Three weeks ago, Kepler astronomers found eight planets that are in their star's "goldilocks zone" - not too hot, not too cold, but just right for liquid water.
Now, there is a lot more going on than just having an orbit that fits into circumstellar habitable zone. Those planets will need a certain range in mass, a certain balanced chemical composition, a presence of liquid water, but not too much or too little, in order for our kind of life to emerge and thrive.
It actually gets pretty complicated pretty quickly, and so I would suggest that the wrong fairy tale is being referenced, that rather than Goldilocks and the Three Bears, we would be better off with Cinderella.
Cinderella is a beautiful young girl being abusively raised by her wicked stepmother and tortured by her wicked stepsisters. Her fairy godmother helps her go to a ball where she meets a handsome prince, loses a slipper, and runs away. The handsome prince scours the kingdom looking for the owner of the lost shoe, finds Cinderella, the shoe fits, and they live happily ever after.
So, the analogy of Cinderella is only going to go so far. But let's try it anyway. The Cinderella is the planet. The prince is carbon-based, water-mediated life. The wicked stepmother and stepsisters are the universe at large, which - despite the increasing empirical evidence of possessing extremely fine-tuned physical constants to harbor our kind of life - is quite inimical towards our kind of life.
What with gamma ray bursters, and supernovae, and quasars, and black holes, and colliding neutron stars, the universe, like a playful little kitten, seems determined to kill us in as cute a fashion as it can. And then there is planetary formation, with all the mathematical chaos involved in that. For every cinderella planet, a candidate for life, there has got to be a million wicked stepmothers ready to fuck things up. Like, for example, gas giants forming in unstable orbits that fling planets out into the void, or unstable stars that hiss and spit hard radiation and deadly flares, ready to freeze/dry or pan fry life at the get-go.
And then there are, again, a billion ugly stepsisters for every cinderella, planets that look like Mercury, or Venus, or Mars, and just ain't never gonna give life a chance, and, in fact, may even go out of their way to fuck things up for a cinderella planet. In fact, I insist that the cinderella planet be fucked with, otherwise you don't need the later happy circumstance of a fairy godmother.
And in fact that's kind of the point. If any run-of-the-mill planet can harbor life right out of the gate, it's not all that impressive. Ah, but an abused planet, one that has a tough uphill climb, one that gets a really lucky break, one that our prince finds a shoe match, why that's Earth, and the other eighteen worlds in the universe that are earthlike*.
Consider Earth. It probably started out outside of the goldilocks zone, should have been frozen solid, with too little mass, gets rear-ended by a Mars-sized planetoid, which beefed up prot-earth, and just barely made an appropriately sized moon, with just the right mass, starting out at just the right orbit, with the planet rotating at just the right speed, so that our axis remained stable over billions of years. It didn't have to be that way. Someone took their magic wand and provided just the right amount of good fortune. And then the prince stopped by with his shoe, and here we are.
Am I suggesting the fairy godmother is some intentional power? Nope, just dumb luck. That's how you get lucky planets like ours.
In fact, as earth like planets go, I'd bet ours isn't even the most optimal. We are probably just barely marginal for supporting life.
How Anthropic of the universe!