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Planets In The Habitable Zone
mistah_monkey writes: "The BBC reports that an international team of scientists have identified some planets in what they call the habitable zone. Apparently, the planets may be as big as Jupiter, but exist in a region surrounding the stars they orbit in which water can exist as a liquid, which is good news for those of us who believe that little green men might actually be out there somewhere."
You mean, like Europa and Titan, moons of gas giants in our own solar system that are capable of supporting life?
And you mean "tides" as opposed to "tidal wasves(sp?)", correct? Tidal forces on a moon of a gas giant would be very impressive, to say the least.
"Don't mind me cutting myself on Occam's Razor"
Okay, not war. How 'bout overconsumption? It has certainly ended numerous civilizations here on Earth, and no one is even sure if the six billion we hope to support right now is a sustainable population long-term.
And the thing that makes it a much better curtain-closer than war is that we will sit around and watch it happen and be unwilling or unable to change our way of life enough to stop it. Witness global warming.
"You can't get something for nothing." - my grandfather, on the stock market and Reaganomics.
Thanks for the link. Though I should point out that the authors note that tidal forces may sustain a smaller moon's geological activity for a sufficient period of time.
Which makes me think. If there were a habitable moon due to some lucky combination of size, parent's orbit, magnetosphere, tides, etc. would its inhabitants sit around saying: it's so unlikely that these factors combined to make our world habitable, what are the chances that a planet in the habitable zone could support life? All the while not knowing that a *different* set of lucky circumstances had done so?
My point being that even if it takes an intricate balance of physical factors to make life possible, the sheer number and variety of such combinations makes many such intricate balances possible. Just as there are many different intricate ecologies on Earth, and many of the creatures in any one habitat would go extinct from the slightest change, and yet all of these intricate ecologies support life in some form.
"You can't get something for nothing." - my grandfather, on the stock market and Reaganomics.
I think Monty Python refers to the speed of the Earth's surface at the Equator - but in knots (nautical miles an hour) not statute miles per hour. The Equator is roughly 22,400 nautical miles all around. Divide that by 24, and you get a speed of 933 knots at the equator. The earth's orbital speed would be:
2 * 150,000,000 * pi = 942,477,810km
942,477,810 / 8760 = 107,588 km/h
In miles per hour this is:
107,588 / 1.6 = 67,242 mph - just a touch faster than 900 mph!
270,000 / 67,242 = a sedate 4 times faster than the Earth.
Oolite: Elite-like game. For Mac, Linux and Windows
What the Hell is this "Zone"???? A region around 1 AU? NONSENSE! Earth is probably more an lucky aberration than a rule of the thumb. It is probable that it is extraordinary that Earth formed at such distance of the Sun with all the parameters to keep a large amount of liquid water on it. Look at the Moon for an example of what I'm saying... In fact the "habitable zone" should be generally be a bit more far away than Earth. I mean the highest probability zone. Because all this is a probability function based on the theories of planetary formation. It is considered that planets are formed from a planetary nebula. And that the "habitable zone" will be a region where water will have the chance to condensate AND later to keep its liquid form.
In general, in the case of a sun-like star this would look like a probability function that starts at zero from the center of the system, keeps zero up to regions between Venus and Earth, sharply rises between Earth and the asteroid belt, and slowly lowers up to a region beyond Jupiter. We know that there were oceans in Mars. We know that the Moon shows Earth as being on the EDGE of this zone. We know that there is the high chances for Europe to have an inner ocean. And we have a hot Io showing that tidal phenomena may trick the whole game of temperature distributions. So if one searches for "habitable zones", then he should search for a region much larger then the Solar System and surely not at 1 AU. Mars lost its water for some damn cosmical impact that send into bubbling to Cosmos. And there are indications that, even now, water makes a good part of the landscape.
Besides I don't see the good point to remark huge planets in highly elliptic orbits. Because they are inside the 1 AU? And what about the escape velocities produced by these orbits? We surely will not find Extra-Jupitereans. We can only rely on the possible sattelites around these planets. And these planets will have very thiny chances of possessing big sattelites with enough conditions for life. Because they need to be big and fat. Or else they will be cooked like the Moon.
Besides what about the chance of Jupiters at Jupiter's distance but with Mars-sized satellited. It is quite possible. And we know that the tidal game may trick the production of enough heat to give habitable conditions to these planets. While these would be exceptions, they are not far from the conditions we even see on Jupiter. At least everyone says there is a good chance to find Life in Europe. There is no arguments to dismiss this fact, on the contrary. And sincerly Life doesn't exactly need the surface of a planet to live and survive. So "underground" habitable zones may extend even further...
grumble.. I should remember that the circumference of a circle is not pi*r^2, but 2*pi*r. duh. I was only off a factor 12 billion.. *sigh*
//rdj
No one can understand the truth until he drinks of coffee's frothy goodness.
--Sheikh Abd-Al-Kadir, 1587
This hypothetical civilization colonizes the galaxy in a few million years?
And in all that time, this race has no wars, no economic hard times, no diseases? That could slow them down. It could be that it is culturally a very difficult thing to do, to colonize other planets, light-years away. Given the cultural drift that can occur in two societies that are isolated and unable to communicate, the likelyhood that wars would erupt seems almost a guarantee.
And, even if it IS NOT possible to travel faster than the speed of light, what if it is not technically feasible to colonize another world at all? I mean, we like to draw parallels with sailing the Santa Maria across the Pacific, but it's not quite that simple. It takes a huge amount of resources just to get a paperweight into orbit. Now, how about putting a ship large enough to be home to 1000 or more people for generations, into space, and across the gulf of light years - barring again, disease, cultural instabilities, technical difficulties, etc. Yes, we all want to believe that these problems can be surmounted by a sufficiently advanced civilization - and I'm not saying that they can't. We don't know that. But what if, just what if, that IS the case, that as far as technology goes, we've gone just about as far as we can? What if fusion power is not feasible? What if 1000 people on a generation ship kill eachother? What if life on a generation ship is not sustainable, or requires a much larger biosphere than can be constructed without threatening the economy of the civilization that is building it? What if, 50 years into the journey, an airlock seal blows because a greedy contractor cut corners? There are a lot more reasons why this wont work than simply a civilization blows itself up with atom bombs. And even if it can be made to work, what if it's just a lot harder than we think it is. In that case, the rate of colonization may be much, much, slower than this theory states.
These estimates, that the whole galaxy ought to be colonized by now, in my opinion, are far too optimistic. It has been theorized, how it could be done, but was the full economic impact on the civilization measured? Were ships designed beyond the basic features and principals? This ought to be done with current human technology, to see if it can be done at all. We're not even sure if we can technically put a human on Mars and bring them back - there are many unanswered questions, such as, radiation, human endurance, margin for error, the martian environment (dust, it seems, will be a very seriously major problem, as yet, unaddressed).
These are my friends, See how they glisten. See this one shine, how he smiles in the light.
Yeah, nobody's asked about something that's pretty unique to Earth, namely: "has to get whacked by a Mars-sized impactor real early in its development".
Any ideas if that impactor was ice-rich and if any water vapor from impact could have hung around as the resulting mess cooled (and produced the Moon)?
Seems to me the "big whack" comes in handy for:
The moon - nice tidal energy pumps to stir the oceans
The water (maybe, as I'm wild-assed-guessing in my first paragraph)
The seasons - the 23-degree axial tilt that lets the sun drive energy back and forth across the surface of the planet I'll accept that big whacks are pretty common (Uranus' axial tilt, etc.)
This doesn't cut down on the number of habitable planets from the point of view of a colonist from a technologically-advanced civilization.
But if it's a major factor (or an essential), it may cut down significantly (like, say, eliminate 2/3 of the planets - asusming Earth, Whatever-Got-Mushed-And-Made-The-Asteroids, and Uranus - 3 of 9 whacked planets) on the number of habitable worlds on which life actually evolves.
(Yeah, the only way to find out is to do lots more planet-hunting, huge-ass interferometry, attempt to get spectra and what-not... the nice thing is that younger /. readers may actually see the results of the research in their lifetimes...)
not only is tidal locking a serious problem, but as others pointed out, variations in temperature due to varying distance to the sun, or shading by the main planet would also have some harsh effects.
Also, IIRC, Jupiter has some pretty intense radiation belts. Intense enough, that they pose a challenge to probes navigating the moons. IIRC, Gallileo had some hard resets when it passed through them. Now that doesn't mean that life cant exist, but all of these factors together make it unlikely to be stable - in other words, able to undergo speciation, let alone, develop into something that can post on slashdot.
These are my friends, See how they glisten. See this one shine, how he smiles in the light.
the laws of probability say there SHOULD be other forms of self-replicating material (aka simple life) out there. have we heard anything to suggest there isn't or can't?
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These jovian type planets in the habitable zone of their stars may have tidally-locked moons that are dense enough to harbour life. In our own solar-system, Jupiter's moon Europa is suspected of having a liquid water layer under an ice crust, maintained in that state by a constantly deforming rocky core.
Larger mars-size satelites (or even larger earth- or venus-sized ones) could be orbiting these planets at distances that lock them tidally, or further out, giving them an even more tectonically active crust than we have as a result of our moon.
In any case, such a world (they wouldn't technically be planets) would have all the same ingredients for life that we do, just in varying proportions, possibly leading to life, not as we know it, but at least recognizable as such by us.
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The seasons don't do anything to promote life. By far the greatest concentrations of life in the tropics; both on land and in the sea, and they don't have discernable seasons. In fact, seasons are a hurdle to life: places with the largest seasonal differences (like the arctic) have the least biodiversity.
Exactly. Drake had no illusions that the equation could answer the question. It was just meant to clarify the question, which it does quite well.
Any "solutions" I've seen of the equation were plainly tentative -- "If I'm right about these values, then this is the result." Sloppy thinkers/writers might not be clear about that, and -- at least as likely -- sloppy readers might miss the qualifiers. But that's not a problem with the equation itself.
Well taking a good look at some of these orbits I would doubt we could find such repositories. zi mean the high elliptical ones. First we know that at 1 AU and less, Moon-sized moons would be virtually cooked by the star. And every planet with a wrong wobble would get into the same fate... Then we should take into account the huge tidal forces produced by these orbits. So probably most moons would look more as hot melted cheese. And then we should think if there are such moons at all, as the escape velocities would be tremendously high for large moons.
Considering the number of such elliptical planets, chances are much lower than one should expect...
Ennui
Ennui
"I walk in the air, between the rain, through myself an
I love it when the Drake equation is invoked as a way to calculate a meaningful result with some relavance to human or alien civilization.
The Drake equation is calcualted by multiplying seven terms together. 3 of those may be obtained from reasonable sources in astrophysics and planetary formation research (albeit they are continually changing as we learn more!). The other 5 terms are picked essentially at random, and therefore have no meaningful value.
The only thing the Drake equation is good for is exploring the relative impact that manipulating various terms may have on hypothetical contact. Due to 5/7 of the numbers being completely arbitrary, it has no value beyond that limited application.
Use of the Drake equation is a great example of "subjective" science. Adding an additional term defining the probabability of the society creating Twinkie's and eating themselves to death in a cream filled orgy before transmitting would have no detrimental impact on the reliability of the answer.
I've heard that the moons of such planets are the more likely repositories of life. The moons would have liquid water, and a gas giant might be a source of additional heat if they emit more heat than they take in like Jupiter does in this solar system. I do wonder about sunlight, though, with a gas giant providing eclipses.
Logic ... merely enables one to be wrong with authority. -- Doctor Who
Hah! Got me there. That's what I get for posting after 4 hours sleep. Hit submit instead of preview, too. :)
Even the "example" you quote, that of "how the Universe came into existence," about which you say, "the fact of the matter is that we know nothing..." is a poor one. Like all scientists, astrophysicists have formulated a theory (namely, inflationary Big Bang) which explains certain observational facts, makes certain predictions, etc.; furthermore (and quite significantly), it is generic in the sense that the results it predicts are not sensitive to a large number of parameters. I could yak on about this ad nauseum, but briefly, observational corroboration includes the existence of a Hubble flow (velocity is proportional to distance), the existence AND detailed properties of the cosmic microwave background (to wit, its isotropy to one part in 10 ^ 5 or so, the fact that it has the spectrum of a perfect 2.7 K blackbody, and the manner of the very small-scale anisotropies), and the ratio of light element abundances. Show me another theory that predicts all these things, in a natural way (ie, without invoking 27 free parameters to tune as you wish), and I'll listen to you; but hell, do that and you've probably won a Nobel anyway, so why bother with me? Furthermore, the physics of the Universe before nonlinearity should actually be very well described by "normal" physics -- and if it's not, that's a fundamental problem, independent of the application; the kicker, though, is that we have no solid evidence that the physics here doesn't work.
To sum up, my NSHO is that you are a) unclear about what exactly astrophysics entails, is, and relates to, and b) are unable to back up your broad claims of illegitimacy with fact. Your one anecdotal evidence of the evils of astrophysics, regarding the greenhouse effect on Venus, is so incidental as to be laughable: I know jack about the atmosphere of Venus, or about greenhouse gases in general, or really about planetary science in general, but then again I don't really have to; the vast majority of topics in astrophysics have absolutely zero to do with it. My totally biased opinion is that Carl Sagan probably has given more thought to this than I have, or than you have, or even (perish the thought) than Gunnar Heinsohn, whoever the hell he is. Your argument is like suggesting that if a chemist can't predict the bonding properties of C60, all of chemistry is flawed.
Have a nice day. :-)
Density does effect gravity. This is because gravity is inversly proportional to the square of the distance between the two masses. While this relationship is difficult to model for a vastly large body, like th Earth, you can simplify it by thinking of the distance being to the center of the Earth. Mass closer will exhert more gravity, mass farth will exhert less, but it mostly works out. If you strech the mass of the Earth over 10000 times the volume (no where near the size of a nebula, BTW), you would get 1/(10000)^2/3 ~= 1/464 times the gravity (the cube root is because it is square to the distance, which is found by the cube root of the volume).
Of course, this isn't to say that density is the actual important factor. It is of course, Gravity. A 10000 times larger body with 464 times more mass would have the same gravity and could sustain an atmosphere like earths.
-no broken link
It's an antiquated expression, whereas 'sublimes' is more accurate and more acceptable in modern circles. 'Camphoring' is more likely from Middle English than technical. It uses a substance to describe a process, similar to the way 'ice' implies the substance 'water,' but could describe other substances solidifying.
The important thing is that a planet must have a good degree of pressure. On tall mountains, you can boil water away in a paper cup, but on a depressurized surface like Mars, you couldn't get water into liquid form to begin with, unless it is pressurized. On the moon, they're not about to look for liquid water, but it is believed that it can exist in solid form (ice) located in shadowed wells.
Sure, we can discern some of the many differences between atmospheric density (pressure) and mean density of a planet's various layers... There can be/is great variety in each planet's frame. If you vaporize the metalic core, or even substitute it with an equivalent mass of atmospheric gases, what have you got? You'd have less than 1G coming from the earth-equivalent mass (Newton's Law of Gravity says the increased distance, *squared*, would proportionally reduce the gravitational force.)
Heating and cooling poses interesting questions... A solid mass stabilizes a lot of the mean temperature. Would the gases quickly take off, cooling the nebula in disappation? Would they heat like a greenhouse, and begin radiating like a gas-giant? Probably both, but in what portions? Actually, a scientist friend of mine points out that space's so-called vacuum is actually rather hot to the gases travelling through it... the free-flying particles have neither the shade nor the dense gravity to slow their velocity. Of course, a solid mass in shade might not notice, unless it were small enough for the exchange with light gas to transfer comparable tempurature/mass.
It takes a lot of gravity to make a gas giant. If you could stand on the surface of the Sun and sense the pull of distant planets, Jupiter has more than 11 times the pull of Earth, despite having four times its distance.
1. Starting an uncontrolled nuclear chain reaction requires lower tolerances than controlling a chain reaction that is just subcritical. This means that fusion bombs are technologically simpler than nuclear rockets or fusion power plants.
2. Elliptical orbits with periapsis belows a planet's surface are lower energy than circular orbits at the ellipse apogee. This means that ICBMs are technologically simpler than orbital rockets.
Science fantasy authors love to write stories about "silicon-based life", but anyone with sufficient training in biochemistry can tell you silicon won't work as a basis for organic life.
And if you're going to consider even more exotic ideas ("photonic life" a la Star Trek, or neutronium life), you might as well be discussing ghosts and gremlins. They're just as plausible.
The main candidates out there are carbon/water life vaguely similar to stuff on Earth, and possibly machine intelligence (previously built by carbon/water life).
The inhabitants would have significant advantages in the world of e-commerce. They are already running on "internet time".
-no broken link
I suppose here is as good a place as any to wrte this. I have become quite fed-up with this notion that war will somehow lead to the end of our species. Really, I find it quite ridiculous.
War is a rotten thing with a lot of bad effects--it's very rarely worth the expense. But there's always at least one winner left at the end. What about nuclear war, in which two sides could conceivably destroy each other utterly? It won't happen. Nuclear weapons will not be used on a large-scale basis until mankind is spread across several planets. And when that happens nuking one planet will do nothing at all to that other planet.
Nukes may be used on a small scale here, but I doubt it. Too much stigma in every nation. Pity, too--some of the clean weapons are, quite frankly, amazing. FAEs are still cheaper, though--and they don't give the nuts as much of a scare.
Don't just absorb the environmentalist line, think about it. They're only about half right.
Mare Infinitus. Endymion, damnit.
Wait, that's four. Damnit, now it's eleven.
--
If density were indeed unrelated to atmospheric pressure, why doesn't Ceres have an atmosphere? Density, mass, and temperature are three, and not the only three, variables that influence such a thing. (A superdense asteroid the size of Ceres could hold a dense but shallow atmosphere.) Wouldn't Venus' atmosphere solidify at an increased distance? Would Titan's boil away if too close?
If Earth had its present density, but size were increased to that of Jupiter, it would lose the low gravitational mass I speak of.
Picked apart like hair-splitting equations, these relationships are indeed incomplete. But taken together, like the balance of relationships as which they were presented, they illustrate a useful component of the facts we'd need to address in colonizing other worlds.
And 'chaos' is not from a cult or religion, but from ancient greece, the birthplace of western civilization. Granted, many of those guys believed that life came from the chaos of fire, and to fire it would return. But if relating the word chaos to fractals or dynamic energy wigs you out, then you may find difficulty with certain fields of modern mathematics. (I'd also suggest avoiding 'Jurassic Park.') ;-)
Chris Kuivenhoven is a thief, beware
Hmm.... so the maximum distance that a planet could orbit our Sun and be spontaneously habitable (i.e. without terraforming) is about
1.25 AU.
At this distance a Terrestrial planet with the standard inventory of CO2 and H2O would have started off some 4.5 billion years ago with
a surface temperature and pressure very similar to modern Mars. As the sun warmed, the planet would slowly warm too. After about 1.5 billion
years, the planet would thaw enough for liquid water to be stable at the equator, and the process of conversion of CO2 to carbonate rock would
begin and the extensive CO2 pole caps would begin to disappear. Once consumed, their depressing effect on temperature (caused by the
reflection of sunlight back into space) would be removed and the planet could warm up appreciably. At the present day, such a planet would have
Earth-like temperatures but would need a large proportion (15%) of CO2 in the atmosphere to acheive this. 15% CO2 is poisonous to higher life
forms, but extremophiles can survive and if this was the planet's atmosphere, then life could well evoilve to tolerate it.
There's no reason why life couldn't evolve on a colder planet, further from the Sun. But it would be forever restricted to underground habitats
where volcanic activity warmed the ground. In nature, this life would resemble extremophile bacteria and algae on Earth, which appears to have
been the first form of Terrestrial life from which everything else evolved.
My (very approximate) calculations show that the planet's travelling at about 270,000 miles per hour, 300 times faster than the earth, if my Monty Python is correct.
MY calculations are:
2*6,000,000*PI = 38,000,000 kilometers
38,000,000/72 = 530,000 kph
530,000/2 = 270,000 mph
270,000/900 = 300 times faster than Earth
"The question of whether a computer can think is no more interesting than that of whether a submarine can swim" -EWD
You're thinking of Hal Clement's Mission of Gravity, but you seem to have gotten a few details mixed up with Robert L. Forward's Dragon's Egg (Mesklin in Mission of Gravity was a super-Jovian planet which rotated so fast that it was extremely flattened at the poles; the setting of Dragon's Egg was a neutron star).
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/. If the government wants us to respect the law, it should set a better example.
ObHakorz comment:
A firewall can not protect you from yourself. Turn off what you do not need. Do not use the firewall to do your work.
The great way to eliminate over-consumption is to get rid of subsidies. In a healthy market over-consumption leads to increased prices leads to decreased consumption. those societies which were destroyed by over-consumption generally had no check on the actions of their members, like money, or had an artificially-supported market somewhere. Bad bad bad...
>Earth is the most dense planet of our system.
This is not correct. Mercury is the most dense planet in our solar system. The Earth is made up largely of rock which is not that dense when compaired to the inner planets which have more nickel and iron. Go find a good solar astronomy class before try to lecture on the subject next time.
www.starstuff.org
"I'm just here to regulate funkyness." - James Gandolfini, as Winston in The Mexican
I finally got around to renting M2M last night - god what a horrible movie. "The Face" should have been "the Scarface" and it should have been made out of 100% pure Columbian white. Inside they should have found a bunch of Cuban gangsters, and maybe a high-school psychokineticist, instead of Bambi-the-space-alien.
A quick refresher of the chemistry of water, CO2, and life:
Water is an excelent solvent for polar (ionic) compounds like salt. CO2 is an excellent solvent for light organic compounds. Life consists of parcels (cells, globules) of complex chemistry, packaged in a lipid (fatty acid) membrane.
If water and liquid CO2 co-exist, they form small globules of one liquid in the other. At the interface, both polar and non-polar chemistry are possible. Lipids naturally line up at the boundary and form sheets that seal in the globules. Perhaps this is the first, crucial step towards the origin
of cellular life.
Maybe self-replicating chemicals already existed, but the packaging into cells was the vital step towards life as we know it. Perhaps conditions on the early Earth were cold enough for liquid CO2 to exist in some regions, and permit life to begin in this way? What a balance! Too cold and the water freezes. Too warm and the CO2 boils, and the greenhouse effect amplifies any change in insolation making the balance razor sharp.
If life required such a careful balance of temperatures to begin, then perhaps the habitable zone is much, much narrower than most people
imagine?
But the current laws of physics only apply until they are disproved or superseded. There are so many things we don't know (matter as a wave and a particle is something that hasn't been figured out yet) that to say that the physical laws currently held to be true are the be all and end all of science.
Still, the best reason to look for planets like that is they might be good candidates for a new home when we destroy/overpopulate/get-bored-with/quarantine/etc . earth.
And it evidently uses non-standard rules for addition, too....
/.
/. If the government wants us to respect the law, it should set a better example.
So let's go back to the notion that we're not talking about extraordinary life, thriving under pressure. Let's talk worlds we can personally colonize. We really aught to be seeking small planets like ourown, but dense ones:
Earth is the most dense planet of our system. Just divide Mass by Volume, and the greatest mean density is our own. Saturn has hte least, which may account for its lovely rings. But there are many fine balancing points working in Earth's favor:
- High Density==needed pressure for liquid water.
- Small Size==low gravitational mass, ==fewer sheering stresses fighting life's 'order.'
- Proximity to Sun==dynamic energy ('chaos') for creating (mixing) and sustaining (maintaining) life.
- Distance from the Sun==cooler order to prevent life from burning away in excessive energy.
So earth is unique to our system in being a light-weigth pressure cooker for life. We actually have a better chance outside our own solar system, where greater planetary densities exist, if getting there can be trivialized. Then again, the technology to make insterstellar travel trivial would likely make terraforming even more trivial.Furthermore, even if it could, its body would surely explode due to the low atmospheric pressure. Or, perhaps the weight of the organism could not be suspended by the atmospheric pressure and it would crash to the center of the planet.
There is also the thin atmosphere. The planet is small enough, but its atmosphere is a tiny shell and hasd a relatively massive solid core. That leaves little room for life to develop.
I tell you, Earth is no more habitable to life than Mars is now ever since the Matrians turned their gas giant into a desolate rock!
Ever heard of spectroscopy?
Gas giant moons would quickly become tidally locked (facing one side to the planet), so the tidal bulges produced by the planet would stay put. The only ebb-and-flow would be from solar tides.
/.
/. If the government wants us to respect the law, it should set a better example.
When you do the math as I suggested:
Mercury = 5.4299e+12 kg per cubic km
Earth = 5.5206e+12 kg per cubic km
That's what empiral data is good for... finding facts for yourself instead of accepting a spoon-fed generalization.
Whoops, wrong paper. Sorry. Well, here are just the radial velocity curves.
If the scenario is only slightly comparable to our own solar system, those gas giants should have heaps of lil' moons orbiting them.
Although the oceans shouldn't be too big - just imagine the tidal wasves :-)
-- Truth suffers from too much analysis.
-Cyclopatra
"We can't all, and some of us don't." -- Eeyore
Enrico Fermi (created first controlled fission reaction, among other things) responded to a question like this by asking: if intelligent life exists beyond Earth, why don't we have any evidence of it yet?
.1 percent head start from the beginning of the universe, and they would have made it in plenty of time to colonize Earth before we started walking upright.
Even if you throw in very pessimistic estimates about how likely intelligent life is to evolve, and how slow and hard it is to colonize other worlds, and how few colonizable worlds there are, it is still hard to come up with numbers that don't make it likely that an intelligent species would colonize the entire galaxy within a few million years of gaining space travel.
Imagine a race on an Earth-like planet on the other side of the galaxy develops intelligence and space flight. In our case, this took 3.5 billion years after the oceans condensed, give or take a few hundred million. So in their case imagine it took the same time, but maybe their solar system formed a percent or so closer to the beginning of the universe, about a hundred million years.
Now imagine that our shared habitat is so rare, that planets like this can only be found at an average distance of 1,000 light years from each other (note that we've found 50 Jupiter-sized planets within 150 light years of us in only a decade of slow, crude searching). Imagine this race never figures out how to travel faster than light, and takes 1,000 years to make a hop to the next inhabited world. Imagine that successful colonies are rare and take time to develop, and so it takes 1,000 years on average before a colony launches its own colonization mission. Even at this slow pace, a million years is more than enough for a race to colonize every habitable planet in the galaxy, including ours, as the galaxy is only 100,000 light years in diameter.
So, this race would need less than a
So, where are they?
"You can't get something for nothing." - my grandfather, on the stock market and Reaganomics.
Your statement that nuclear war "won't happen" is faith-based, maybe -- certainly there's nothing objective to assure us that it won't happen. Ever notice the willingness of some people to kill themselves in suicide-bomb attacks? To me, the possibility of a "doomsday" response by the losing side in a major war is very real. YMMV -- but reality is independent of either of our beliefs, isn't it?
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Politics is about making compromises. Religion isn't. --Michael Horton
>The smallest of the three is an object called a "hot Jupiter" because it sits just six million kilometres from its parent star, HD179949 in the constellation Sagittarius.
>The planet, which has a mass that is 84% of our Jupiter, orbits the star in only three days.
hmm.. a 72 hour year?? wow.. not only is this thing hot.. it's quite fast at 4.3633 * 10^14 m/s.
(6M km radius, assuming perfectly circular orbit). Anyone have an idea what average earthspeed around the sun is?
//rdj
No one can understand the truth until he drinks of coffee's frothy goodness.
--Sheikh Abd-Al-Kadir, 1587