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Billions of Habitable Planets?
cbv writes: "MSNBC has an interesting article about new calculations by Charly Lineweaver and Daniel Grether, both of the University of New South Wales in Australia, which provides an interesting answer to the question on how many potentially habitable planets exist in our galaxy."
As the article says, Jupiter-like planets can act like a debris-magnet to protect Earth-like planets from comets, asteroids, and the various other junk floating around solar systems. Their immense gravity can either force and object out of the solar system entirely or force it to collide with the large gas giant. (An impact which would leave Earth near-barran for centuries is barely felt on Jupiter gas giant.)
The moons of the Jupiter-like planet offer another possibility for life. Like Europa, gravitational stresses from orbiting such a large planet can cause heat to warm up a normally frozen world. This heat might help melt ice into water (as is thought to be on Europa under the ice shell). And where there's water, life might not be far behind.
Now this isn't to say that life=intelligence. We might be talking about the ET equivalent of bacteria, here. Still, the discovery of ET-bacteria would be a huge matter.
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Manned interstellar spaceflight would require:
Some have observed that the level of committment this would require of humanity would be like nothing ever seen before, and which would require devotion that has historically only been commanded by religious quests.
Toronto-area transit rider? Rate your ride.
I don't know if there are any correlaries to this Fermi Paradox, but based solely on your post I think Fermi made waaaay too many assumptions. Lets see...
I could go on forever. I don't consider this a strong argument. I prefer the approach of statistics, even if it can yield no answers based our on current lack of information.
I've already posted a similar comment in this thread, but since I formulated it rather bad and not too many people seemed to notice I'll make another try. And this time I'll cut and paste from this site.
One of the problems that the Drake Equation produces is that if you take reasonable (some would say optimistic) numbers for everything up to the average duration of technological civilizations, then you are left with three possibilities:
1. If such civilizations last a long time, "They" should be _here_ (leading either the the Flying Saucer hypothesis---they are here and we are seeing them, or the Zoo Hypothesis---they are here and are hiding in obedience to the Prime Directive, which they observe with far greater fiqdelity than Captain Kirk could ever muster). -or-
2. If such civilizations last a long time, and "They" are not "here" then it becomes necessary to explain why each and every technological civilization has consistently chosen not to build starships. The first civilization to build starships would spread across the entire Galaxy on a timescale that is short relative to the age of the Galaxy. Perhaps they lose interest in space flight and building starships because they are spending all their time surfing the net. (Think about it---the whole point of space flight is the proposition that there are privileged spatial locations, and the whole point of the net is that physical location is more or less irrelevant.) -or-
3. Such civilizations do not last a long time, and blow themselves up or otherwise fall apart pretty quickly (... film at 11). Thus the Drake Equation produces what is called the Fermi Paradox (i.e., "Where are They?"), in that the implications of #3 and #2 are not terribly encouraging to some folks, but the two flavors of #1 are kinda hard to come to grips with.
An alternate version of 2 is that interstellar travel is far more difficult than we think it is. Right now, it doesn't seem much beyond the boundaries of current technology to launch "generation ships," which power systems. An
alternative is robot probes with artificial intelligence; these don't seem so difficult either. The Milky Way galaxy is well under 10^5 light years in diameter and over 10^9 years old, so even travel beginning fairly recently in Galactic history and proceeding well under the speed of light ought to have filled the Galaxy by now. (Travel very near the speed of light still seems very hard, but such high speed isn't necessary to fill the Galaxy with life.) The paradox, then, is that we don't observe evidence of anybody besides us.
"If you think education is expensive, try ignorance" - Derek Bok
Do we have all the facts to say for sure that the Moon had nothing to do with formation of life and maybe even of intelligent life on this planet? Our closest neighbour is only 300,000km away from us and it is also a HUGE satellite for our planet. It has a profound effect on this planet, an effect that Deimos and Phobos of Mars can only dream about. How about tides that Moon enforces on our largest pools of water? It is possible that life was created specifically because of these tides, in the puddles of water that were left behind a tide (well that's a theory anyway).
So, how many of those planets have comparable Moons around them?
You can't handle the truth.
No matter how badly we mistreat this world, it won't be worse than anything we find out there, unless one happens to have extremely Earth-like life on it already, the kind of place they find all the time on Star Trek, with lumpy-foreheaded humans and grass and spruce trees (foam boulders optional).
By "habitable" they mean planets like Mars and Venus. Places you can live on in extremely well made air-tight shelters, and maybe eventually terraform.
We could have a sustained nuclear war (presumably sustained from off-planet), stripping the planet of sophisticated lifeforms and blowing off half of its atmosphere, and it would still be a nicer place to live than anywhere else in our solar system or anything we're likely to find orbiting another star.
In terms of human habitability, we're taking pretty good care of this one. Wiping out the wilds is sad, but a choice of farms or forests is easy for hungry people. Where it appears unnecessary, done too casually for convenience rather than survival, that is just staying ahead of what the population growth will demand in a generation or two. The pollution looks bad, but it's a feature of short-lived transitional technology, and will tail off before intolerable damage is done.
On the whole, human effort is greatly increasing human habitability of Earth, not decreasing it. The pristine, wild world of a hundred centuries ago couldn't support half a billion humans, while today it supports well over 6 billion, and the way is being made for 10. Even one century ago, it probably couldn't have sustained half our current population. Things probably won't get tight here on Earth's surface until at least 100 billion, by which time we'll be seriously working on these other places to live. As it is, we haven't seriously dented the resources of our planet, just dug around a little at the choice bits on the surface.
Combine this discovery with technologies such as global computer networks, advanced robotics designed for many purposes, the ability to genetically engineer any kind of living creature and terraforming technology, and we'll be able to create entire ecosystems that produce some intended results. Call it a computer--or more accurately, a machine--the size of a planet, with its output being anything from mined materials to manufactured consumer and business products to medicines and chemicals that are hard or impossible to produce on Earth. Nobody said the atmosphere on those distant planets need to contain oxygen--they could be saturated mostly in carbon-dioxide so that genetically engineered plant life could thrive, making unbelievable things possible. Imagine... on a distant planet, where plants grow extremely fast, robots cut down millions of trees every day and ship them to Earth. No longer would it be necessary to kill trees on Earth for houses, furniture, or even paper! Materials could be mined from distant planets. Why use up our own oil, metals, minerals and whatnot, when we can mine and retreive it from another planet? Why pollute our own atmosphere to manufacture things if we can manufacture them on other planets and let those planets get polluted? If designed correctly, those planets won't even get polluted! But who cares if they do?! Garbage crisis? No problem! Put it on another planet. The beauty of it is that no human being would actually have to set foot there! The robots could fix each other when they break down, and could be remote controlled from Earth, just like the Mars lander. It would be very beneficial to all of mankind, and would open up unbelievable multitrillion dollar international businesses that deal in interplanetary sales and distribution.