Back when SETI began, we expected intelligent extraterrestrials to make things easy for us.
https://www.supercluster.com/editorial/t...alien-hunt
EXCERPT: . . . Even so, it’s going to be costly for an extraterrestrial society to keep continuously transmitting at this power. Too often SETI hasn’t really considered the limitations of alien economics.
But in 2010 microwave physicist Jim Benford, his twin brother and science-fiction author Gregory Benford, and Jim’s son, NASA astronomer Dominic Benford, wrote a paper regarding the cost optimization of SETI signals. In other words, exploring how costly interstellar, and indeed intergalactic, signals are in terms of energy and resource, and what options aliens have for transmitting as inexpensively as possible. They concluded that short-duration pulsed beacons, perhaps cycling back and forth between different stars, was the way to go.
[...] “We saw Jim a few months previously in California, where we talked to him about it,” says Garrett. “He’s worked on these very high-powered radio transmitters, so we asked him about the feasibility of creating something with these large powers, and he thinks we can get quite close to those powers with our current technology.”
But here’s the rub: it’s unlikely that an extragalactic signal would be in the form of a message, thinks Benford. There are a number of reasons why...
[...] Intriguingly, detecting an extragalactic SETI signal wouldn’t just tell us that we’re not alone in the universe. It would also tell us about how technological life develops because the amount of power required would need a particular type of society.
In 1964, the Soviet radio astronomer Nikolai Kardashev developed an energy scale that he believed extraterrestrial civilizations could be measured by, and it’s a scale that has caught hold of the imagination ever since. A type I Kardashev civilization is able to harness and consume all the energy available to it on a single planet, approximately 10^16 watts, give or take depending upon the planet and the star it orbits. (Note that humankind has not yet achieved type I status.) A type II Kardashev civilization, on the other hand, is able to harness the entire power output of a star, which is approximately 10^26 watts for a Sun-like star.
A type I civilization would have to use all its energy to maintain an intergalactic beacon. For a type II civilization, however, it would be just a fraction of its energy budget.
“You would expect that beacons that are really powerful would come from a Kardashev type II society,” says Garrett.
So, the detection of an extraterrestrial signal from another galaxy would be very strong evidence that the Kardashev scale is indeed a real trajectory for technological life, and that it is possible to reach at least type II, perhaps by building a Dyson sphere around a star. (Type III would involve interstellar travel, and the ability to harness the energy output of an entire galaxy.)
There’s one other corollary to all this. If we detect a signal from technologically intelligent life in our galaxy, then because of the light travel time, the signal would be hundred, thousands, or tens of thousands of years old in the worst-case scenario.
Especially for the closer stars, it is eminently possible that the senders would still be around. For extragalactic SETI, however, the signals will be many millions, even billions, of years old. Could societies survive that long, or would we be receiving a signal from the ghosts of the past? (MORE - missing details)
https://www.supercluster.com/editorial/t...alien-hunt
EXCERPT: . . . Even so, it’s going to be costly for an extraterrestrial society to keep continuously transmitting at this power. Too often SETI hasn’t really considered the limitations of alien economics.
But in 2010 microwave physicist Jim Benford, his twin brother and science-fiction author Gregory Benford, and Jim’s son, NASA astronomer Dominic Benford, wrote a paper regarding the cost optimization of SETI signals. In other words, exploring how costly interstellar, and indeed intergalactic, signals are in terms of energy and resource, and what options aliens have for transmitting as inexpensively as possible. They concluded that short-duration pulsed beacons, perhaps cycling back and forth between different stars, was the way to go.
[...] “We saw Jim a few months previously in California, where we talked to him about it,” says Garrett. “He’s worked on these very high-powered radio transmitters, so we asked him about the feasibility of creating something with these large powers, and he thinks we can get quite close to those powers with our current technology.”
But here’s the rub: it’s unlikely that an extragalactic signal would be in the form of a message, thinks Benford. There are a number of reasons why...
[...] Intriguingly, detecting an extragalactic SETI signal wouldn’t just tell us that we’re not alone in the universe. It would also tell us about how technological life develops because the amount of power required would need a particular type of society.
In 1964, the Soviet radio astronomer Nikolai Kardashev developed an energy scale that he believed extraterrestrial civilizations could be measured by, and it’s a scale that has caught hold of the imagination ever since. A type I Kardashev civilization is able to harness and consume all the energy available to it on a single planet, approximately 10^16 watts, give or take depending upon the planet and the star it orbits. (Note that humankind has not yet achieved type I status.) A type II Kardashev civilization, on the other hand, is able to harness the entire power output of a star, which is approximately 10^26 watts for a Sun-like star.
A type I civilization would have to use all its energy to maintain an intergalactic beacon. For a type II civilization, however, it would be just a fraction of its energy budget.
“You would expect that beacons that are really powerful would come from a Kardashev type II society,” says Garrett.
So, the detection of an extraterrestrial signal from another galaxy would be very strong evidence that the Kardashev scale is indeed a real trajectory for technological life, and that it is possible to reach at least type II, perhaps by building a Dyson sphere around a star. (Type III would involve interstellar travel, and the ability to harness the energy output of an entire galaxy.)
There’s one other corollary to all this. If we detect a signal from technologically intelligent life in our galaxy, then because of the light travel time, the signal would be hundred, thousands, or tens of thousands of years old in the worst-case scenario.
Especially for the closer stars, it is eminently possible that the senders would still be around. For extragalactic SETI, however, the signals will be many millions, even billions, of years old. Could societies survive that long, or would we be receiving a signal from the ghosts of the past? (MORE - missing details)