The show examines evidence of what ufology calls "trace cases", where
physical material from a strange encounter is analyzed to determine if
it is evidence of an alien contact.
An extraterrestrial
civilization may choose to communicate with humanity by means of
artifacts or probes rather than by radio, for various reasons. While
probes may take a long time to reach the Solar System, once there they
would be able to hold a sustained dialogue that would be impossible
using radio from hundreds or thousands of light-years away. Radio would
be completely unsuitable for surveillance and continued monitoring of a
civilization, and should an extraterrestrial civilization wish to
perform these activities on humanity, artifacts may be the only option
other than to send large, crewed spacecraft to the Solar System.
Although
faster-than-light travel is being seriously considered by physicists
including Miguel Alcubierre and Michio Kaku, Tough speculates that the
enormous amount of energy required to achieve such speeds under
currently proposed mechanisms means that robotic probes traveling at
conventional speeds will still have an advantage for various
applications. 2013 research at NASA's Johnson Space Center, however,
shows that faster-than-light travel with the Alcubierre drive requires
dramatically less energy than previously thought, needing only about 1
metric ton of mass-energy to move a spacecraft at 10 times the speed of
light, in contrast to previous estimates that stated that only a
Jupiter-mass object would contain sufficient energy to power a
faster-than-light spacecraft.[note 1]
According to Tough, an
extraterrestrial civilization might want to send various types of
information to humanity by means of artifacts, such as an Encyclopædia
Galactica, containing the wisdom of countless extraterrestrial cultures,
or perhaps an invitation to engage in diplomacy with them. A
civilization that sees itself on the brink of decline might use the
abilities it still possesses to send probes throughout the galaxy, with
its cultures, values, religions, sciences, technologies, and laws, so
that they may not die along with their civilization.
Freitas
finds numerous reasons why interstellar probes may be a preferred method
of communication among extraterrestrial civilizations wishing to make
contact with Earth. A civilization aiming to learn more about the
distribution of life within the galaxy might, he speculates, send probes
to a large number of star systems, rather than using radio, as one
cannot ensure a response by radio but can (he says) ensure that probes
will return to their sender with data on the star systems they survey.
Furthermore, probes would enable the surveying of non-intelligent
populations, or those not yet capable of space navigation (like humans
before the 20th century), as well as intelligent populations that might
not wish to provide information about themselves and their planets to
extraterrestrial civilizations. In addition, the greater energy required
to send living beings rather than a robotic probe would, according to
Michaud, be only used for purposes such as a one-way migration.
Freitas
points out that probes, unlike the interstellar radio waves commonly
targeted by SETI searches, could store information for long, perhaps
geological, timescales, and could emit strong radio signals
unambiguously recognizable as being of intelligent origin, rather than
being dismissed as a UFO or a natural phenomenon. Probes could also
modify any signal they send to suit the system they were in, which would
be impossible for a radio transmission originating from outside the
target star system. Moreover, the use of small robotic probes with
widely distributed beacons in individual systems, rather than a small
number of powerful, centralized beacons, would provide a security
advantage to the civilization using them. Rather than revealing the
location of a radio beacon powerful enough to signal the whole galaxy
and risk such a powerful device being compromised, decentralized beacons
installed on robotic probes need not reveal any information that an
extraterrestrial civilization prefers others not to have.
Given
the age of the Milky Way galaxy, an ancient extraterrestrial
civilization may have existed and sent probes to the Solar System
millions or even billions of years before the evolution of Homo sapiens.
Thus, a probe sent may have been nonfunctional for millions of years
before humans learn of its existence. Such a "dead" probe would not pose
an imminent threat to humanity, but would prove that interstellar
flight is possible. However, if an active probe were to be discovered,
humans would react much more strongly than they would to the discovery
of a probe that has long since ceased to function.
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