The last part of the article, however, is still quite intriguing. Nobody would expect any of the 3 components of alpha to change, unless somehow the measurements can be affected by the medium (as the speed of light depends on that).
I think invoking the Anthropic principle only makes sense if we can demonstrate that there are a number of other "places" with varying "conditions". For such a selection bias to occur there needs to be a population to actually select from. For example, the Anthropic principle makes sense regarding the composition of the earth because we know that there are a large number of planets with a distribution of orbits and masses around a distribution of stars. Of course we will be on a planet that supports life as we know it.
To invoke the anthropic principle regarding a constant would imply — to me, at least — that there would need to be a number of universes with different constants. Or different regions of this universe where the constant would vary.
If there truly is only a single universe, and the constant is not changing in time or space, then it would seem we did actually just happen to get lucky.
Edit: of course, at this point we can't say definitely either way about our universe. We don't know if ours is one among many, or if its the solitary universe in existence. We also, clearly, have uncertainty about how constant this constant actually is.
There are a couple challenges to these measurements, though. Sean Carrol presents a theoretical challenge in his blog post "The Fine Structure Constant is Probably Constant"[1]. Chad Orzel has a more observational critique of the results in "Why I’m Skeptical About the Changing Fine-Structure Constant" [2].
To be fair, these critiques are from 2010 and Webb, et al. has published several papers since these critiques were made. I haven't seen updated debate or discussion over Webb, et al's findings. Still, I would think we have some potential evidence that the constant may vary, but I don't think this evidence is near conclusive yet.
[1] http://www.preposterousuniverse.com/blog/2010/10/18/the-fine...
[2] http://scienceblogs.com/principles/2010/09/14/httpksjtracker...
H&H spend a lot of time comparing themselves to the approach of selecting an initial values surface in the early universe and marching it forward; they more or less do the same but flip the direction of the arrow of time and arrive at a superposed state. Re-flipping the arrow of time leads to relic fields like the CMB carrying evidence for the superposition.
Essentially this is just taking time-reversibility of local microscopic physics seriously (great), and absorbing the difference in degrees of freedom in macroscopic physics into a superposition (uh, ok). The problem of setting up a values surface remains pretty much the same. "Fine tuning" is just a way of saying that the system is sensitive to the values it evolves from (or to).
I'm not really convinced that that a present-day spacelike hypersurface is easier to write down than an early-time initial values surface.
ArXiv version: http://arxiv.org/abs/hep-th/0602091
Thanks for the link, though! I'll get studying.
I think this entire discussion is sensitive to exactly what one means by "The Anthropic Principle". If one's definition of the Anthropic Principle in this context simply means that an observed universe will be consistent with a universe that can be observed, then I find it to be trivially true and applicable to a single universe scenario.
I subscribe to a definition of the anthropic principle that invokes selection bias as its core mechanism. I think that, in order to have a selection bias, one needs to actually be selecting from a population. Hence my assertion that you need a multi-verse (with different constants in each universe) or a constant that is variable in space or time [2].
The difference, to me, is this:
If you are selecting from a population the Anthropic Principle can actually help explain why a value is what it is. Under our understanding of planetary bodies, we often invoke the Anthropic Principle to explain why the earth falls in the habitable-zone. Earth falls in the habitable-zone because — we think — life is most likely to arise on a planet in that zone.
However, if you are not selecting from a population, I don't find that the Anthropic Principle explains why a value is what it is. In the scenario where there is only a single value, I think the Anthropic Principle simply demonstrates that that particular value must support life.
Put another way, if all planets we observed were the exact same distance from their star as Earth [1], then we couldn't use the Anthropic Principle to explain why Earth is that particular distance from the sun. We would have to find other astronomical reasons to explain why planets form at that specific distance from a star. In this single-distance scenario the only thing the Anthropic Principle actually does for us is confirm that such a distance supports life.
[1] Well, not distance per se, but placed such that they received the same amount of stellar energy in their orbits.
[2] This final sentence of the introduction of the Anthropic Principle also makes some reference to this saying: "Most often such arguments draw upon some notion of the multiverse for there to be a statistical population of universes to select from and from which selection bias (our observance of only this universe, compatible with life) could occur."
It is "trivially" true in a sense. It's a tautology. But it's still useful for thinking about things. I think it applies just as well to a single universe or a multiverse, because even with a single universe you can at least hypothesize about other ways the single universe could behave.
> However, if you are not selecting from a population, I don't find that the Anthropic Principle explains why a value is what it is. In the scenario where there is only a single value, I think the Anthropic Principle simply demonstrates that that particular value must support life.
It might not answer the extremely broad and ill-defined question "why" to your satisfaction, but I find it fairly satisfying. If things were another way, then I wouldn't be observing the universe because I wouldn't exist. So it's not strange that the universe is this way, given that I exist.
Edit: It's hard to come up with a good analogy because obviously I don't have that "perfect" language at my disposal. But for example, a triangle fundamentally has 3 angles. We can imagine polygons with more angles, but it doesn't make sense to imagine a triangle with any other number of angles. If "the whole universe" were synonymous with "triangle", the notion of "universe with 4 angles" would be absurd. The ideal description would not even allow for that possibility.
If there is only one value, the universe can't "plan" or "choose" a value that is conducive to life, and so pointing to its suitability for life is a teleological argument-- it explains a cause (the value of the constant) in terms of its effect (the eventual existence of life). That's backwards and circular-- causes come before effects.
That is, the anthropic principle doesn't try to "explain" why a constant takes a value. It just notes that the conditional property of us observing that value (given that we exist) is 1, regardless of what the unconditional property might be (or even whether it's variable to begin with).
The Anthropic Principle is usually invoked to explain why two very large dimensionless numbers, i.e. the inverse gravitational "fine structure constant" (which is assumed to be constant), and the age of the universe measured in atomic units (which increases with time), are both very close to 10^40. It is suggested that, for intelligent life to evolve and measure them, the two numbers must be roughly equal, and other dimensionless numbers, such as the electromagnetic fine structure constant, must similarly have values within a narrow range. And this in turn has led some people to believe it's the deliberate action of a creator, or that there are numerous other universes whose constants have different values, and almost all are devoid of life.
Fine-tuned Universe: https://en.wikipedia.org/wiki/Fine-tuned_Universe
However, if we apply this Anthropic Principle to planetary orbits, we could conclude that planetary orbits are roughly circular because, if they were (for example) very long rectangles (or some other random shape), we wouldn't be around to observe their shape.
Of course, no one believes that. It is accepted that Celestial Mechanics, based on Newton's Law of Gravity, (which can be derived from the more accurate General Theory of Relativity), adequately explains why planetary orbits are roughly circular.
An alternative explanation is that we simply haven't worked out all the physical laws. For example, the force of gravity could become weaker as the universe gets older or less dense (or, expressed in different units, gravity remains constant but elementary particles get lighter). Dirac, and later a few others including myself, modified Einstein's equations in an attempt to explain this coincidence.
Dirac large numbers hypothesis: https://en.wikipedia.org/wiki/Dirac_large_numbers_hypothesis
Another argument against fine tuning is the Inverse gambler's fallacy: https://en.wikipedia.org/wiki/Inverse_gambler's_fallacy
In other words, things are the way they are because we wouldn't be able to fall in love, dance to the music and enjoy life, if things were otherwise.
Thinking too much about why, distracts from the now. Mystery is what makes life worth living. And hiding ourselves from our self is what makes discovery possible.
If reality is a computer simulation, then proving that is a bit redundant in my opinion.
However, I think it can be proven but once it is, what will there be to know?
If reality is a computer simulation I can think of a multitude of other questions about reality:
- Can we communicate "outside" of the simulation?
- Is the simulation a product of intelligence that is intentionally running the simulation? Or is it a mere by-product of a higher-order universe?
- By studying the simulation in great enough detail, is there anything we can learn about the "outside" universe?
- Is the "outside" simulation a turing machine? Can it compute a higher class of computational problems?
- Are the simulations infinite? Is the "outside" also a simulation? Is it simulations all the way down — or all the way up? Is there a "real" reality?
- If its simulations all the way down, how did the first simulation get started?
- If there is a "real" reality we get to start all of science over at square one studying this new reality.
This is a rough initial list, but I'm sure there's an endless number of questions to be asked and answered about reality even if we prove its a simulation.
Consider the broader philosophical implications of what I wrote. And proving it was a simulation would explain all those questions you proposed.
I have asked some of the smartest people I know about this topic, and no one seems to know.
It would be awesome if someone reading this thread knew something unique about it and emailed me. That's my only motivation.
I may well have missed the point, though if I have done so because you purposely wrote obtusely then I have no real interest in attempting to decode your writing. I wish you luck in your ventures, and hope someone with more time and ability than I discovers your writings and sends you the e-mail you desire.