Krauss discusses the origin of life, and he assures us that the building blocks for the first living things are abundant in space. “We have continued to find in space the more sophisticated components associated with the evolution of life on Earth.” This statement includes a link to a news article. But when I follow the link and read the article, I don't find anything that backs up the claim. The linked article refers to the discovery of space chemicals, and says, “Chemicals they found in that cloud include a molecule thought to be a precursor to a key component of DNA and another that may have a role in the formation of the amino acid alanine.” But that's a giant leap away from finding “the more sophisticated components associated with the evolution of life on Earth.” The article merely discusses the discovery of distant precursors of some of the parts of the key molecules of life – rather like finding sand that is a distant precursor of the silicon chips in your computer. In fact, we have not actually found in space "the more sophisticated components associated with the evolution of life on Earth," but only some relatively simple precursors. Krauss is also on very weak ground when he discusses some speculative theory of an MIT scientist, one that has neither experiments nor observations to back it up.
Krauss attempts to rebut arguments that the fundamental constants of the universe are fine-tuned, as if some cosmic designer had chosen them. Krauss says the following:
The constants of the universe indeed allow the existence of life as we know it. However, it is much more likely that life is tuned to the universe rather than the other way around. We survive on Earth in part because Earth’s gravity keeps us from floating off. But the strength of gravity selects a planet like Earth, among the variety of planets, to be habitable for life forms like us.
Here Krauss commits the logical fallacy known as presenting a false dilemma. A false dilemma is when a reasoner speaks as if we must choose between two different things, even though the two things are not mutually exclusive. It's the type of reasoning error committed when someone says something like, “You can either be a true patriot or a Democrat – make up your mind,” without explaining why one can't be both. The false dilemma Krauss presents is the idea that we need to make a choice between the idea that the universe is fine-tuned for life and the idea that life is fine-tuned to the universe’s laws. There is not the slightest reason to make such a choice, as the two ideas are not in any way mutually exclusive. Since it is perfectly possible that we have both a universe that is fine-tuned for life, as well as biological life that is fine-tuned to the laws and realities of the universe, the second of these ideas does nothing at all to undermine the credibility of the first idea.
Krauss then discusses the issue of the fine-tuning of the cosmological constant, something I discuss in this blog post. Scientists say that because of the strange facts of quantum mechanics, the vacuum between stars should be teeming with energy, as what are called virtual particles constantly pop in and out of existence. Quantum field theory allows us to calculate how much energy there should be in the vacuum of space because of these virtual particles. The problem is that when scientists do the calculations, they get a number that is ridiculously wrong. According to this page of a UCLA astronomer, quantum field theory gives a prediction that every cubic centimeter of the vacuum should have an energy density of 1091 grams. This number is 10 followed by 90 zeroes. That is an amount trillions of times greater than the mass of the entire observable universe, which is estimated to be only about 1056 grams.
Another name for this vacuum energy density is the cosmological constant. We know that this cosmological constant is not the ridiculously high number predicted by physicists, but some some very, very low number (although apparently non-zero). Scientists speculate that there may be some “accidental cancellation” of all these strange quantum factors that leaves us with a cosmological constant very close to zero. But in order for you to have that, it would have to be an astonishingly improbable coincidence – kind of like the coincidence you would have if you added up all the purchases of everyone in China, and subtracted from them all of the earnings of every one in the United States, and ended up with a number less than 100 dollars. We would not expect that such a lucky coincidence would occur in even 1 in a billion trillion quadrillion random universes, as it requires fine-tuning to more than one 1 part in 1,000,000,000,000,000,000,000,000,000,000,000,000.000.
Here is how Krauss attempts to explain away this “vacuum miracle” as I have called it. He says this about the cosmological constant:
Is this a clear example of design? Of course not. If it were zero, which would be “natural” from a theoretical perspective, the universe would in fact be more hospitable to life. If the cosmological constant were different, perhaps vastly different kinds of life might have arisen. Moreover, arguing that God exists because many cosmic mysteries remain is intellectually lazy in the extreme.
There are four fallacies or misstatements in this short statement, and let me carefully describe each of them.
First, it is not at all true that a cosmological constant of zero is “ 'natural' from a theoretical perspective.” As many scientists have stated, from the perspective of quantum mechanics, a small or zero cosmological constant is shockingly unnatural and a wildly improbable thing, like the chance of the total salaries of all Americans accidentally exactly or almost exactly equaling the total annual purchases of all Chinese people.
Second, let's look at Krauss' claim that the universe “would be more hospitable to life” if the cosmological constant were zero. There is actually no solid basis for this claim. The only scientific paper I can find advancing such a thesis is a very iffy speculative paper that is meekly entitled, “Preliminary Inconclusive Hint of Evidence Against Optimal Fine Tuning of the Cosmological Constant for Maximizing the Fraction of Baryons Becoming Life.” The paper can be read here. The author of this paper (Don N. Page) argues that you might have a “very small increase” in life in the universe if the cosmological constant was zero. But he seems to have no real confidence in his thesis. Referring to other scientists, he says in his paper, “Email comments by Robert Mann, Michael Salem, and Martin Rees have shown me that it is not at all clear that the very small increase in the fraction of baryons that would condense into galaxies if the cosmological constant were zero instead of its tiny observed positive value would also lead to an increase in the fraction of baryons that would go into life.” Page also points out that another scientist suggests the universe would be less habitable to life if the cosmological constant were lower.
So there is no solid basis at all for Krauss' claim that the universe “would be more hospitable to life” if the cosmological constant were zero – merely a super-iffy unsubstantiated speculation that it might be slightly more hospitable to life, a speculation other scientists dispute. Also, even if you were to get somewhat more life in a universe with a zero cosmological constant, it would still appear to be a case of enormous fine-tuning to get a cosmological constant as low as ours, given the vacuum energy density issue discussed above, and the need for all these quantum contributions to the vacuum to miraculously cancel each other out. One does not disprove a case of fine-tuning by showing that a slightly better result could have been achieved. For example, if I buy you a ticket to a hot Broadway show, and get you a seat in the middle of the second row, that is a type of fine-tuning – and you don't show it isn't fine-tuning by arguing that I could have got you a seat in the middle of the first row.
Third, in the statement above Krauss argues, “If the cosmological constant were different, perhaps vastly different kinds of life might have arisen.” No, that doesn't work to explain away this issue. The issue with the cosmological constant is that if you don't have fine-tuning to more than 1 part in 1,000,000,000,000,000,000,000, then you get no galaxies, no stars, and empty space that is a seething super-dense quantum vacuum with much more mass-energy than the density of solid steel. Under such conditions, no life of any type is possible, no matter how weird it may be.
Fourth, Krauss is using a “straw man” argument when he says that this type of reasoning is “arguing that God exists because many cosmic mysteries remain.” That's not what is going on when people use the cosmological constant (and similar cases of cosmic fine-tuning) to suggest that there is a purpose and plan behind the universe. It is instead a case of reasoning from an extreme case of fine tuning to the likelihood of a fine-tuner, not a case of arguing from the mere existence of cosmic mysteries. One would have a case of “arguing that God exists because many cosmic mysteries remain,” if one used silly reasoning such as “blacks holes and quasars are mysterious, so God probably exists.” But I am not aware of anyone using such reasoning.
Krauss then wraps up his comments with that old skeptic's slogan that extraordinary claims require extraordinary evidence, which is kind of an all purpose excuse for not believing in anything you don't want to believe, no matter how much evidence piles up. First, of all it should be noted that “extraordinary claims require extraordinary evidence” is an inappropriate slogan, similar to claims such as “Bald men require bald wives,” and “Stupid people require stupid leaders.” Imagine if I claimed that John Riser had levitated twenty feet into the air in the middle of the street. That would be an extraordinary claim, but I would not necessarily need any extraordinary evidence to show its likelihood. I could show its likelihood through ordinary, common type of evidence such as the sworn testimony of 20 reliable impartial witnesses, or live television camera footage taken by two different network television cameramen. A much better slogan is, “Extraordinary claims require good, convincing evidence, whether it be a common type of evidence or an unusual type of evidence.”
To read more about the topic of cosmic fine-tuning, with many good examples, read my blog posts here and here. The first of these posts explains the color-coded table below, which summarizes lots of requirements for the existence of civilized creatures such as us.