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."

Comments

Did they remember to subtract 1?

[blair1q]

Because by the time we can find another one that is, this one won't be.

--Blair
"Keeping up with the Gbrtlrxzes."

you mean...

[youngerpants]

N = R* × fp × ne × fl × fi × fc × L

Where,

N = The number of communicative civilizations
The number of civilizations in the Milky Way Galaxy whose radio emissions are detectable.

R* = The rate of formation of suitable stars
The rate of formation of stars with a large enough "habitable zone" and long enough lifetime to be suitable for the development of intelligent life.

fp = The fraction of those stars with planets
The fraction of Sun-like stars with planets is currently unknown, but evidence indicates that planetary systems may be common for stars like the Sun. more info

ne = The number of "earths" per planetary system
All stars have a habitable zone where a planet would be able to maintain a temperature that would allow liquid water. A planet in the habitable zone could have the basic conditions for life as we know it. more info

fl = The fraction of those planets where life develops
Although a planet orbits in the habitable zone of a suitable star, other factors are necessary for life to arise. Thus, only a fraction of suitable planets will actually develop life.

fi = The fraction life sites where intelligence develops
Life on Earth began over 3.5 billion years ago. Intelligence took a long time to develop. On other life-bearing planets it may happen faster, it may take longer, or it may not develop at all. For more information, please visit Dr. William Calvin's "The Drake Equation's fi"

fc = The fraction of planets where technology develops
The fraction of planets with intelligent life that develop technological civilizations, i.e., technology that releases detectable signs of their existence into space.

L = The "Lifetime" of communicating civilizations
The length of time such civilizations release detectable signals into space.

Re:you mean...

[LordNimon]

For those who don't know, the above equation is known as the Drake Equation. What a lot of people don't realize is that the equation itself is more interesting than the answer, because no one can truly know what values to use for the seven unknowns. To quote the above link:

The real value of the Drake Equation is not in the answer itself, but the questions that are prompted when attempting to come up with an answer. Obviously there is a tremendous amount of guess work involved when filling in the variables. As we learn more from astronomy, biology, and other sciences, we'll be able to better estimate the answers to the above questions.

Re:you mean...

[Theodore Logan]

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.

Re:The BIG question

[Scaba]

I think only telelphone sanitizers, hairdressers and middle management will get to go, if I remember correctly.

more than half

[Paradise Pete]

The most remarkable fact from the article:

We found that of all planets just reaching the dawn of their personal computing era, more than half of them have a whiney guy in glasses writing letters to magazines complaining about people not paying for his BASIC interpreter.

Jupiter-like planets offer 2 chances for life

[Jason Levine]

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.

Re:The BIG question

[s20451]

Manned interstellar spaceflight would require:

• A multi-trillion-dollar committment from the industrialized nations, complete with the political support for a project that could take centuries to implement
• Propulsion technologies (large-scale solar sails, nuclear / anti-matter propulsion, etc.) and life support technologies that are currently only imagined
• Orbital construction of a 10-100 thousand ton spacecraft - including shielding, centrifugal gravity, recycling, fuel ... possibly more than one spacecraft, for the sake of redundancy
• Extensive space infrastructure -- you might want to construct the craft from lunar materials, since it would be easier to launch
• A few dozen (or more) highly skilled, highly motivated people to operate the spacecraft, are willing to assume the risks of a 20-50 year journey in an untested spacecraft, who would be able to work together in extremely difficult conditions over decades without killing each other, and who would be willing to never return to Earth (maybe even willing to die before seeing the destination, with only their children arriving)

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.

Safety and Security.

[Talinom]

I don't care how many worlds there are in the Galaxy. I'm NOT going to wear a red shirt when I beam down to one of them.

Cute, but false.

[Nindalf]

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.

Re:Metrics...

[FrankDrebin]

Can anyone tell me the difference between a 'metric buttload' and an 'Imperial buttload'? Thanks.

I believe the imperial buttload is based on the size of Hing Henry V's rear end. Quite large, it was.

While the metric buttload is smaller, it scales nicely. For example, there are 10 metric buttloads in a metric shitload.

QED

Short lived civilizations could be good, not bad

[FreeUser]

3. Such civilizations do not last a long time, and blow themselves up or otherwise fall apart pretty quickly

Or alternatively, civilizations progress at a geometric rate, transcending themselves in a few short generations, so that by the time intersteller travel becomes feasable they have lost interest and moved on to more compelling possibilities (perhaps departing this frame of reference entirely).

Once one hypothesizes a civilization significantly more advanced than our own it becomes difficult to even imagine the technologies they may have, much less what interests they would find compelling, or what goals they might set for themselves. For all we know they are all around us, unrecognized because they operate at levels as far beyond us as we are beyond the simple microbe.