One
of the most fundamental questions that we as a civilization might ask concerns
the possibility that other intelligent beings may also inhabit our galaxy. On
November 16, 1974, a group of scientists led by Frank Drake and Carl Sagan sent
a message towards a large star cluster in the constellation of Hercules. At a
distance of 13,000 light years, the message is still a long way from getting
there. That event is considered the beginning of our search for other
civilizations.
SETI
stands for Search for Extra-Terrestrial Intelligence. The two most active organizations
doing this are the SETI Institute and the Breakthrough Listen
program. Both primarily use sophisticated radio telescopes to search for artificial
radio signals from other planets that could support life. The thinking behind
these projects is that any other intelligent civilization is likely to use
radio signals for communication and detection.
We
humans use radio for these very purposes. Civil and military airport radar
represents our most powerful radio signals. We’ve been using this technology
since World War 2, and today’s radars are far more powerful and sophisticated. They
are so powerful that they can be detected by any civilization with radio
telescope technology at the same level as our SETI searches use.
Ramiro
Saide, a Ph.D. student at the University of Manchester, led a research project
to calculate how far away our radar facilities could be detected by
civilizations at least as advanced as us. Our radio telescopes are capable of
detecting a signal like what we emit from our airport radars from 200 light
years away. There are more than 120,000 stars within 200 light-years of Earth. Although
we currently have no evidence that any of those stars are home to intelligent
aliens, we do know that they likely have some 200,000 or more planets that
orbit them. Most of those aren’t capable of supporting life as we know it, but
some may well be able to.
Saide
said of the study that our radar signals would appear “clearly artificial to
anyone watching from interstellar distances with powerful radio telescopes. These
military signals can appear up to a hundred times stronger from certain points
in space, depending on the observer’s location. Our findings suggest that radar
signals – produced unintentionally by any planet with advanced technology and
complex aviation system – could act as a universal sign of intelligent life.”
While
our efforts to detect other civilizations have not yet provided any absolute
proof of their existence, at least we know that our equipment could detect
their radar emissions. The SETI Institute and Breakthrough Listen will continue
to monitor the skies for any neighbors we might have.
Each month, I write an astronomy-related column piece
for the Oklahoman newspaper. After
it is published there, I post that same column to my blog page.
This is reprinted with
permission from the Oklahoman and www.Oklahoman.com.
