I guess this is very bad news, from a Fermi Paradox perspective. The more earth-like planets we see, the more likely it is that the “great filter” is on the other side of where we are now.
Why is this evidence that the “great filter” is ahead of us? How does seeing this distinguish between what you said and it being rare for life (especially intelligent life) to evolve, even in earth-like planets?
EDIT: I do see how it increases the chance of it being ahead of us. Since the observation “there are only rarely earth-like planets” would support the “great filter” being behind us, the observation “there are often earth-like planets” has to support it being in front of us.
Only if your beliefs prior to this discovery included any significant weight for an idea something like “A mathematically important factor in the Great Filter is likely to be a lack of roughly Earth-sized planets in the potential liquid water orbital zone of stars roughly the size of our sun.”
The Fermi paradox is that estimating various values makes it look likely that there’s other life in the galaxy. One possible reason that there isn’t is a lack of Earth-like planets. Another reason is the great filter. As such, finding Earth-like planets is evidence for the great filter. If it’s not caused by lack of Earth-like planets, then all the probability we assigned to that hypothesis has to go somewhere else, and some of it will end up at the great filter.
Right. And if you assigned very, very low probability to the hypothesis “there is a lack of Earth-like planets”, then there is nothing or next-to-nothing to reassign to other hypotheses, and thus no (discernible) increase in the probability of the Great Filter being ahead of us, and thus there is no “very bad news”. Thus, “Only if your beliefs prior to this discovery . . . ”
So, the question is, was it reasonable before this discovery to expect that there were very few Earth-like planets? Well, what does “Earth-like” mean? In this case, it means only that the planet is within a factor of 2.4 in radius of Earth and is in the “habitable zone” (that is, an orbit able to sustain liquid water) of a Sun-like star (implicitly defined in this case as within about ±25% of the Sun’s radiance). So given the incredibly broad definition of “Earth-like” being used in this case, our solar system already contains three Earth-like planets.
Now, it is possible that Earth’s solar system was a triple hyper-rare accident. But there was no reason, from either theories of planetary formation or actual observations, to expect so. So my prior probability assigned to the hypothesis “there is a lack of Venus-like planets in the galaxy” was difficult to discern from zero.
Now, it is possible that Earth’s solar system was a triple hyper-rare accident.
Planets may not be independent. Perhaps there’s something that made rocky planets more likely to form in our solar system, and thus we ended up with about three, and most solar systems ended up with none.
Well, what does “Earth-like” mean? In this case, it means only that the planet is within a factor of 2.4 in radius of Earth and is in the “habitable zone” (that is, an orbit able to sustain liquid water) of a Sun-like star (implicitly defined in this case as within about ±25% of the Sun’s radiance). So given the incredibly broad definition of “Earth-like” being used in this case, our solar system already contains three Earth-like planets.
But do all three of those have temperatures of 72 degrees F?
Read the news carefully. Kepler-22b theoretically could have a temperature of 72 degrees F, sure . . . if it has an Earth-level greenhouse effect. But we don’t have any measurements of its temperature, and we don’t know the thickness or composition of its atmosphere.
Kepler-22b could have wound up with a Venus-type atmosphere, much thicker than Earth’s and high in carbon dioxide, and have a temperature far, far above 72 degrees F. It might have lost its atmosphere due to some early event and have radical temperature changes around the estimated −11 degrees C average. It might have an atmosphere that is thick and convective but transparent to infrared, with high albedo in the visible range, which results in it being an even-temperature ball even cooler than the no-atmosphere estimates make.
And that’s just atmospheric effects. Earth-type atmosphere combined with Venus-type or Moon-type rotation leaves you with an average of 72 degrees F, sure . . . but every spot alternately freezing and baking.
All “Earth-like” means in reference to Kepler-22b is that it’s within a factor of 2.4 in radius of Earth and is in the “habitable zone” (that is, an orbit able to sustain liquid water ore not depending on the local planetary characteristics) of a Sun-like star (implicitly defined in this case as within about ±25% of the Sun’s radiance). And by that definition, Venus and Mars both qualify as “Earth-like”.
I guess this is very bad news, from a Fermi Paradox perspective. The more earth-like planets we see, the more likely it is that the “great filter” is on the other side of where we are now.
Why is this evidence that the “great filter” is ahead of us? How does seeing this distinguish between what you said and it being rare for life (especially intelligent life) to evolve, even in earth-like planets?
EDIT: I do see how it increases the chance of it being ahead of us. Since the observation “there are only rarely earth-like planets” would support the “great filter” being behind us, the observation “there are often earth-like planets” has to support it being in front of us.
Only if your beliefs prior to this discovery included any significant weight for an idea something like “A mathematically important factor in the Great Filter is likely to be a lack of roughly Earth-sized planets in the potential liquid water orbital zone of stars roughly the size of our sun.”
The Fermi paradox is that estimating various values makes it look likely that there’s other life in the galaxy. One possible reason that there isn’t is a lack of Earth-like planets. Another reason is the great filter. As such, finding Earth-like planets is evidence for the great filter. If it’s not caused by lack of Earth-like planets, then all the probability we assigned to that hypothesis has to go somewhere else, and some of it will end up at the great filter.
Right. And if you assigned very, very low probability to the hypothesis “there is a lack of Earth-like planets”, then there is nothing or next-to-nothing to reassign to other hypotheses, and thus no (discernible) increase in the probability of the Great Filter being ahead of us, and thus there is no “very bad news”. Thus, “Only if your beliefs prior to this discovery . . . ”
So, the question is, was it reasonable before this discovery to expect that there were very few Earth-like planets? Well, what does “Earth-like” mean? In this case, it means only that the planet is within a factor of 2.4 in radius of Earth and is in the “habitable zone” (that is, an orbit able to sustain liquid water) of a Sun-like star (implicitly defined in this case as within about ±25% of the Sun’s radiance). So given the incredibly broad definition of “Earth-like” being used in this case, our solar system already contains three Earth-like planets.
Now, it is possible that Earth’s solar system was a triple hyper-rare accident. But there was no reason, from either theories of planetary formation or actual observations, to expect so. So my prior probability assigned to the hypothesis “there is a lack of Venus-like planets in the galaxy” was difficult to discern from zero.
Planets may not be independent. Perhaps there’s something that made rocky planets more likely to form in our solar system, and thus we ended up with about three, and most solar systems ended up with none.
But do all three of those have temperatures of 72 degrees F?
Read the news carefully. Kepler-22b theoretically could have a temperature of 72 degrees F, sure . . . if it has an Earth-level greenhouse effect. But we don’t have any measurements of its temperature, and we don’t know the thickness or composition of its atmosphere.
Kepler-22b could have wound up with a Venus-type atmosphere, much thicker than Earth’s and high in carbon dioxide, and have a temperature far, far above 72 degrees F. It might have lost its atmosphere due to some early event and have radical temperature changes around the estimated −11 degrees C average. It might have an atmosphere that is thick and convective but transparent to infrared, with high albedo in the visible range, which results in it being an even-temperature ball even cooler than the no-atmosphere estimates make.
And that’s just atmospheric effects. Earth-type atmosphere combined with Venus-type or Moon-type rotation leaves you with an average of 72 degrees F, sure . . . but every spot alternately freezing and baking.
All “Earth-like” means in reference to Kepler-22b is that it’s within a factor of 2.4 in radius of Earth and is in the “habitable zone” (that is, an orbit able to sustain liquid water ore not depending on the local planetary characteristics) of a Sun-like star (implicitly defined in this case as within about ±25% of the Sun’s radiance). And by that definition, Venus and Mars both qualify as “Earth-like”.