A Fortunate Universe: Life in a Finely Tuned Cosmos

"A Fortunate Universe: Life in a Finely Tuned Cosmos . This is a book written by two cosmologists, Luke Barnes and Geraint Lewis, and published in 2016. A cosmologist is a physicist with expertise in studying the universe on a large scale: planets, stars, the Big Bang . This book lays out the contemporary evidence for what we call cosmological fine-tuning – the idea that at least in our current best theories for life to be possible at all, certain numbers in physics had to fall within a certain narrow range. The example that has baffled physicists the most has to do with the cosmological constant. This is the number that measures the acceleration of the universe. In 1998, we discovered that the universe is not only expanding, it’s also accelerating in its expansion. Physicists postulate a force that’s pushing the universe apart, which we call dark energy, and the number that measures that force is called the cosmological constant. If that force was a little bit stronger, everything would have been pushed apart so quickly that no two particles would have ever met, so we wouldn’t have had stars, planets, any structural complexity, and therefore, no life, presumably. If it had been a little bit weaker, it would have increased gravity, and everything would have collapsed in the first split second. That’s a good analogy. There are some cases in which we’re happy to accept improbable things, and there are some cases in which we’re not. Here’s a good example. Suppose we have a random number generator, and it spits out a number: 5769126. If, after the fact, I say, ‘I think there’s a god who really likes that particular number’, you would say, ‘Oh, come on. That’s totally ad hoc. You just said it after the fact, so no one will take you seriously.’ But if I’ve been leading a religious cult for decades that says there’s a god that loves this particular number and that this random number generator will spit out this number on exactly this date, we wouldn’t say, ‘It’s just a coincidence.’ We would say, ‘It’s very improbable that you’d get all of these elements right.’ The question is, what differentiates these cases? The great thing now is that we don’t have to be so intuitive. We have Bayes’ theorem, which gives us a disciplined way of thinking about these probabilities claims. Without getting into the mathematics, it is about which possibilities are special or interesting independently of them happening to be the outcome. Absolutely. There are two considerations. The first being how improbable an outcome is. In my book, I give the example of Jesus appearing on toast. It’s a little bit improbable, and that’s why we enjoy it, but it’s not that improbable. Because it’s not so improbable, we’re happy to accept it’s just a fun coincidence that you sometimes get a burn mark in toast uncannily shaped like Jesus. Indeed. In these cases, we’re not dealing with something that ludicrously improbable. But when it comes to fine-tuning, the numbers we are talking about are so extraordinary that saying ‘it’s just chance’ is not rationally sustainable. The second consideration is whether the improbability is significant independently of it having happened to occur. Take the example you mentioned of me having been born, instead of my father having married someone else and had a different child. It’s not particularly special that I was born instead of someone else – my ego isn’t that inflated! But now contrast with fine-tuning. It’s true that whichever numbers come up in physics, in some sense, these are going to be improbable; however, what is striking is that, of all the numbers that might have come up, the ones that have come up are in the rare range that allow for something quite special – structural complexity, intelligent life. That’s why it’s different to your example of my dad marrying someone else. These things of great value allow for the possibility of people writing poetry, falling in love, contemplating their own existence, whereas the majority of the possible numbers would create a universe of, say, only hydrogen, with no complexity. What is striking is that not only are the numbers improbable, the numbers that came up are those that allow for these things of value and significance. I think that’s where we feel that it needs some kind of explanation. In terms of the lottery case, there are two issues here. Again, it depends on whether the outcome was significant independently of it happening to be the outcome. If Joe Bloggs wins the lottery, there’s nothing significant there. It is improbable, but someone had to win. However, if the partner of the boss of the lottery wins, then we think something’s going on. That person has a certain significance that’s independent of the fact that they happen to win. What you’re also pointing to is another very common reaction, which is sometimes called the anthropic principle. If the universe hadn’t been fine-tuned for life, then we wouldn’t have been around to think about it, so it is inevitable, given that we’re here, that the universe is going to be fine-tuned. People have often tweeted at me the puddle analogy from Douglas Adams . He imagined a puddle waking up and saying, “Oh my gosh – this hole in the ground is perfectly suited for me.” One of the most vivid ways of responding to that objection is John Leslie’s firing squad analogy, which appears in his book Universes , which we’ll be discussing later. Imagine you are going to be executed. You are terrified. Five expert marksmen get their guns ready. They all fire, and they all miss. They reload, and they fire. Once again, they all miss. They keep missing, time and time again. What are you going to think? Presumably, you are going to think, ‘This needs an explanation. It’s very improbable that these expert marksmen happen to miss every time.’ However, if you buy this anthropic line, then you will think, ‘Actually, if they had hit me, I wouldn’t be here to think about it. It’s inevitable, so it doesn’t need explanation.’ I don’t think anyone would really think that, but if it doesn’t apply in this case, then I don’t think it applies in the fine-tuning case. It is trivially true that if the universe hadn’t been fine-tuned for life or life conducive, we wouldn’t be around; however, I don’t believe this removes the need to explain it. That becomes clearer when we put things in precise Bayesian terms, which you might not want to get into, but it’s hard to see why that affects the probabilistic argument. Although it’s true, it’s hard to see why it affects the argument. Support Five Books Five Books interviews are expensive to produce. If you're enjoying this interview, please support us by donating a small amount . Having said that, some philosophers have tried to make sense of this anthropic objection; I don’t want to imply that it’s just an online objection. Elliott Sober, a wonderful philosopher of biology, engages with these arguments, and he tries to rigorously make that argument work. It is a response that can be made, but I don’t buy it myself. Another interesting thing about this book is that it explores both of the two standard explanations of fine-tuning: God, and the multiverse. The multiverse hypothesis is that there is a huge, perhaps infinite, number of universes, each having different numbers in their physics. In some, the cosmological constant is stronger, and in others, it’s weaker; in some, gravity is stronger, and in others, it’s weaker, and so on. If you have enough variety throughout the universes, then it’s not so improbable that one of them is going to happen to have the right numbers for life. Then, the lottery response starts to be a little bit more credible. If enough people are playing the lottery, then somebody’s going to win. The authors are both cosmologists, as I’ve mentioned. One of them is a Christian and goes for the God explanation, and the other one is a multiverse theorist and goes for that explanation. Most of the book presents the cutting-edge physics on this in a very clear and accessible way, and the final chapter is a dialogue between the two of them. It’s fun. They’re down to earth, and they’re very clear. They’re also philosophically clued up, which isn’t always the case with physicists. It’s a very interesting discussion of these two rival hypotheses. This book is a bit different from the others I’ve chosen, in that it isn’t going for some alternative to God, between God and atheism. I’ve put it on the list because it is a very good presentation of the cutting-edge evidence for fine-tuning, which is motivating so many of these philosophers and myself to take cosmic purpose seriously."