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:
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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