Lesson 64: The Search for Extraterrestrial Intelligence
In this lesson, we will discuss the search for extraterrestrial intelligence.
We will learn about the Drake Equation, which summarizes the factors that
determines how many civilizations there are in our galaxy we might contact. We
will also look at efforts being made to search for alien civilizations by
listening for radio signals.
SETI is the Search for ExtraTerrestrial Intelligence. Considering scientists
have not yet even determined whether microbial life can exist beyond Earth,
everything involving the search for alien civilization is theoretical.
In 1961,
astronomer Frank Drake came up with an equation called the Drake Equation to
summarize factors that would determine the number of civilizations we could
contact.
A slightly simplified form is:
The number of civilizations in the Milky Way galaxy whose electromagnetic
emissions are detectable is equal to the number of habitable planets in the
galaxy, multiplied by the fraction of those planets that have life, multiplied
by the fraction that have had a civilization at some point, multiplied by the
fraction that have a civilization at this moment.
The number of habitable planets would seem to
be a high number, maybe more than 100 billion, based on studies showing that
Earth-size planets are common and many are in habitable zones around their
stars. The fraction of habitable planets that have life, however, is unknown as
we have never found solid evidence of life on other worlds.
Life on Earth arose quickly,
but Earth was already 4.5 billion years old before life became intelligent
enough to form civilizations. This might suggest that producing a civilization
is very difficult even when life is present.
Scientists search for alien civilizations using large radio telescopes that
search for alien radio signals. Funding such programs is controversial. While
there have been stories and myths about UFOs and alien life, there is no proof
of alien life currently supported by any scientific evidence publicly available.
Today, radio signals emitted and
monitored by large SETI telescopes have been set up that
would detect if any alien life sent out radio signals similar to ours.