[BLANK_AUDIO] If there are intelligent civilizations out
there, obviously We want to try and communicate with them. And there have been past attempts to send
messages to alien civilizations. Let's look at a few of these efforts. The earliest message to be sent on a
spacecraft were plaques sent On the Pioneer Ten and 11 space craft in
1972 and 1973. They had a very simple plaque on them that
showed an image of a man and A woman, and also the location of our star
system. So that if the spacecraft were ever found
by alien intelligences, they would have Some idea of what we looked like and where
we had originated the spacecraft. In 1977, the two Voyager spacecraft,
Voyager One and Two that Are now leaving the solar system, also had
records placed on them. These records contained images and music
of planet Earth, Pictures of different locations in
different countries on the Earth. And music from different cultures from
around the world to Give aliens some idea of culture,
civilization on our home planet. Carl Sagan, who was one of the people
instrumental in Developing these records and determining
what their content might be. Said of these records, the spacecraft were
being Counted and the record played only if
there Are advanced space-faring civilizations in
interstellar space. But the launching of this bottle into the
cosmic Ocean says something very hopeful about
life on this planet. Other attempts have also been made, so we
sent messages on Spacecraft, we've also sent radio messages
into space using our radio telescopes. In 1974, a pixelated message was Sent from the Arecibo radio telescope in
Puerto Rico, towards the N13 star cluster. This was a binary message that when it's
interpreted In the right way, gives aliens information
about our planet. The message contained the numbers from one
to ten, the atomic numbers Of hydrogen, carbon, nitrogen, oxygen and Phosphorus, very important elements for
life. It also gave the formulas
For sugars and base pairs of nucleotides,
of the information storage system DNA. It gave the number of nucleotides in DNA
and showed A picture of the double helix of DNA as
well. And within that picture was also a figure
of A human, a number of the population of the
earth. When that message was sent, a diagram of
our Solar system, and also an image of the
Arecibo telescope. So, a diversity Of information about the civilization that
sent that message, and also about the Biology of the organisms that thought up
that message in the first place. There have been some other recent attempts
as well. In 2001, a Russian group put together a
message called the Teenage Message, which Was a message sent by school children Constructed of ideas that they had put
together. There were greetings in Russian and English and also musical compositions for
the aliens, if they ever find them. In 1999 and 2003 there was also a message
called Cosmic Call Which was a digital message containing
basic maps to complex physical concepts. A bilingual image glossary, a Rosetta
Stone of symbols And images submitted by people all over
the world. Well, there are problems with these Messages, and these plaques sent on
spacecraft. They're very unlikely to be found by
aliens. The messages that we've been sent by radio Telescopes are very short messages, and
it's very Unlikely that over such a short period of Transmission they would be picked up by
alien civilizations. And of course those spacecraft are very
small. It's very unlikely that they will be
picked Up by aliens travelling through the space
given their Small size, but these are early attempts
to Communicate with alien civilizations if
they are out there. A somewhat more problematic question that
was first raised by Physicist Enrico Fermi is called the Fermi
paradox, and this is the paradox.
If there are intelligent civilizations out
there, if there are Billions of stars with planets around them
that might have developed Intelligent civilizations, then we would
expect that perhaps by Now we would have been visited by alien
intelligences. If the Universe is 13 billion years old
then the Question is, why have we not found any
extraterrestrial intelligences? Why have they not visited our planet? And in a later lecture we'll look at some Of the reasons why there might be a Fermi
paradox. Some of the explanations for why there
might not be aliens Visiting Earth.
So what have we learned? Well, we've learned that we live in the
hope that other Civilizations are looking for us, like we
are looking for them. We've sent out numerous messages into
space, like bottles in the ocean. We've sent plaques on spacecraft, and We've transmitted messages by radio
telescopes. We still have no real evidence for
extraterrestrial civilizations. But the hunt for them and The attempt to communicate with them
continues.
