Aliens haven’t been found because we’ve hardly looked for them: study

“Where
is everybody?”

potiros
tanarm/Shutterstock

• The universe has so many galaxies, stars, planets, and moons
  that many scientists believe intelligent aliens should exist within detectable range
  of Earth.
• Still, human searches for extraterrestrial intelligence
  have yet to detect any alien signal or “technosignature.”
• A new study suggests this may be because we’ve searched just
  0.00000000000000058% of a “cosmic haystack” in our hunt for an
  alien “needle.”
• There’s no guarantee that exhaustive searches would ever find
  aliens, though.

The cosmos almost screams with the
possibility of intelligent alien life.

Hundreds of billions of galaxies drift through the
visible universe, each one harboring hundreds of billions of
stars, and each of those stars in turn shelters roughly a handful of planets. Even if
the trillion-or-so planets in every galaxy
aren’t habitable, countless
water-rich moons orbiting these lifeless worlds might be.

And yet, in spite of these numbers, humans have yet to identify
any signals from intelligent aliens. The prescient question that
physicist Enrico Fermi posed in 1950 — “where is everybody?” — remains
unanswered.

However, an upcoming study in The Astronomical Journal, which we
learned about from MIT Technology Review,
suggests humanity has barely sampled the skies, and thus has no
grounds to be cynical.

According to the paper, all searches for extraterrestrial
intelligence, or SETI, have examined barely a swimming pool’s
worth of water from a figurative ocean of signal space.

“We haven’t really looked much,” Shubham Kanodia, a graduate student in
astronomy who co-wrote the study, said during a NASA “technosignatures”
workshop in Houston, Texas on September 26.

The study suggests that somewhere in that ocean of space — right
now, within the
Milky Way galaxy — intelligent aliens might be saying,
“hello, we are here.”

But we’d have no way of knowing, at least not yet.

Defining a ‘cosmic haystack’ in the search for aliens

An
illustration of a radio-beam-powered light sail on an alien
spacecraft.

M.
Weiss/CfA

Over the past 60 years, multiple SETI projects have looked and
continue to look for alien signals. Some scan large swaths of the
sky for powerful signals, while others target individual star
systems for weaker signals.

Yet aside from a few anomaly signals that never repeated (like
the
“Wow!” detection of 1977), these searches have turned up
empty-handed.

Kanodia and his colleagues at Penn State University wanted to
know how much of the figurative “cosmic haystack” SETI projects
have covered, and to what extent they could improve the hunt for
the alien “needle.”

The group agrees with famous SETI astronomer Jill Tarter, who
said in 2010 that it’s silly to conclude intelligent aliens do
not exist nearby just because we haven’t yet found their beacons.
Even if such signals exist and are aimed right at Earth, her
thinking goes, we’ve scanned so little of the sky and may not be
looking for the right type of signal, or for long enough, to find
them.

“Suppose I tell you there’s a cool thing happening in Houston
right now,” Kanodia said during his NASA talk. “I do not tell you
where it is. I do not tell you when it is happening. I do not
tell you what it is. Is it in a book store? Is it a music
concert? I give you absolutely no priors. It would be a difficult
thing to try and find it.”

He added: “Houston, we have a problem. We do not know what we’re
looking for … and we don’t know where to start.”

NASA/JPL-Caltech/R.
Hurt (SSC/Caltech)

In their study, Kanodia and his colleagues built a mathematical
model of what they consider a reasonably sized cosmic haystack.

Their haystack is a sphere of space nearly 33,000 light-years in
diameter, centered around Earth. This region captures the Milky
Way’s bustling core, as well as many giant globular clusters of
stars above and below our home galaxy.

They also picked eight dimensions of a search for aliens —
factors like signal transmission frequency, bandwidth, power,
location, repetition, polarization, and modulation (i.e.
complexity) — and defined reasonable limits for each one.

“This leads to a total 8D haystack volume of 6.4 ×
10¹¹⁶ m⁵Hz² s/W,” the authors
wrote.

That is 6.4 followed by 115 zeros — as MIT Technology review
described it, “a space of truly gargantuan proportions.”

How much of this haystack have we searched?

Instead
of asking, “Where is everybody?” we should be asking, “Why are we
barely looking?”

SETI
Institute

Kanodia and his colleagues then examined the past 60 years’ worth
of SETI projects and reconciled them against their haystack.

The researchers determined that humanity’s collective search for
extraterrestrials adds up to about 0.00000000000000058% of the
haystack’s volume.

“This is about a bathtub of water in all of Earth’s oceans,”
Kanodia said. “Or about a five-centimeter-by-five-centimeter
patch of land on all of Earth’s surface area.”

Those numbers make humanity’s search efforts seem feeble. But
Kanodia views it as an opportunity — especially because modern
telescopes are getting better at scanning more objects with
greater sensitivity and speed. For example, he said, a 150-minute
search this year by the Murchison Widefield Array covered a
larger percentage of the haystack than any other SETI project in
history.

“That’s the purpose of this haystack … to help better-inform
future search strategies,” Kanodia said.

He also noted that the team’s calculations assume there is only
one alien civilization within range of Earth, and not any more
than that. But more than one may exist relatively close by.

“In the ocean analogy, we do not have to drain the entire ocean
to find a fish,” he said. “In the Houston analogy, if there were
two cool things, you wouldn’t have to look as hard.”

Still, there’s no guarantee that a figurative fish or needle or
cool thing is out there at all.

Another group of scientists, this one at Oxford University,
recently took a different approach to the question of aliens.
Instead of focusing on the likelihood of finding
“technosignatures” that could be detected, they examined the
likelihood that intelligent alien life exists at all.

The Oxford researchers examined dozens of authoritative studies
about
variables in the Drake Equation. The team then analyzed the
results and calculated a bleak
2-in-5 chance that humans may be entirely alone in the Milky
Way galaxy.

There’s also a
more unsettling possibility: Perhaps aliens do exist nearby
but don’t want us to find them.