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Swedish Scientist Suggests That There Is Only One Earth (blastingnews.com)
MarkWhittington writes: The conventional wisdom has been among scientists is that a myriad of Earth-like planets exist in the universe, some of which have to be the abode of life, even intelligent life. However, Astrophysicist Erik Zackrisson from Uppsala University in Sweden has run a computer simulation of the universe, incorporating what we know about exoplanets thanks to the Kepler Space Telescope, the laws of physics, and the state of the early universe. The computer simulation came up with exactly one Earth, which is to say the one we live on. Every other planet in the universe does not have the conditions necessary to sustain life. Indeed, strictly speaking, Earth itself should not exist, according to the computer model, according to the story in Discover Magazine.
If earth is such an uncommon place to live in, then maybe we, in fact, are the extremophiles
If this is accurate this is good news. One of the standard explanations for the Fermi Paradox is that Earth-like planets are very rare https://en.wikipedia.org/wiki/Rare_Earth_hypothesis. You may ask why this is good news? The reason is that something is making civilizations rare. We don't see any signs of major civilizations, either in terms of visits, radio waves, or most importantly, megastructures and large-scale engineering projects. At this point, we've looked at 100,000 nearby galaxies and essentially none of them show signs of a highly advanced civilization in terms of energy use http://www.universetoday.com/119931/100000-galaxies-and-no-obvious-signs-of-life/.
The standard explanation for this is that there is some "Great Filter" which is making civlizations rare https://en.wikipedia.org/wiki/Great_Filter. If this is something in our past (e.g. habitable planets are rare, it is tough for life to evolve, it is hard to get those last few steps to necessary levels of intelligence, etc.) then we don't need to worry. But if it is something in our future, something that civilizations do to wipe themselves(e.g. nuclear war, bad nanotech) out then we're in trouble. We need to figure this out soon, since if there is a future Filter then it likely occurs very close to our current tech level.
Every piece of evidence for early filters should make us breathe more easily since it makes late filters less necessary. Unfortunately in the last few years, almost all new evidence has been in the other direction: we've found lots of planets and it looks like even small, rocky planets are common. So this is a refreshing piece of news. However, I'm very skeptical of it. First, it seems to go against other similar studies suggesting that as many as 1/3rd of stars may have an Earth-like planet (see e.g. here http://www.universetoday.com/119931/100000-galaxies-and-no-obvious-signs-of-life/) and they appear in order to be getting this result in part to be using an extremely narrow notion of what a habitable planet would look like.
If I recall correctly, we don't yet have the capability to detect Earth sized planets. They are just barely out of our detection range. However, when we were able to detect super-Jupiter sized planets, we found a lot of them. As our detection size shrinks, the number of planets found keeps growing. If this holds up, then in when we finally get down to being able to detect Earth-sized planets, things could get interesting.
Of course, then there are moons. Imagine a solar system like our own, but with Jupiter where we are. Jupiter wouldn't be habitable, but Europa might be. A large moon orbiting a gas giant might be able to sustain life and all we'd see from here (at the moment) is "gas giant in the habitable zone, move on."
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All this speculation is pretty silly IMO, because you're trying to draw conclusions about possible civilizations far more advanced than ours, using a ridiculously small and limited amount of data from a civilization that hasn't even really left its own planet yet, except for a few primitive robotic probes within its system and one manned mission to its nearby moon for rock collecting. We haven't even visited our nearest neighboring system.
We have no idea how many habitable planets are out there, because we can't even detect them. All the exoplanets we've seen have been big and very close to their stars, because that's what our limited technology allows us to see. We would not be able to see an Earth in orbit around Alpha Centauri, much less a much farther star. 20 years ago, we didn't even know definitively about any exoplanets at all, but when we developed the capability of seeing "hot Jupiters" suddenly we started seeing hundreds of them. Most likely, there's an enormous number of Earth-sized planets out there, we just can't see them yet.
The search for radio waves is dumb. We don't even use high-powered radio waves any more, we only did for a very brief time, and radio is very hard to detect over large distances due to the Inverse Square Law. The whole SETI search seems to be based on the silly idea that ETs are out there, working their asses off to build the biggest radio transmitters they possibly can and then devoting all their energy to powering them, just so they can point these transmitters at us to send us a signal. We don't do that, so why do we assume anyone else is going to?
The megastructure thing is pretty silly too: a Dyson sphere (or better yet, a Dyson swarm which is much more realistic) wouldn't be easily detectable by us because it'd be blocking all the star's light, and would only be detectable by IR radiation. Are we even actively looking for such things? And would we be able to detect them?
Honestly, even if there were a Star Trek TNG-level civilization out there in the Delta Quadrant, we wouldn't be able to see it. It's too far away, and we wouldn't be able to detect their technology. There's a lack of signs of civilizations because we do not have the capability of seeing them, and we haven't put that much effort into looking, and certainly not into leaving our star system to check out neighboring systems. It's a lot like living on an island and concluding there's no other civilization out there because you haven't seen any come visit you, when you haven't even bothered building a boat and looking for yourself.
Actually, according to Dr. Drake, the inventor of the Drake Equation, founder of SETI, Earth is becoming less visible all the time. The satellites you talk about aren't pointed out into space, they are pointed towards Earth. We have also switched from analog to digital transmissions, so essentially everything we're transmitting at this point is indistinguishable from noise. Broadcasting large amounts of energy into the universe in analog is not something that we can expect other civilizations to do for a very long time, if our own civilization is any guide. Not only that, but the Sun also produces a fair amount of radio-frequency radiation, so there's a pretty high noise floor. Even when we're trying to talk to Mars, the SNR is miserable.
The odds against detecting extraterrestrial transmissions, or extraterrestrials detecting us, are so insurmountably vast as to defy description. I think that Dr. Drake should accept the logical conclusions of his statements and end the SETI project. We have met the Great Filter and he is us.
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Well, a lot of the language we're using to talk about this is unsatisfyingly vague. What does it mean that "the Earth should not exist"? And especially "strictly speaking"; people misuse that phrase the way they misuse "literally" -- i.e. to mean exactly the opposite of what it actually does.
If the model strictly speaking precludes the existence of the Earth, then the model was constructed wrongly. But what if the model simply predicts that the most likely number of Earth-like planets is zero? That would not, strictly speaking, preclude the Earth existing. Presumably the next most likely number of Earths would be one, followed by two etc.
In any case I have some experience with models of complex systems about which data is somewhat spotty -- in my case zoonotic diseases, which depend on all kinds of things which we don't have very good data about. So we run them with suppositions, which we dignify by calling "parameters". The thing about such models is that they're mainly useful in generating research questions than making predictions. We might not know exactly how quickly a virus amplifies inside a disease vector like a mosquito; if the model suggests that human transmissions go up rapidly with shorter amplification times, then that becomes a research priority. It can't tell you that if zika virus establishes itself in Miami this year that we'll get 22 cases.
It seems to me that we're at an analogous place with models of exosolar planets. We've only been detecting them for a few years, so while it's a reasonable starting point to assume that they're representative of planets in the universe as a whole, that isn't necessarily true. Indeed it's possible we'll never be able to observe a representative sample of planets.
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