The plot includes two future systems. The Allen Telescope Array, named after Microsoft cofounder Paul Allen, is
based on using many small scanning dishes rather than one or a small number of large dishes, with thirty-two of the
dishes scheduled to be online in 2005.When all of its 350 dishes are operational (projected in 2008), it will be
equivalent to a 2½-acre dish (10,000 square meters). It will be capable of listening to up to 100 million frequency
channels simultaneously, and able to cover the entire microwave spectrum. One of its intended tasks
will be to scan
millions of stars in our galaxy. The project relies on intelligent computation that can extract highly accurate signals
from many low-cost dishes.
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Ohio State University is building the Omnidirectional Search System, which relies on intelligent computation to
interpret signals from a large array of simple antennas. Using principles of interferometry (the study of how signals
interfere with each other), a high-resolution image of the entire sky can be computed from the antenna data.
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Other
projects are expanding the range of electromagnetic frequency, for example, to explore
the infrared and optical
ranges.
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There are six other parameters in addition to the three shown in the chart on the previous page—for example,
polarization (the plane of the wavefront in relation to the direction of the electromagnetic waves). One of the
conclusions we can draw from the above graph is that only very thin slices of this nine-dimensional "parameter space"
have been explored by SETI. So, the reasoning goes, we should not be surprised that we have not yet uncovered
evidence of an ETI.
However, we are not just searching for a single needle. Based on the law of accelerating returns, once an ETI
reaches primitive mechanical technologies, it is only a few centuries before it reaches the vast capabilities I've
projected for the twenty-second century here on Earth. Russian astronomer N. S. Kardashev describes a "type II"
civilization as one that has harnessed the power of its star for communication using electromagnetic radiation (about 4
°
10
26
watts, based on our sun).
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According to my projections (see chapter 3), our civilization will reach that level by
the twenty-second century. Given that the level of technological development of the many civilizations projected by
many SETI theorists should be spread out over
vast periods of time, there should be many greatly ahead of us. So there
should be many type II civilizations. Indeed, there has been sufficient time for some of these civilizations to have
colonized their galaxies and achieve Kardashev's type III: a civilization that has harnessed the energy of its galaxy
(about 4
°
10
37
watts, based on our galaxy). Even a single advanced civilization should be emitting billions or trillions
of "needles"—that is, transmissions representing a vast number of points in the SETI parameter space as artifacts and
side effects of its myriad information processes. Even with the thin slices of the parameter space scanned by the SETI
project to date, it would be hard
to miss a type II civilization, let alone a type III. If we then factor in the expectation
that there should be a vast number of these advanced civilizations, it is odd that we haven't noticed them. That's the
Fermi Paradox.
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