In short, only the duration of transmission matters in steady-state, which is the final L term in Drake’s famous equation. Start time does not matter.
Regarding Andrew’s predicate “given that we haven’t hard any such signals so far” in the OP: despite the high profile of SETI, almost no actual searching has occurred because the field is essentially unfunded (until Yuri Milner’s recent support). Jill Tarter analogizes the idea that we need to update our priors based on the searching to date as being equivalent to saying that there must not be very many fish in the ocean based on inspecting the contents of a single drinking glass dipped in it (that’s a rough OOM, but it’s pretty close). And that’s just searches for narrowband radio searches; other kinds of searches are far, far less complete.
And Andrew is not wrong that the amount of popular discussion of SETI has gone way down since the ’90’s. A good account of the rise and fall of government funding for SETI is Garber (1999).
I have what I think is a complete list of NASA and NSF funding since the (final) cancellation of NASA’s SETI work in 1993, and it sums to just over $2.5M (not per year—total). True, Barnie Oliver and Paul Allen contributed many millions more, but most of this went to develop hardware and pay engineers to build the (still incomplete and barely operating) Allen Telescope Array; it did not train students or fund much in the way of actual searches.
So you haven’t heard much about SETI because there’s not much to say. Instead, most of the literature is people in their space time endlessly rearranging, recalculating, reinventing, modifying, and critiquing the Drake Equation, or offering yet another “solution” to the Fermi Paradox in the absence of data.
The central problem is that for all of the astrobiological terms in the Drake Equation we have a sample size on 1 (Earth), and since that one is us we run into “anthropic principle” issues whenever we try to use it to estimate those terms.
The recent paper by Sandberg calculates reasonable posterior distributions on N in the Drake Equation, and indeed shows that they are so wide that N=0 is not excluded, but the latter point has been well appreciated since the equation was written down, so this “dissolution” to the Fermi Paradox (“maybe spacefaring life is just really rare”) is hardly novel. It was the thesis of the influential book Rare Earth and the argument used by Congress as a justification for blocking essentially all funding to the field for the past 25 years.
Actually, I would say that an equally valid takeaway from the Sandberg paper is that very large values of N are possible, so we should definitely be looking for them!
- More Here
Regarding Andrew’s predicate “given that we haven’t hard any such signals so far” in the OP: despite the high profile of SETI, almost no actual searching has occurred because the field is essentially unfunded (until Yuri Milner’s recent support). Jill Tarter analogizes the idea that we need to update our priors based on the searching to date as being equivalent to saying that there must not be very many fish in the ocean based on inspecting the contents of a single drinking glass dipped in it (that’s a rough OOM, but it’s pretty close). And that’s just searches for narrowband radio searches; other kinds of searches are far, far less complete.
And Andrew is not wrong that the amount of popular discussion of SETI has gone way down since the ’90’s. A good account of the rise and fall of government funding for SETI is Garber (1999).
I have what I think is a complete list of NASA and NSF funding since the (final) cancellation of NASA’s SETI work in 1993, and it sums to just over $2.5M (not per year—total). True, Barnie Oliver and Paul Allen contributed many millions more, but most of this went to develop hardware and pay engineers to build the (still incomplete and barely operating) Allen Telescope Array; it did not train students or fund much in the way of actual searches.
So you haven’t heard much about SETI because there’s not much to say. Instead, most of the literature is people in their space time endlessly rearranging, recalculating, reinventing, modifying, and critiquing the Drake Equation, or offering yet another “solution” to the Fermi Paradox in the absence of data.
The central problem is that for all of the astrobiological terms in the Drake Equation we have a sample size on 1 (Earth), and since that one is us we run into “anthropic principle” issues whenever we try to use it to estimate those terms.
The recent paper by Sandberg calculates reasonable posterior distributions on N in the Drake Equation, and indeed shows that they are so wide that N=0 is not excluded, but the latter point has been well appreciated since the equation was written down, so this “dissolution” to the Fermi Paradox (“maybe spacefaring life is just really rare”) is hardly novel. It was the thesis of the influential book Rare Earth and the argument used by Congress as a justification for blocking essentially all funding to the field for the past 25 years.
Actually, I would say that an equally valid takeaway from the Sandberg paper is that very large values of N are possible, so we should definitely be looking for them!
- More Here
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