Webb is finding interesting things near the noise floor, possible biosignatures. The next and bigger one should start answering questions the radio spectrum has not disclosed.
I was wondering if the seti piece was still around and it was, so I edited it a bit from the perspective of 20+ years!
Who hasn't gazed at the distant suns populating the night sky and wondered? For as long as we humans could think, we have thought about the stars and the spectacular, mysterious vistas the heavens presented to us each night. Today, the average person staring up at the beauty of the unfolding universe, might muse about how life began, whether there is other life out there, and if other distant beings share our awareness of the larger universe. Does other life and intelligence exist among this sea of stars in which we live? Many people think so. If we think deeply about these things, we might speculate on the origin, frequency and variety of life in our galaxy. We might also ask, how rare is intelligence and what are the fates and life spans of technological civilizations.
For much of our scientific history, the answers to such questions were beyond reach and consigned to the realm of speculation and fiction. This state of affairs started to change with the publication of the first realistic strategy for a search for extraterrestrial intelligence in 1959. "Searching for Interstellar Communications," by Philip Morrison and Giuseppe Cocconi, published in Nature, advocated searching nearby stars for interstellar radio signals centered on the 1420 Mhz part of the radio spectrum, known as the 'Water Hole." This naturally quiet part of the electromagnetic spectrum, allowed directed microwave transmissions over vast distances using modest power levels.
Around this time, Frank Drake, a radio astronomer at the NRAO (National Radio Astronomy Observatory), also began independently planning a SETI search. Drake conducted the first systematic interstellar search for microwave signals in 1960. This search, called project Ozma, targeted two nearby star systems and listened in the 1420 Mhz frequency range for possible signal carriers. This seminal work was the beginning of the scientific search for other intelligences in our galaxy.
While planning the first SETI conference in 1961 at Green Bank, WV, Drake conceived of a formula that could help guide the conference agenda. This simple linear equation (which appears in detail on The SETI League website, and in all modern astronomy textbooks) is used to estimate the probable number of technological civilizations that might transmit radio beacons in our galaxy. For the past forty years all of the factors used in this equation were mere speculation, guesses. However, within the present decade, we should see this situation change. The Drake equation, instead of being a vehicle for speculation, promises to become a valuable tool; it will be used to determine many probabilities and to answer fundamental questions.
New technological abilities, scientific instruments and the research programs they generate, will deal with the Drake equation in a methodical way. Let's look at each of the factors that produce the result N, the number of communicating technological civilizations in the galaxy. Furthermore, let's project ahead and try to determine what factors will be known and how accurate those estimates of the factors might be.
R* The rate of appropriate star formation is the average number of stars born each year in the galaxy. Many stars may form each year, but only a certain percentage will live long enough or can go on to become hospitable to life and evolution. Only certain stars will do, but since there are an estimated 400 billion stars in the galaxy, there will be tens of billions of candidate stars.
Using existing data and discoveries from planned space missions and instruments, this number will be known with the most certainty. Current best guess: 1.5 appropriate stars per year.
Fp The fraction of those appropriate stars that have planets. Since it is believed that planetary formation is an integral part of star formation, this number should be high. Recent extrasolar planetary discoveries indicate planets are very common. Information for determining this factor is pouring in almost monthly. Already dozens of extrasolar planets have been discovered. New detection methodologies, instruments and programs are already starting to set the outside parameters for this factor. As the database grows, overall trends should become apparent. Professional expertise, theoretical models and computer simulations will add to these predictive and detection capabilities. Reasonable conjectures on the planetary systems of more distant stars and even the entire galaxy might then be possible.
Ne The numbers of earthlike (terrestrial) planets per appropriate star. Planets must be in the zone around their star where liquid water can exist. This is the habitable area around a star, where at least it's possible for life to exist and where biospheres might form, thrive and persist.
Missions currently in the planning or development stages will place very sensitive instruments into space within this decade. These instruments will be able to detect terrestrial planets, and even biospheres, several dozens of light years distant.
Fl The fraction of the above worlds that have life. This factor currently has no known value. To a large extent it depends on the nature of life. Is life an inevitable consequence of natural processes, like the progressive formation of more complex elements in stars? The creation and mixing of complex organic molecules, amino acids and even DNA precursors, have all been observed in interstellar nebula; this appears to be a common process in the universe. How common is it for this organic sludge to form life, at least carbon-based life? We do know it happened very quickly here; life arose on Earth almost from the moment it could exist.
The fecundity of life in the galaxy is a key factor in the Drake equation. Fl is the factor to watch in the coming decade. If life is abundant, then the probability of successful SETI goes way up. If life is very rare, then the odds of finding a transmitting technological civilization are extremely small. I estimate that there are a half billion biospheres similar to Earth in the galaxy (a guess, to be sure, but my own best guess). Dividing a high-end estimate for the number of biospheres into the volume of space our galaxy occupies, results in roughly one biosphere for every 16,000 cubic light years of galactic volume. This is approximately the volume of a sphere with a radius of 16 light years. If these biospheres are randomly spaced, some, at least, should be detectable by future space-based spectroscopic analysis of extraplanetary atmospheric gases for: ratios of water vapor, free oxygen, ozone and methane, that indicate the presence of life. It is assumed the first generation of these instruments could detect the spectroscopic signature of an extrasolar biosphere over two-dozen light years distant.
Determining if other life exists at all, let alone knowing its possible frequency of occurrence, would be a monumental scientific discovery. Whenever we find new biospheres, we will use the Drake equation to estimate the number of potential homes there might be for higher life forms in the galaxy. We should then be able to determine the factor Fl with even greater accuracy over time.
