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By working faithfully eight hours a day, you may eventually get to be boss and work twelve. -- Robert Frost
Then he's doing it wrong. (Score:5, Insightful)
If his model says that Earth should not exist, then there's something wrong with his model.
Also, considering how life thrives even in hostile environments here on Earth, it's simply a mathematical impossibility that there are no other planets in the universe capable of supporting some kind of life.
Re:Then he's doing it wrong. (Score:2, Insightful)
That's not what he's saying. He says that earths are statistically rare. That doesn't make any predictions on the amount of life in the universe that might exist on not-earth like planets/habitats...
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Nope, GP had it right. He's saying his model is wrong.
Re:Then he's doing it wrong. (Score:4, Insightful)
It is what he's saying. If you've got a "model" then you should be able to make predictions from it and test those predictions. In this case, his model predicted "There's no way Earth could happen based on this." so we know his model is off. That can be a good thing, as it can give us more specific insights as to where our understanding of physics has its gaps, if his model is true to our laws of physics.
Because there's not just Earth. Mars isn't "far off" from being habitable, and neither is Jupiter's Enchilada Stand. 3 spots in a single, relatively small solar system that have the geological potential to bear life are showing 3 massive errors in our understanding of the universe's development.
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Venus is really not that far off either. It just needed a slightly different orbit. (And a molten core, I guess.)
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Venus is really not that far off either. It just needed a slightly different orbit. (And a molten core, I guess.)
And a Moon, and an Ocean.
Oceans could come from comet impacts, and a moon can be captured. I'm not an astrophysicist, but these two things don't seem outside the realm of possibility.
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Venus is really not that far off either. It just needed a slightly different orbit. (And a molten core, I guess.)
And a Moon, and an Ocean.
Does it need a Moon? Ok, tides but is that a deal breaker?
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Why do you need a moon for life to exist? Because otherwise women can't menstruate?
Sure, the moon has some useful effects for life (tides,...), but it doesn't really seem to be a requirement.
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Hm. the "terraforming venus" wiki entry said that Venus lacked a magnetic field like Mars. I made the leap that Venus must have a solid core, like Mars. My mistake.
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Venus may well have had life early in its history. We'll probably never know. We do know that there is a good chance that in a couple of billion years, Earth will be similar to Venus. The Sun keeps getting hotter, eventually (0.5-1 billion years according to current understanding) the oceans boil causing a runaway greenhouse affect, plate tectonics stop as they seem to depend on oceans, CO2 increases in a runaway manner and the Earth becomes Venus like.
We have at least 3 planets in our solar system that wer
Re:Then he's doing it wrong. (Score:4, Funny)
He's from the Climatology School of Modeling.
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And you're evidently from the Idiot School of Life
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The climatological models are actually rather accurate. I know, I know - that's not to be posted on Slashdot, but I thought I'd at least attempt to counter your little dig.
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"Because there's not just Earth. Mars isn't "far off" from being habitable, and neither is Jupiter's Enchilada Stand."
I for one truly believe there is life at Jupiter's Enchilada Stand, and plan to visit it someday for the #3 platter too.
captcha - biology
HAH!
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I've always argued the point with my peers about how unique Earth is. Yeah, there are a few
possibilities in our own system, but Carl Sagan (as much as I loved what he did for science)
err'd in his assessment that everything was a linear problem with 1 variable (you know the speal,
a billion galaxies, 1 percent have this; and of those 1% have that, etc. and so on till he arrived
at still a large number of "earth-like" planets that life could have evolved. Problem with that
reasoning is that from one step to th
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Re:Then he's doing it wrong. (Score:5, Interesting)
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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That's why I'm a bit curious about what he considers an "Earth". There's only one Earth in our solar system once you take into account the large moon, magnetic field, liquid water on the surface, plate tectonics, air pressure, and factors like that. But there's several places that could plausibly support life, or once could have. Things mentioned in the article such as being in a larger galaxy, or being bigger than Earth, or older that Earth* don't really seem to preclude a planet from being an "Earth" t
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"The thing about such models is that they're mainly useful in generating research questions than making predictions. "
+1 insightful, I'd say.
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That's not what he's saying. He says that earths are statistically rare.
And how can he possibly know that given the tiny sample size of solar systems we have seen so far compared to the number in the universe? Suppose the chance of an Earth-like world forming is one in a billion. Given the number of solar systems we have studied so far it would be entirely possible that we had not seen one so far and yet with 400 billion stars there would be 400 "Earths" in the Milky-way alone let alone in the billions of galaxies in the universe.
Extrapolating to a universe of billions of g
Re:Then he's doing it wrong. (Score:5, Insightful)
That's not what he's saying. He says that earths are statistically rare.
And how can he possibly know that given the tiny sample size of solar systems we have seen so far compared to the number in the universe? Suppose the chance of an Earth-like world forming is one in a billion. Given the number of solar systems we have studied so far it would be entirely possible that we had not seen one so far and yet with 400 billion stars there would be 400 "Earths" in the Milky-way alone let alone in the billions of galaxies in the universe. Extrapolating to a universe of billions of galaxies each with hundreds of billions of stars using a sample size of what, a few thousand?, ten thousand?, is statistically daft...and having a model which agrees with your statistically insignificant sample does not make it any better.
It seems worse than that to me. He isn't just using a small sample size, he is using a sample that is skewed toward large planets that are close to their parent star. How many exo-Plutos have we found? How about exo-Mercurys? I don't think we have even found a planet as small as earth yet, but I could be wrong on that. When the reports of exo-Earths have come out they have been larger than our Earth, but they call them an exo-Earth because it might be in the Goldilocks zone.
Car analogies work so well, lets use one here. We will make a model that recreates all the cars on the road. But we will only input the semi-trucks and tour buses. I bet the model will say that sports cars are highly unlikely. I think the term is GIGO, Garbage In - Garbage Out.
Re:Then he's doing it wrong. (Score:5, Interesting)
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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If I recall correctly, we don't yet have the capability to detect Earth sized planets.
That's not true. You can walk outside any morning right now and detect Venus yourself.
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Strange...I just looked out the window and detected an Earth-sized planet. I couldn't see all of it, though, but I'm pretty sure about the size.
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I haven't read the article yet, so if I were wise I would keep my mouth shut. But...
I think part of the problem has been that too many giant planets have been found in orbits close to their star. A Jovian or super-Jovian class planet that close causes some kind of instability over the eons to the orbits of smaller planets in the habitable zone, or so I've heard. (It has also been proposed that the migration of a Jovian-class planet from its far-out position where it formed to a near-star orbit would wrea
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Inferring things about populations from tiny samples is kind of how statistics works. The problem here is that statistics assumes your sample is random, and our sample of exoplanets is definitely biased.
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Statistics works by inferring things about populations by using a random sample that accurately resembles the population and has the appropriate size. I can definitely say that using a bunch of super Jupiters and super Earths that orbit very closely to their stars is not an accurate sample representation. As to the sample size I no longer have the math skills to work that out as it's been over 25 years since I've taken those courses in university. However I have a feeling that approximately 2,000 planets
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Yes, a non-random sample is called a biased sample. Variance decreases your confidence in your answer. Bias makes you get the wrong answer, confidently.
The size of the population actually has nothing to do with the size of your required sample, although the complexity of the things you're trying to explain can. You can make valid statistical inferences with only two samples, although you'll have extremely low confidence. Our current sample of thousands of exoplanets would be more than good enough to mak
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Inferring things about populations from tiny samples is kind of how statistics works.
Yes but you are limited in what you can infer by the ratio of your sample size to the entire population even if you have a random sample to start with. If you ask one US voter which presidential candidate they are going to vote for and they say X you cannot then infer that X will win the election because there are a few hundred million more voters out there. The best you can do with such tiny statistics is set a limit on the number of Earths out there and it will not be a very good one!
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Yeah, or he's working with an incredibly incomplete data set, which his model is based on. Considering that we know roughly the square root of jack shit about even our own corner of the galaxy, much less the rest of the universe, I think I know which side I'd put my money on.
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He doesn't even say that, according to the article. He says Earth may be a "mild statistical anomaly." We were pretty sure about that just from the composition of our own solar system.
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It's not just the composition of our own solar system, it's also the improbable orbital gymnastics required for the Earth to end up with an orbiting moon with about 1/8th of its mass (well 0.012300 times as much). How important is that? I don't think anybody knows. But the capture event itself did a lot of rearranging of the material distribution leading to the Pacific Ocean and an unreasonably heavy crust.
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That's not what he's saying. He says that earths are statistically rare. That doesn't make any predictions on the amount of life in the universe that might exist on not-earth like planets/habitats...
From HHGTTG: The Universe [wikia.com]
Population
None. Although you might see people from time to time, they are most likely products of your imagination. Simple mathematics tells us that the population of the Universe must be zero. Why? Well given that the volume of the universe is infinite there must be an infinite number of worlds. But not all of them are populated; therefore only a finite number are. Any finite number divided by infinity is as close to zero as makes no odds, therefore we can round the average population of the Universe to zero, and so the total population must be zero.
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You shouldn't necessarily drink a quart of water where the percentage of arsenic has been rounded down to zero.
All due respects to Douglas Adams, but you do know that he was being rather silly a lot of the time. He even knew this, rumor has it.
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He says that earths are statistically rare.
If they are not impossible, merely highly improbable, then by the Law of Big Numbers their existence is inevitable.
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