The implications of cosmic silence

cosmos

Credit: CC0 Public Domain

The universe is incomprehensibly vast, with billions of other
planets circling billions of other stars. The potential for
intelligent life to exist somewhere out there should be
enormous.

So, where is everybody?

That’s the Fermi paradox in a nutshell. Daniel Whitmire, a
retired astrophysicist who teaches mathematics at the
University of Arkansas, once thought the cosmic silence
indicated we as a lagged far behind.

“I taught astronomy for 37 years,” said Whitmire. “I used to
tell my students that by statistics, we have to be the dumbest
guys in the galaxy. After all we have only been technological
for about 100 years while other civilizations could be more
technologically advanced than us by millions or billions of
years.”

Recently, however, he’s changed his mind. By applying a
statistical concept called the principle of mediocrity – the
idea that in the absence of any evidence to the contrary we
should consider ourselves typical, rather than atypical –
Whitmire has concluded that instead of lagging behind, our
species may be average. That’s not good news.

In a paper published Aug. 3 in the International Journal of
Astrobiology
, Whitmire argues that if we are typical, it
follows that species such as ours go extinct soon after
attaining technological knowledge. (The paper is also available
on
Whitmire’s website
.)

The argument is based on two observations: We are the first
technological species to evolve on Earth, and we are early in
our technological development. (He defines “technological” as a
biological species that has developed electronic devices and
can significantly alter the planet.)

The first observation seems obvious, but as Whitmire notes in
his paper, researchers believe the Earth should be habitable
for animal life at least a billion years into the future. Based
on how long it took proto-primates to evolve into a
technological species, that leaves enough time for it to happen
again up to 23 times. On that time scale, there could have been
others before us, but there’s nothing in the geologic record to
indicate we weren’t the first. “We’d leave a heck of a
fingerprint if we disappeared overnight,” Whitmire noted.

By Whitmire’s definition we became “technological” after the
industrial revolution and the invention of radio, or roughly
100 years ago. According to the principle of mediocrity, a bell
curve of the ages of all extant technological civilizations in
the universe would put us in the middle 95 percent. In other
words, technological civilizations that last millions of years,
or longer, would be highly atypical. Since we are first, other
typical technological civilizations should also be first. The
principle of mediocrity allows no second acts. The implication
is that once species become technological, they flame out and
take the biosphere with them.

Whitmire argues that the principle holds for two standard
deviations, or in this case about 200 years. But because the
distribution of ages on a bell curve skews older (there is no
absolute upper limit, but the age can’t be less than zero), he
doubles that figure and comes up with 500 years, give or take.
The assumption of a bell-shaped curve is not absolutely
necessary. Other assumptions give roughly similar results.

There’s always the possibility that we are atypical and our
species’ lifespan will fall somewhere in the outlying 5 percent
of the bell curve. If that’s the case, we’re back to the nugget
of wisdom Whitmire taught his astronomy students for more than
three decades.

“If we’re not typical then my initial observation would be
correct,” he said. “We would be the dumbest guys in the galaxy
by the numbers.”

Explore further:

Starring Intelligent Aliens

More information: Daniel P. Whitmire. Implication of our
technological species being first and early, International
Journal of Astrobiology
(2017). DOI: 10.1017/S1473550417000271

Journal reference:
International Journal of Astrobiology

Provided by: University
of Arkansas

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