Today I want to talk about the claim that our universe is made specifically for humans or is tuned to life. According to this notion, it is extremely unlikely that our universe happens to be the way it happens to be, and the fact that we exist nonetheless needs some explanation. This argument is popular with some religious people who claim that our universe needs a creator, and the same argument is used by physicists to pass off unscientific ideas like the multiverse or naturalness as science. In this video I will explain what is wrong with this argument and why the observation that the universe is one way and no other is no evidence for or against God or the multiverse.
Ok, here’s how to get to the heart of the argument. The currently known laws of nature contain constants. Some of these constants are, for example, the fine structure constant, which determines the strength of the electromagnetic force, Planck’s constant, Newton’s constant, the cosmological constant, the mass of the Higgs boson, etc.
Now you can ask what a universe would look like if one or more of these constants were a little bit different. It turns out that for some changes in these constants, processes essential to life as we know them cannot take place and we cannot exist. For example, if the cosmological constant were too large, galaxies would never form. If the electromagnetic force were too strong, nuclear fusion would not be able to make stars shine. And so on. There’s a long list of calculations of this type, but they’re not the relevant part of the argument, so I don’t want to go through the entire list.
The relevant part of the argument is as follows: It is extremely unlikely that these constants would have the exact values that enable our existence. Hence, the universe as we observe it needs an explanation. And then that declaration can be God or the multiverse or whatever your favorite idea is. Particle physicists use the same type of argument when asking about the next larger particle collider. In this case, they claim an explanation is needed as to why the mass of the Higgs boson happens to be what it is. This is called a “naturalness” argument. I explained this in a previous video.
What’s wrong with the argument? What is wrong is to claim that the values of the natural constants we observe are improbable. There is no way of ever quantifying this probability, as we will never measure a natural constant that has a different value from what it has. If you want to quantify a probability, you need to collect a sample of data. For example, you could do this by throwing the dice. Throw them enough times and you will get an empirically based probability distribution.
However, we do not have an empirically based probability distribution for the constants of nature. And why is that. It’s because … they’re constant. To say that the only value we have ever observed is “unlikely” is a scientifically meaningless statement. We have no data and will never have data that will allow us to quantify the likelihood of something we cannot observe. There is nothing that is quantifiably improbable, so there is nothing that needs explanation.
If you look at the published literature on the alleged “fine-tuning” of the constants of nature, the error is always the same. They only postulate a certain probability distribution. It is this postulate that leads to their conclusion. This is one of the most well-known errors of logic known as the “questioning” or “circular reasoning”. You assume what you have to show. And instead of showing that a value is unlikely, they choose a certain probability distribution that makes it unlikely. You could also choose a probability distribution that makes the observed values * probable, only that it doesn’t produce the desired result.
By the way, even if you could measure a probability distribution for nature’s constants that you can’t, the idea that our particular combination of constants is necessary for life would still be wrong. In the scientific literature there are several examples of laws of nature with constants that have nothing to do with our own and, for all we can say, allow for a chemistry complex enough for life. Please check the information below the video for references.
Let me make it clear, however, that fine-tuning arguments aren’t always unscientific. The most famous example of a good fine-tuning argument is a pen that is balanced on its tip. If you saw this you would be surprised. Because this is very unlikely. They would be looking for an explanation, some hidden mechanism. That sounds very similar to the argument for fine-tuning the natural constants, but the balanced pen is a completely different situation. The claim that the balanced pen is unlikely is based on data. You are surprised because you usually don’t come across pens that are balanced at their tip. You have experience, which means you have statistics. But it’s completely different when you talk about changing constants that cannot be changed by any physical process. Not only do we have no experience with it, we never have any experience.
I should add there are Theories where the constants of nature are replaced with parameters that can change with time or place, but that’s a whole different story and has nothing to do with the fine-tuning arguments. It’s an interesting idea, however. Maybe I should talk about it another time? Let me know in the comments.
And for the experts, yes, so far I have been referring specifically to the so-called frequentist interpretation of probability. Alternatively, you can interpret the term “unlikely” using Bayesian probability interpretation. In a Bayesian sense, to say that something you are observing is “unlikely” means that you did not expect it. But with Bayesian interpretation, the whole argument that the universe was made especially for us doesn’t work. That’s because, in this case, it’s easy enough to come up with reasons why your probability score was just wrong and there is nothing to explain.
Example: A year ago, did you expect that we would have spent much of 2020 on the lockdown? Probably not. You probably thought that was unlikely. But no one would argue that you need God to explain why it seemed unlikely.
What does this mean for the existence of God or the multiverse? Both are assumptions that unnecessarily complement our natural theories. In the first case you say, “The constants of nature in our universe are what we have measured and God created them.” In the second case you say, “The constants of nature in our universe are what we have measured , and there are an infinite number of other unobservable universes with other constants of nature. “Neither of the two additions will help improve our natural theories. However, this does not mean that God or the multiverse does not exist. It just means that evidence can’t tell us whether it exists or not. It means that God and the multiverse are not scientific ideas.
If you’d like to learn more about fine-tuning, I’ve explained all of this in detail in my book, Lost in Math.
In summary: was the universe made for us? We have no evidence whatsoever that this is the case.
You can chat about this video here today (Saturday, January 16) at 6 p.m. CET / Eastern Time.