another universe as real as our own. In the spirit of kooky science and good science fiction, he coins new names to go with these new possibilities. He calls the enormous range of environments governed by all the possible laws of physics the "Landscape." The near-infinite collection of pocket universes described by those various laws becomes the "megaverse."
Susskind eagerly embraces the megaverse interpretation because it offers a way to blow right through the intelligent design challenge...
we have been discussing this here on ET since Susskind wrote the book and explained he waited for polchinsky's math before he put forth the conjecture that all the solutions were universes.
I will give you some background on the multiverse conjecture.
