One of the most startling scientific discoveries of recent decades is that physics appears to be attuned to life. This means that for life to be possible, certain numbers in physics had to fall within a certain, very narrow range.
One of the examples of fine-tuning that has most baffled physicists is the power of dark energy, the force driving the accelerating expansion of the universe.
If that force had been just a little bit stronger, the matter would not have been able to clump together. No two particles would ever have combined, meaning there would be no stars, planets, or any form of structural complexity, and therefore no life.
If that force had been significantly weaker, it would not have counteracted gravity. This means that within the first fraction of a second, the universe would have collapsed back in on itself – again meaning there would be no stars, planets or life. To make the possibility of life possible, the power of dark energy, like Goldilocks’ porridge, had to be “just right.”
This is just one example, and there are many more.
The most popular explanation for the sophistication of physics is that we live in one universe in a multiverse. If enough people buy lottery tickets, it becomes likely that someone will have the right numbers to win.
Likewise, if there are enough universes, with different numbers in their physics, it becomes likely that a given universe will have the right numbers for life.
For a long time this seemed to me the most plausible explanation for sophistication. However, experts in probability mathematics have identified the inference of refining a multiverse as an example of fallacious reasoning – something I explore in my new book, Why? The purpose of the universe. Specifically, the accusation is that multiverse theorists are guilty of what is called the inverse gambler’s fallacy.
Suppose Betty is the only person playing at her local bingo hall one night, and by some incredible stroke of luck, all her numbers come up in the first minute.
Betty thinks to herself, “Wow, there must be a lot of people playing bingo in other bingo halls tonight!” Her reasoning is: if there are many people playing throughout the country, then it is not that unlikely that someone will have all their numbers announced in the first minute.
But this is an example of the reverse gambler’s fallacy. No matter how many people do or don’t play in other bingo halls around the country, according to probability theory, it couldn’t be more likely that Betty herself would be that lucky.
It’s just like rolling dice. If we get multiple sixes in a row, we incorrectly assume that we are less likely to get sixes in the next few rolls. And if we don’t get sixes for a while, we wrongly assume that there have been a lot of sixes in the past. But in reality, each roll has an exact and equal one in six chance of getting a specific number.
Multiverse theorists commit the same fallacy. They think, “Wow, how unlikely that our universe has the right numbers for life; there must be many other universes with the wrong numbers!”
But this is like Betty thinking she can explain her happiness in terms of other people playing bingo. When this particular universe was created, like a dice roll, it still had a specific, low chance of getting the numbers right.
At this point, multiverse theorists advance the “anthropic principle” – that because we exist, we could not have observed a universe incompatible with life. But that does not mean that such other universes do not exist.
Suppose there is a deranged sniper in the back of the bingo hall, waiting to shoot Betty as soon as a number appears that is not on her bingo card. Now the situation is analogous to the sophistication in the real world: Betty could not have observed anything other than the right numbers for winning, just as we could not have observed a universe with the wrong numbers for life.
Yet Betty would be wrong to conclude that many people play bingo. Likewise, multiverse theorists are wrong when they infer the sophistication of many universes.
What about the multiverse?
However, is there no scientific evidence for a multiverse? Yes and no. In my book I explore the connections between the upside down gambler fallacy and the scientific arguments for the multiverse, something that surprisingly hasn’t been done before.
The scientific inflation theory – the idea that the early universe was greatly inflated in size – supports the multiverse. If inflation can happen once, it will likely happen in different parts of space, creating self-contained universes.
While this may give us preliminary evidence for some kind of multiverse, there is no evidence that the different universes have different numbers in their local physics.
There is a deeper reason why the multiverse explanation fails. Probabilistic reasoning is governed by a principle known as the total evidence requirement, which requires us to work with the most specific evidence we have available.
In terms of fine-tuning, the most specific evidence that people who believe in the multiverse is not just that a universe is fine-tuned, but that this universe is fine-tuned.
If we believe that the constants of our universe are formed by probabilistic processes – as multiverse explanations suggest – then it is incredibly unlikely that this particular universe, unlike another among the millions, would be sophisticated. Once we formulate the evidence correctly, theory cannot take it into account.
The conventional scientific wisdom is that these numbers have remained unchanged since the Big Bang. If this is true, we are faced with a choice. Or it’s an incredible fluke that our universe just happened to have the right numbers.
Or the numbers are the way they are because nature is somehow directed or directed to develop complexity and life by an invisible, built-in principle. In my opinion, the first option is too unlikely to take seriously. My book presents a theory of the second option – cosmic purpose – and discusses its implications for human meaning and purpose.
This is not how we expected the science to turn out. It’s a bit like the 16th century, when we first got evidence that we weren’t at the center of the universe. Many found it difficult to accept that the picture of reality they had become accustomed to no longer explained the data.
I believe we are in the same situation now with the refinement. One day we may be surprised that we ignored for so long what was in plain sight: that the universe favors the existence of life.
Philip Goff, Associate Professor of Philosophy, Durham University
This article is republished from The conversation under a Creative Commons license. Read the original article.
