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Our future, our universe, and other weighty topics

Saturday, December 3, 2016

They Put a “Science” Sticker on Their Gossamer Threads of Speculation

When you hear the phrase “tribal folklore,” you probably think of some image such as members of a primitive tribe sitting around a campfire, while someone with a necklace of bones and a feather headdress tells a story such as “Once upon a time the sun god spat out the earth.” But tribal folklore can arise and flourish in the modern halls of American universities, where there exist tribes such as the small tribe of cosmologists. Below is the story of how some tribal folklore not only started to flourish, but experienced runaway growth, like some out-of-control kudzu.

Around about 1978, cosmologists (the scientists who study the universe as a whole) were puzzled by a problem of fine-tuning. They had figured out that the expansion rate of the very early universe (at the time of the Big Bang) must have been incredibly fine-tuned, apparently to one part in ten to the sixtieth power. This dilemma was known as the flatness problem.

Enter Alan Guth, an MIT professor. Guth proposed a way to solve the flatness problem. Guth proposed that for a tiny fraction of its first second (for less than a trillionth of a trillionth of a second), the universe expanded at an exponential rate. The universe is not expanding at any such rate, but Guth proposed that after a very brief instant of exponential expansion, the universe switched back to the normal, linear expansion that it now has.

This idea was extremely far-fetched from the moment it was proposed, particularly the idea of the universe making this sudden switch so quickly. But nonetheless Guth's idea became very popular among the small tribe of cosmologists. We can call this idea Guthism, and we can call the cosmologists who adopted it Guthists.

But there was a big problem with Guthism. Its early versions (as advanced in the early 1980's) simply did not work. They had all kinds of problems. The Guthists tried to fix this. First, they got busy creating hundreds of different versions of Guthist theories, all based on the idea that the universe had undergone an instant of exponential expansion. So instead of just one Guthist theory, before long there were hundreds of variant theories.

Some of these theories indulged in runaway speculations. One variation called eternal inflation imagined that our universe was just one bubble in an infinite sea of bubble universes. The advantage of this is that no matter improbable it might be that a universe might undergo a phase of exponential expansion and then change to the regular expansion we observe, a Guthist could say that such a thing would have happened at least once in the infinite sea of bubble universes.

We must take a step back here, and categorize the scientific status of Guthism.  Guthism is sold as science; its proponents have put a "science" sticker on their gossamer threads of speculation.

However, Guthism is best described not as science, but tribal folklore. It is a species of folklore that has become popular among the very small tribe of humans called cosmologists.

Below is the basic piece of folklore behind Guthism:

At the very beginning the universe started out with just the right conditions for it to start expanding at an exponential rate. So for the tiniest fraction of a second, the universe did expand at this explosive exponential rate. Then, boom, the universe suddenly switched gears, and started expanding at the much slower, linear rate that we now observe.

There is no evidence supporting this speculation, so it is quite accurate to call it a piece of tribal folklore. The actual expansion of the universe that we observe justifies no belief other than the belief that the universe has expanded at the same linear rate that we now observe it expanding at.

But our Guthists often mislead us about whether there is evidence for their Guthist folklore. Here is a very misleading statement recently made by Guthist cosmologist Ethan Siegel:

You see, we can extrapolate the Big Bang backwards to an arbitrarily hot, dense, expanding state, and what we find is that it didn’t get infinitely hot and dense early on, but rather that — above some energy and before some very early time — there was a phase that preceded the Big Bang, and set it up. That phase, a period of cosmological inflation, describes a phase of the Universe where rather than being full of matter and radiation, the Universe was filled with energy inherent to space itself: a state that causes the Universe to expand at an exponential rate.

This is a falsehood, as the Guthist theory of cosmological inflation (that the universe once expanded at an exponential rate) is not at all something that can be derived by any type of extrapolation. Extrapolating the universe's current expansion back to the very beginning of time in no way supports the conclusion that the universe underwent an exponential expansion of the type imagined by Guthists. Saying that extrapolation leads to exponential expansion (Guthist cosmic inflation) at the universe's beginning is like saying that you can extrapolate the motion of a baseball pitcher's fastball to calculate that it will end up in the exhaust pipe of your car, because the hitter may hit the ball out of the stadium, and the ball may bounce off the parking lot asphalt, landing in your car's exhaust pipe. The scientific papers of the Guthist theorists don't use extrapolation to set up the conditions for exponential expansion; they rely instead on speculations as ornate as the exhaust pipe speculation just given.

In the same post (entitled “Is There Another 'You' Out There in a Parallel Universe?”), Siegel sinks into the kind of runaway, out-of-control folklore that Guthists like to engage in, as when he says, “There are a huge number of Universes out there — possibly with different laws than our own and possibly not — but there are not enough of them to give us alternate versions of ourselves; the number of possible outcomes grows too rapidly compared to the rate that the number of possible Universes grows.” To the contrary, we have zero evidence for the Guthist claim of exponential expansion in the early universe, and zero evidence for any other physical universe other than our own.

One of the reasons why Guthism isn't really a scientific program is that it is neither based on observations nor does it make precise predictions that we can test. A New Scientist article puts it this way:

But no measurement will rule out inflation entirely, because it doesn’t make specific predictions. “There is a huge space of possible inflationary theories, which makes testing the basic idea very difficult,” says Peter Coles at Cardiff University, UK. “It’s like nailing jelly to the wall.”

The Guthist idea of exponential expansion was originally created to try to remove the precise fine-tuning needed to have the critical density of the universe match the actual density of the universe, to sixty decimal places. The thinking was kind of like, “Ugh, we don't like fine-tuning in nature, so let's try to get rid of it.” But the Guthist cosmic inflation theory requires its own fine-tuning to work – just as much or more as the fine-tuning it was designed to remove. Judging from a recent cosmology paper, Guthist claims require not just one type of fine-tuning, but three types of fine-tuning. The paper says, “Provided one permits a reasonable amount of fine tuning (precisely three fine tunings are needed), one can get a flat enough effective potential in the Einstein frame to grant inflation whose predictions are consistent with observations.” How on Earth does it represent progress to try to get rid of one case of fine-tuning by introducing a theory that requires three cases of fine-tuning? And the estimate of three fine-tunings in the paper is probably an underestimate, as other papers I have read suggest that 7 or more precise fine-tunings are needed.

This is not theoretical progress

In terms of actually advancing human knowledge, Guthism has been a bust for cosmology, a misadventure that future cosmologists will probably look back on with disdain. We have learned nothing about reality by these unverifiable speculations that the universe underwent an instant of exponential expansion during its first second. But Guthism has been very good for cosmologists themselves. This is because Guthism provides our cosmologists with an easy way of earning a paycheck, a nice meal-ticket. The modern cosmologist is supposed to write several scientific papers every year, and writing a Guthist paper on yet another variation of cosmic inflation theory is easy work for today's cosmologist. We cannot observe anything that happened before the recombination era that happened about 380,000 years after the Big Bang. So if you are a cosmologist, you can make a nice, safe living writing speculative papers about various weird physical possibilities during the universe's first instant; and no one will be able to disprove your speculations.

Let me describe a very simple method for distinguishing between a scientist who has actually discovered something and a scientist who is indulging in speculation, perhaps just giving you a little folklore of his science tribe. After the scientist discusses his pet doctrine, you just ask him or her: “What observations or experiments forced you to believe that?” In the case of a relatively solid finding such as the Big Bang, the scientist can give a good answer, by mentioning things like the discovery that galaxies are receding away from us, and the discovery of the cosmic background radiation around 1965. But in the case of the Guthist theory of exponential expansion of the universe during only a fraction of its first second, a scientist will have no decent answer to the question of, “What observations or experiments forced you to believe that?”

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