Science's Alternative to an Intelligent Creator: the Multiverse Theory
discovermagazine.com
discovermagazine.com
1.) "Life as we know it" is an extremely important phrase. Ask a biologist what life is, and she will probably say something about cells and DNA. It is possible for other self-replicating combinations of molecules to exist, but not on Earth, because the Cell/DNA model has become so effective at wiping the competition out. It's actually really hard to come to a solid definition of what "life" is, but if you make it sufficiently broad, I suspect you could find life even in some universes where the fundamental constants differ significantly from ours.
2.) We have no idea what determines the fundamental constants. You cannot talk about the "odds" of having a universe like ours until you know the probability distributions for each of the fundamental constants. Look at the H2O on Earth, and you will find that a significant portion of it occurs at 0C and 100C. Of course that is not a coincidence - water often exists at those temperatures because energy is spent on converting state, not on altering temperature. It's an equilibrium point. So likewise, it's POSSIBLE that the fundamental constants (of multiple universes, if they exist) interact in ways that cause them to arrive at equilibrium points. One really fascinating theory promoting this idea (and any theory is as good as the next, since we have very little empirical evidence available to us) is Lee Smolin's argument that the singularities within blackholes are themselves universe phases. Thus, a kind of "natural selection" of black holes occurs, which leads to more and more universes with fundamental constants ideal for producing black holes (and thus close to the constants necessary for life).
3.) The anthropic principle is just way too convenient, and I fear it de-motivates scientists from looking deeper into issues that really need explaining. Roger Penrose argues that there is a surprising lack of parsimony on behalf of whatever forces (spiritual or natural) brought about our universe. While our universe appears to have inflated from an initial region with a phase-space-volume of 10^(10^123), it would have been more than sufficient to create a life-supporting universe (several! in fact) from a region with only a phase-space-volume of 10^(10^117). Additionally, Penrose points out that the odds of creating an exact duplicate of our solar system from the random coming together of gas and radiation (no Darwinian evolution necessary!) is only 1 in 10^(10^60). (Penrose calls it "utter chicken feed" compared to the odds of the Big Bang producing ANY universe of our size). So even when you invoke the anthropic principle, the question still remains - why is our (life-supporting) universe so large and so old, when we could have done with so much less?
This I must take issue with. The anthropic principle is what drove the Renaissance. It's what motivated people like Sir Isaac Newton to better understand the universe, they believed that this was the way to get closer to God. The anthropic principle is responsible for the single biggest leap in science in the history of mankind. Saying "God created it" doesn't excuse anyone from anything; you still need to work on it, in fact the good Christian has no excuse not to.
The anthropic principle is dual to Creationism. The Creationist says, "It is because God made it so." The scientist says, "It is because it necessarily must be so." Neither philosophy, by itself, leads to deeper understanding.
This is wrong, with slightly more gravity smaller stars would burn hotter but there is a wide range of stars that can last for 5 billion years. Now if was 100 times as strong they might have a point but there is about an order of magnitude to play around with.
There is some support for Jupitor producing a little fusion with it's current mass. If you increase gravity it becomes smaller until it's heat balances out the force of gravity which increases the amount of fusion taking place.
PS: Less massive stars have a higher surface area to volume ratio. This reduces their temerature which reduces their fuel usage. But once they run out of fuel the same type of interesting things are going to happen.
Unfortunately, without evidence, it's an argument of faith, like any other.
I don't see how belief in "the multiverse" is any different than belief in a god or the simulation hypothesis. They all have zero evidence and can't be tested. The obvious question in all three is: what was there before? So they all have the same problems.
We might also demonstrate that we were in a simulation if we found an exploit to take over the simulator's webcam (assuming the simulator didn't patch and revert). Universal buffer overflow!
The laws of physics are governed by equations which output only a probability distribution P(x) for various quantities (positions of particles, the values of certain fundamental constants).
(Note: I really don't understand any of this stuff well, so if someone (Dani?) with better knowledge can correct me or clarify, I'd love to see it.)
In a single-universe theory (SUT), one postulates that a particular x is selected, at random, relative to P(x) dx. In this theory, it is highly unlikely that the universe can support life (or at least life like us). In a multiverse theory (MUT), one postulates that all x are selected in parallel. In this case, our particular x will be chosen; the fact that we live in a good universe is not luck, merely natural selection. So the probability we exist is close to 1.
Both these theories are more or less equally "simple" (think Kolmogorov complexity), so let us assume they each "occur" with the same or similar "probability" (i.e., p(SUT)=p(MUT)=1/2). Then we use Bayes rule:
p(SUT | we exist) = p(we exist | SUT) p(SUT) / p(we exist) = (really freakin low) (1/2) / (1/2+really freakin low) = (unlikely)
p(MUT | we exist) = p(we exist | MUT) p(MUT) / p(we exist) = (almost 1) (1/2) / (1/2 + really freakin low) = (highly likely)
So multiverse theory is more "probable" than single universe theory. This remains true even if you wildly alter the complexity of competing theories, e.g. p(SUT)/p(MUT) = 1e6.
It's true, we can never falsify SUT or MUT relative to each other. But we can make educated guesses as to which one is more "probable". And yes, this is pretty sketchy, hence my use of scare quotes everywhere. But it's the best we can do right now.
Note: I computed p(we exist) = p(MUT)p(we exist | MUT) + p(SUT)p(we exist) = (1/2) 1 + (1/2)(really freakin low).
[edit: just curious why I'm being downmodded. Not begging for upmods, I'm honestly curious. Did I make a mistake here?]
I did a physics degree. I studied atomic physics and quantum mechanics. We briefly brushed on the multi/single universe, but largely that was not examined in too much detail in the physics cursus. People who were doing Physics & Philosophy, however, got plenty of detail in their course. My point being: this is philosophy, not science.
[edit: my turn to wonder why I am being downmodded, lol]
The question is 'absent plausible experiments, how do we choose between single and multiple universes?' And that is done using occams razor; the 'simpler' or 'more probable' theory is chosen, for a somewhat (but not completely) arbitrary definition of 'simpler'.
Occams razor is a philosophical point, as is (to some extent) your definition of 'simpler'. I thought I was careful to highlight those points.
I was merely trying to explain the reasoning multiverse theory, but in a less vague manner than the article did (I trust most of HN to know Bayes rule).
Incidentally, this thread is bringing out behavior which is weird for HN. Someone downmodded your comment, also for reasons which are completely inscrutable to me.
For the record, I haven't read the article in question closely enough to know if what's being proposed can even be falsified in principle.
It seems more likely to me that "universe" here is being defined as "what we can observe", in which case these multiverses are simply the unobservable part of our universe.
The Many-Worlds hypothesis also implies separate "realities" ("universes"?) diverge with every quantum measurement.
The word is used for convenience.
I'll consider any theory seriously that is:
1. Very simple
2. Very stable
why?
1. Single instable thing exists that tends to combine with other items to form a somewhat stable object
2. The results combine with other more complex things in the same manner to create something else
It's like a recursion. Something simple gets executed over and over again, each time gaining in parameters and complexity.
I like the multiverse concept. Its cool. Maybe a creator created this ;)
Let us say that a hyper-advanced civilization has the ability, through simulations or otherwise, of calculating the odds of life arising in a universe with given initial conditions and fundamental constants (to some rough accuracy). They can test billions of possible initial states, including our own, and use that to see whether we lie in a very probable location in phase space or an improbable one. If the location is probable, it strongly supports the multiverse theory.
If the location is improbable, the theory is likely false. For example, if the average probability of life arising in a given universe in some chunk of phase space that includes ours is 40%, and ours is in a subsection of that phase space with a 30% probability, the multiverse theory is not falsified. If ours is in a subsection of that phase space with a 0.000001% probability (far lower than average), it suggests that multiverse is unlikely, because our existence seems to be in violation of pure chance.
The same method can be used to falsify evolution. Test billions of simulations of the Earth's development of life, and see where our species falls statistically. If we're in a probable area of the phase space (phase space of possible sentient creatures to evolve), our understanding of evolution is likely correct, and if we're in a very improbable area (many many standard deviations away from the most likely), our understanding must be flawed somewhere.
Statistical analysis of probabilities is a method of analyzing the odds of a theory's validity. If a theory requires that reality be extremely improbable, that theory is highly unlikely. And when there's absolutely nothing else you can do, its the only option other than blind faith.
I'll repeat this again:
If a theory requires that reality be extremely improbable, that theory is highly unlikely.
The entire point of the Anthropic Principle is to attempt to answer this question by stating that if reality was not improbable as such, we wouldn't exist to ask that question.
Do you object to this concept? How is this concept a violation of the scientific method?
http://en.wikipedia.org/wiki/Scientific_method
In it, you will find the "essential elements" of the scientific method:
* Characterizations (observations, definitions, and measurements of the subject of inquiry)
* Hypotheses (theoretical, hypothetical explanations of observations and measurements of the subject)
* Predictions (reasoning including logical deduction from the hypothesis or theory)
* Experiments (tests of all of the above)
Please note that the anthropic principle is not a scientific theory, it is a wild guess at why things might be what they are.
If a theory requires that reality be extremely improbable, that theory is highly unlikely.
This is a very wild conjecture with no substantiating evidence. It is wholly equal to blind faith, and in no way superior to it.
It is wholly equal to blind faith, and in no way superior to it.
So, by your logic, the anthropic principle is wholly equal to blind faith? Sure, its not strictly science, and more of a logical argument than a scientific experiment (much like my original post), but really? Equal to blind faith?
If you are that deluded, I'm not even going to bother arguing this. This is pointless. Go get yourself a source a bit better than Wikipedia and educate yourself.
In terms of intellectual "worth thinking about"-ness, the anthropic principle may be more worthwhile than blind faith, but in terms of science, it is equally worthless.
You need to revise your understanding of how science works, or else you'll only continue to blunder around.
the universe has almost countless variables that can result in near-infinite states, but there is a 100% chance that one state must emerge (i.e. a 100% chance that reality exists), and it isn't clear if the alternative scenarios they describe (particles of different masses, stronger gravitational impact on stellar mass) are more probable than our own. the scientists see our state as optimal because we live in it, but why couldn't our state be suboptimal? maybe there was a potential state (never realized) that resulted in us all being omnipotent. there seems to be a bias from the researchers regarding our own state, but they haven't demonstrated that its any more or less likely than any other outcome