The Universe is the way it is because things happened the way they did. That doesn't sound particularly mystical to me.
Yet that is the essence of the anthropic principle. It's more usually stated in a manner that causes all kinds of horrid confusion :
"In astrophysics and cosmology, the anthropic principle (from Greek anthropos, meaning "human") is the philosophical consideration that observations of the physical Universe must be compatible with the conscious and sapient life that observes it." - Wikipedia.
Different people have radically different interpretations of what this means. As you'll have already gathered, I fall firmly into the camp which says, "this is trivial, but sometimes useful". In this viewpoint, there is no "reason" that the Universe has physical properties compatible with life. It just does, and so we're here observing it. If things had been any different, we would not be here. Possibly some other lifeform would be around instead, or possibly not, it doesn't really matter.
The reason the anthropic principle is sometimes useful is best explained using maths - very simple maths, don't worry. Suppose I tell you to work out what x is if 5x = 10. Well, that's easy, x = 2. You solved that equation because there was just one unknown variable.
This also works for what seem like more complicated equations :
5x + sin(p) - cos(q) + (r*r*r) + (z*z*z) = 10
If I tell you that p =90 and q =0 and r =176 and z = -176 , it's now simple to work out x (it's two again). This time there were lots of other quantities involved, but since you knew what they all were it was easy to find the unknown variable x.
Anthropic reasoning is a lot like this. It says that since we know life exists, the properties of the Universe have to be compatible with that. So if we know enough about the properties of the Universe, we can work out values we don't know by assuming that they have to be compatible with the existence of life. In many ways, this is incredibly trivial : the Sun didn't explode yesterday, so stars can't be prone to exploding. We didn't get hit by a giant asteroid, so giant asteroids can't be common. And I didn't get eaten by a bear, so bears are rare in Prague.
Let's assume for a moment that that story is exactly true. It scarcely matters that Hoyle was partly made of carbon; it doesn't matter that carbon exists inside Hoyle or inside a wombat, the important point is that carbon exists at all. Moreover, he could equally have done this for another element less important for life. Or, as is very eloquently expressed in The Science of Discworld IV :
"The Anthropic Principle only seems different from the Sulphuric Principle (a universe containing sulphur has to be suitable for making sulphur) because it's about us rather than a lump of yellow rock. But the Copernican Principle cautions us not to imagine that there's anything special about us, and in this case, there isn't. We are just one piece of evidence. An equally convincing case can be made that the Universe is uniquely fine tuned to make sulphur."
Even if you do think we humans are special, the point is clear. We could use anything else as the basis for an anthropic-like principle : monkeys, turkeys, bananas, Justin Beiber, rocks, bum fluff, Sarah Michelle Gellar, candy floss, clouds, lithium, chocolate, volcanoes, sand... whatever you like.
|I already promised not to show Justin Beiber and if you really want pictures of bum fluff then you've come to the wrong place.|
I'll die before I believe in the Beiber Principle, could easily be persuaded in the Gellar Principle, and won't ever stop believing that the purpose of the Universe is chocolate. And I'll actively go around trying to convince people of the Gellar-Chocolate principle. Mmm. Sorry, what was I saying ?
That we are sentient, or even alive, is hardly relevant for anthropic reasoning. The essence of it is that the Universe has to have the correct conditions to contain the things we observe within it - that it happens to include life is just the way it is. That we can sometimes work out other facts about reality from the existence of life doesn't mean that life is special any more than it means sulphur is special.
Why does this cause difficulties ?
The alternative, more extreme view is the so-called "strong" anthropic principle - bluntly stated, the idea that the Universe isn't just suitable for life, but designed for it - it has a purpose, as I alluded to with the chocolate example. This rests on the notion that the properties of the Universe have to be almost exactly what they are, otherwise life would be impossible.
Of course, we could invoke the Strong Sulphuric Principle to see how absurd this potentially is : a Universe containing sulphur doesn't necessarily have to have been designed to contain sulphur, any more than a house containing termites was designed to contain termites. Yes, the house was designed, but assuming some particular random feature of it was the purpose of the house is a very silly mistake.
Or, as in SODIV again :
"Why us ? The Strong Anthropic Principle just assumes it's obvious that we are the purpose of the whole thing. Sulphur ? Don't be silly."
An even better example might be a pile of sand that happens to have a stick on it. The pile of sand wasn't "designed" at all, let alone designed for the stick. The mere fact that things exist doesn't tell you they were designed. It doesn't necessarily tell you that they weren't designed either; the one implies nothing about the other.
But what about fine tuning ? Clearly a pile of sand is not at all fine-tuned, or optimised, to contain a stick. A house is fairly suitable for termites, but it's not ideal unless the entire house is made of wood. In contrast, the argument for the strong anthropic principle for the Universe is that the properties for life are so incredibly specific that it's like balancing a pea on a knife edge - move it even the smallest amount and it will fall. The Universe, it says, is not just suitable but optimal for producing life. And that's much more interesting.
Indeed, one of the most profound discoveries from astronomy is the sheer size of the Universe. We know of only one tiny, pathetic scrap of rock where life like ours can exist. We're special because we're rare, but we're also totally unimportant for exactly the same reason. We matter to each other; the Universe doesn't give a damn.
The problem with the fine-tuning argument, as SODIV point out, is that the Universe is bloody complicated - as are the conditions for life. Change one parameter and you can compensate by changing the others. SODIV present the very nice analogy of a car :
"If you take a car, and change any single aspect even a little bit, the odds are that the car will no longer work. Change the size of the nuts just a little, and they don't fit the bolts and the car falls apart. Change the fuel just a little, and the engine doesn't fire and the car doesn't start. But this does not mean that only one size of nut or bolt is possible in a working car, or only one type of fuel. It tells us that when you change one feature, it has knock-on effects on the others, and those must also change."
Conditions for life aren't balanced on a knife-edge at all : actually, there's a huge plateau containing different combinations of parameters that would give a Universe eminently suitable for life. For example, if the Sun was a little cooler, Earth would be frozen - unless it was also a little closer to the Sun. And smaller, cooler stars live longer than large hot ones, so this might even be better for life in the long run. Similar argument can be made about the particular values of the fundamental constants. So there's not really much indication that ours is the Universe most suitable for life.
Take the carbon example. The energy level did turn out to be close to the predicted value, but you could actually shift that value by around 4% and still get about as much carbon produced as we see. A 4% error isn't precision engineering, it's a wonky stool. In fact you could actually get even more carbon if the energy level was a bit lower.
And then, just for good measure, there's evidence that Hoyle never even used anthropic reasoning and the whole story is a later invention. As I said, the important thing was only that carbon existed, not that Hoyle existed. He could have used an anthropic argument, but a "carbonthropic" principle would have been every bit as valid.
For even more examples of how fine-tuning is a myth, have a look at the Monkey God web program that lets you generate Universes and see how suitable they are for life. And have a read of the author's website too. And of course SODIV's chapter 22 is masterful, even if their discussion on atheism was just plain wrong.
The Earth and the Universe it resides in aren't some wonderful eden. The natural world is, by the standards of human morality, manifestly cruel and unpleasant. Natural selection is a ruthlessly competitive process : you win or you die, or more accurately, you win and you die. Supervolcanoes and asteroid impacts are periodically devastating for the ecosystem - countless species have gone extinct because they were unable to adapt. Life survives in spite of its environment as much as because of it. Arguments that the Universe is uniquely fine-tuned for sentient life don't have much force in the face of tsunamis, earthquakes and hurricanes.
|Yes, this is obviously an example of how suitable the Earth is for sentient life.|
The Universe has properties which are sufficient for life to exist, but that's all we can say for certain. There's little to suggest the Universe is the ideal one for life to survive in, let alone that it was designed for a species inhabiting far, far less than 0.00000000001% of its volume. Virtually all of the Universe is completely unaware of our existence and most of it is an environment that would kill us in seconds. That's a pretty odd bespoke Universe if it's supposed to exist for our benefit, if you ask me.
Used to infer properties of the Universe based on other values, anthropic reasoning is perfectly sound. I would even say it's a very basic scientific idea : if I know some things, I can work out others. But using it to infer a design is ridiculous - of course we live in a Solar System where the planets are in stable orbits, of course we live on a planet with liquid water. The other planets in our Solar System are positively hellish for life as we know it : if there was one just star in all the Universe and the Earth its only planet, then there might be a good reason to suppose that the Universe was designed. But in reality the overwhelming majority of the volume of the Universe is dark, cold and incredibly lonely. That we exist somewhere which is light, warm, and not overtly hostile 100% of the time isn't coincidence, or spooky, it's necessary.
Or to put it another way, saying, "isn't it remarkable how perfect conditions for life are here ?" is as silly as saying, "isn't it remarkable that we live on a rock that's suitable for us to live on, instead of out in that immense cold void where we'd be dead in seconds ?".
The fact that an oasis (at least one) exists where we can survive, given the immensity of the Universe and the huge range of environments, is not in the least bit surprising. The Universe is the way it is because things happened they way they did. Being surprised at this is equivalent to being surprised at the existence of rocks.
None of this makes the Universe the slightest bit less wonderful. Whether you think the Universe is magnificent or oppressive, cruel or beautiful, sacred or profane, is entirely up to you.