continued from above:
ALso plenty of scientists find the many world's interpretation to be reasonable and have some evidence.
Actually, nobody could possibly have any evidence for the MWI specifically, as all the evidence comes from quantum mechanics, which means that it exists for every interpretation. Plenty of scientists find it preferable to alternative interpretations for ideological reasons, but this is now metaphysics. And as such, it is no more empirical or scientific than theology.
Arguing from authority that Penrose is critical isn't persuasive.
But repeating that “many scientists find X” to be the case is supposed to be?
Anyway, it's not meant to persuade, but to explain the epistemological foundations for such cosmologies and their problems. They all involve not only highly speculative metaphysics and derivations based on mathematical aesthetics rather than any empirical findings or even a consequence of such findings. Inflationary cosmologies are mathematical solutions to issues that are metaphysical and ideological in nature (on the mathematical foundations in relationship to the theory see e.g., Mitra, A. (2014). Why the Big Bang Model does not allow inflationary and cyclic cosmologies though mathematically one can obtain any model with favourable assumptions.
New Astronomy,
30, 46-50.). There is nothing empirically problematic in physical cosmology that necessitates or even suggests the possibility of inflationary models ("The standard big bang (SBB) model has a number of puzzles, particularly the so-called horizon and flatness problems, which are believed to require explanation and not just be accepted by fiat"; Coule, D. H. (2000). Quantum creation and inflationary universes: A critical appraisal.
Physical Review D,
62(12), 124010.)
In fact, what empirical evidence exists that is supposed to merit inflationary models has now proved to make inflation a problem rather than a solution:
Ijjas, A., Steinhardt, P. J., & Loeb, A. (2013). Inflationary paradigm in trouble after Planck2013.
Physics Letters B,
723(4), 261-266.
&
"Ultimately, the result is an eternal multiverse in which “anything can happen and will happen an infinite number of times”. What does inflation predict to be the most likely outcome in the multiverse?...the volume-weighted prediction is that our observable universe is exponentially unlikely by a factor exceeding 10^−10^55 or more!
Classic inflation is a catastrophic failure by this measure; numerically, it is one of the worst failures in the history of science.
How has a theory that fails catastrophically continued to survive in scientific discourse?" (emphasis added)
Ijjas, A., Steinhardt, P. J., & Loeb, A. (2014). Inflationary schism.
Physics Letters B,
736, 142-146.
Luckily, we don't need to be debating whether or not inflationary models are ultimately supportable or even scientific. This is because regardless of whether or not one is a supporter of inflation, the evidence and reasons for the proposal remain the same: it is supposed to solve problems that are only problems granted certain aesthetic and metaphysical assumptions. The solution is a mathematical derivation that cannot be tested apart from the assumptions made to motivate the models in the first place (i.e., we can empirically investigate e.g., the so-called "flatness problem" but whether inflation presents a fix for such issues remains a philosophical or metaphysical matter that is only supportable to the extent it is actually a "fix" and the problem is actually a problem, which again isn't an empirical matter but an ideological one).
Inflationary theory does have predictive power and can be tested by determining inflation's effect on the CMB.
What does it predict?
It isn't just mathematical guesswork
It's a set of models that result from a mathematical derivation.
Nobody is explaining anything by defining the result to be true.
Nobody except physicists and cosmologists. Again, the most succinct expression of this fact comes from Carr's introductory essay in the volume for and by specialists cited above on the issue of the multiverse:
"To the hard-line physicist, the multiverse may not be entirely respectable, but it is at least preferable to invoking a Creator.
Indeed anthropically inclined physicists like Susskind and Weinberg are attracted to the multiverse precisely because it seems to dispense with God as the explanation of cosmic design" (emphases added)
from the editor's introduction to Carr, B. (Ed.). (2007).
Universe or multiverse?. Cambridge University Press.
An infinite number of universes would indeed explain the particular values that constants have since every possible permutation of constants would exist.
Wrong. First you are wrong because technically the constants aren't permuted: it's called tuning for a reason (they have values) and even if we set the number of parameters equal to that of the standard model, we wouldn't be permuting them.
Second, and far more importantly, a countably infinite number of universes could not contain the set of all possible universes in which the values of a single constant changed by any real-valued number less than 0.0000000000001 (there are uncountably infinitely many real numbers in every interval).
Your analogy is inappropriate.
I didn't make an analogy. I claimed that defining the multiverse into existence to "solve" the fine-tuning problem isn't an explanation. Here's an analogy: The probability of winning the lottery is tiny, but (at least for some lotteries) there is necessarily a winner. So the fact that some improbable result happens here is explained by the fact that even though the specific individual need not have won, someone had to. Likewise, with an infinite number of universes, we can state simply that we were the lottery winners. The problem is that the only reason to suppose there was a lottery to begin with (i.e., that there are infinitely many universes and we happen to find ourselves in one fine-tuned the way it is) is to explain
away the problem of fine-tuning. One can (and many have) equally argue that God did it and state with just as much validity that this is an explanation. It is, but it is a poor one.
Its obviously not fleshed out, but there are numerous prominent scientists pursuing this theory actively.
And most of them continue to subscribe to a theory that not only hasn't generated any testable prediction in over 30 years, if a consistent, complete version of the theory were derived it would necessarily lack all predictive power because of the infinitely many ways to compactify the extra dimensions. The public is generally unaware of how much high energy physicists, theoretical physicists, particle physicists, cosmologists, etc., rely one theory-construction using mathematical derivations and
ad hoc mathematical solutions (and I'm not talking about the use of Noether's theorem and the use of symmetry to formulate theories via conservation entailed by the theorem).
Clearly there is something to it, or rather scientists believe that it eventually might be developed enough to have some explanatory power.
Many scientists who are supporters don't think the multiverse theories will ever be testable. Some are so thoroughly caught up in the idea that modern fundamental physics is essentially mathematically derived and often built upon more fundamental theories that were never and currently cannot be tested that they subscribe to the ideology that mathematics is reality. The best example of this view may be found in the writings of Tegmark, whose popular book
Our Mathematical Universe takes Wigner's "unreasonable effectiveness of mathematics" to the extreme by positing that reality is mathematics. A similar view is widespread particularly among promoters of multiverse cosmologies and string theories, but is also an unfortunate side-effect of the nature of fundamental physics and the divide between the formalisms and the physics present in QM and all extensions of it (e.g., QFT, QED, quantum loop gravity, particle physics, etc.).
