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Our future, our universe, and other weighty topics


Thursday, May 17, 2018

Three Fallacies in This Week's “Multiverse News” Story

May 14, 2018 was another day showing that a good deal of what you read in the science news has little relation to fact. Besides some misleading neuroscience headlines I'll discuss in another post, there were news stories about some cosmological research. Fox News covered it with a headline of “Scientists believe alien life may exist in other universes after discovering a mysterious 'force.'” The “force” referred to is the cosmological constant, which was discovered to exist more than 25 years ago. So the implication of the headline (that some new force was recently discovered) is bunk. The Live Science site reported the same research as “Aliens May Well Exist in a Parallel Universe, New Studies Find.” The Daily Mail reported the same research with the headline, "Our universe may be one of many with life." 

The studies in question were actually “no real news” type of affairs. They considered what is called the cosmological constant or dark energy, which is basically the same as the vacuum energy density or the energy density of empty space. The studies found that in some other universe such a thing might be up to 300 times greater without ruling out life in such a universe. This is “no real news” in the sense that this was already known.

What we have in our universe is a vacuum energy density or cosmological constant that seems not quite zero but very close to zero. This means that the vacuum of space is very close to being devoid of energy. So it's hardly a surprise that you could multiply by a few hundred times this “very close to nothing” energy density of the vacuum, without affecting the universe's habitability.

But our science news media has distorted such studies, drawing unwarranted conclusions from them. For example, the Live Science story claimed this: “According to a new pair of studies in the journal Monthly Notices of the Royal Astronomical Society, there’s a decent chance that life-fostering planets could exist in a parallel universe.” I will now explain three fallacies involved in such claims, which certainly do not follow from the studies in question.

Fallacy 1: The Fallacy of Mistaking “Could Be Much Different Without Ruining Things” with “Being Likely to Be Life-Compatible”

Let us consider some particular parameter in a universe: for example, the strength of the gravitational constant. Imagine you show that such a parameter could vary by 100 times without ruining the chances of life in our universe. Would such a parameter be likely to be compatible with life's existence in a random universe? Not at all. Whether a particular parameter could be much different without ruining a universe's habitability (call this Question A) is a much different question than whether such a parameter would be likely to have a value not ruining the chances of life in a random universe (call this Question B).

How can we calculate this Question B? You would have to numerically compare two ranges of values: (1) a range of values (call it Range A) that the parameter could have without preventing life in our universe; (2) a much larger set of values (call it Range B) that the parameter might possibly have had.

Let's try this in the case of the gravitational constant. We know that the universe has four fundamental forces (the gravitational force, the weak nuclear force, the electromagnetic force, and the strong nuclear force). We also know that the ratio between the strongest of the forces (the strong nuclear force) and the weakest of these forces (the gravitational force) is about 10 to the fortieth power or 1040. So in estimating the set of values that any of these four forces might have had in a possible universe, a reasonable approach would be to assume that any of them might have varied by a factor of 1040. So for the gravitational constant it would seem that Range B should be something like the range of values between a value 1040 times smaller than the current value of the gravitational constant and a value 1040 times larger than the current value of the gravitational constant. But in this case Range A would only be a microscopic fraction of this Range B, because there are reasons why life could not exist in our universe if the gravitational constant was much more than about 100 times larger or smaller.

The ratio between this Range A and Range B is actually about 1 in 10 to the thirty-seventh power. So in the case of the gravitational constant two things are true: (1) the current value of the constant could be no more than about a hundred times larger or smaller without ruining the universe's chance of life; (2) the chance of such luck in a random universe seems to be less than 1 in 10,000,000,000,000,000,000,000,000,000.

I can give an analogy. Imagine there's an office door that requires people entering to type their 10-digit social security number. Imagine there are 100 employees in the office. In this case there are 100 random numbers you can type that would get you inside the office. But there's still only a tiny chance of success with a random number. So you should not at all make the mistake of thinking, “There's a good chance of getting in; there are a hundred numbers that will get you in.” The chance of getting in with a random number is actually less than 1 in 100 million. And similarly, the chance of a random universe having a life-compatible gravitational constant is much less than 1 in a billion, even though there are multiple random values for such a constant that might be compatible with life.

In the case of the cosmological constant, we would have to consider both the Range A mentioned by these scientific papers (plus or minus 300 times) and also a vastly larger Range B representing possible values for the cosmological constant. The cosmological constant is determined by various quantum contributions to the vacuum energy density, and physicists have long told us that these contributions should be enormous. Calculations based on quantum mechanics indicate that the cosmological constant should actually be 1060 or 10120 times larger than it is. This is the problem (discussed here) called the “vacuum catastrophe” problem, the problem that reality is not matching theoretical predictions.

So the Range B for the cosmological constant should be any value between 0 and a value 1060 times stronger than its value in our universe. In a random universe the energy density of a vacuum could be anywhere between nothing and the energy density of a neutron star. In this case the Range A (a value between the cosmological constant's value in our universe and a value 300 times greater) is only a tiny fraction of the Range B – less than a millionth of a billionth.

So far from showing that “there’s a decent chance that life-fostering planets could exist in a parallel universe,” the very item being considered (the cosmological constant or vacuum energy density) is a reason for thinking that there would be less than one chance in a million billion of a random universe having properties compatible with life.

Fallacy 2: Assuming That a Universe's Habitability Depends On Only One Factor

The habitability of a universe depends on a very large number of factors, including all of these:

  • the strength of the electromagnetic force
  • the strength of the strong nuclear force binding atomic nuclei together
  • the strength of the gravitational force
  • the value of Planck's constant, a constant that appears very often in nuclear equations
  • the value of the speed of light
  • the extent of the vacuum energy density or cosmological constant
  • the expansion speed of an expanding universe
  • the ratio between the absolute value of the electric charge on the proton and the absolute value of the electric charge on the electron (very precisely 1.000000000000000 in our universe, as discussed here)
  • the ratio between the mass of the proton and the mass of the electron
  • the size of primordial density fluctuations
  • suitable law of nature, such as those allowing electromagnetism
  • the amount of entropy in the universe

All of these things have to be right for a universe to be habitable, for reasons discussed here and here. Below is a table listing some of the requirements for a universe to have civilizations (see here for a discussion of each item in the table). Click on the table to see it at better resolution.


Anthropic Principle


It is therefore a great fallacy for anyone to be hearing about some study regarding one particular cosmic parameter or fundamental constant, and then saying, “Oh, so it's not so hard for a universe to be habitable.” That's rather like some young lady saying, “Okay, I've got a good hairstyle, now I've got a good chance of becoming a movie star.” Just as becoming a movie star has many different requirements (such as looks, a good agent, lucky breaks, connections, and acting talent), having a universe compatible with life has many different requirements.

Fallacy 3: Assuming That a Habitable Universe Equals a Good Chance of a Planet with Intelligent Life

It is important not to confuse necessary conditions and sufficient conditions. A necessary condition is some condition that must be met in order for some thing to occur. A sufficient condition is something that will guarantee that such a thing will occur. For example, buying a lottery ticket is a necessary condition for winning a lottery jackpot, but not at all a sufficient condition for such a thing. Having your head cut off is not a necessary condition for death, but it is a sufficient condition for death, guaranteeing that someone will die.

In regard to the appearance of intelligent life on a planet, a habitable universe is a necessary condition for such an appearance, but not at all a sufficient condition for such a thing. Beyond the many conditions for a habitable universe, there are many additional conditions that must be met for life to get started in any universe: (1) the appearance of a genetic code; (2) the appearance at one spot of more than 100,000 base pairs achieving a functional end allowing a cell to reproduce; (3) the appearance of a molecule like DNA; (4) the appearance of a cell membrane. Then there are many additional improbable conditions that must be met for life to arise to the state of multicellular complexity and intelligence. These additional conditions are so steep that they might never occur in any of a million random universes, even if they all happened to be habitable.

There are many highly improbable conditions that must be met for any random universe to be either life-compatible or compatible with the existence of stars. For reasons discussed in this post, with overwhelming likelihood a random universe would be both lifeless and light-less. The bottom line on the cosmological constant or vacuum energy density is that it is one of many needles that must be threaded for you to have a universe compatible with life, one of many distant target bulls-eyes that must be hit to end up with a universe compatible with the existence of intelligent life.  


cosmic finetuning