Odds of Finding Alien Life: An Exploration

[Rocketjj]

What do you guys reckon to the odds of us finding alien life?

The fermi paradox:
'If there are all these billions of planets in the universe that are capable of supporting life, and millions of intelligent species out there, then how come none has visited earth?'

I reckon there exists intelligent life, but the universe is simply too large for anyone to travel the distances required to find other planets in distant galaxies. I do think we may find alien life on some planets within ~100 light years of Earth once we gain the technology to reach these exoplanets. I don't think these planets would be capable of harboring intelligent life, but maybe some lower life forms!

 

[Nabeshin]

Given our current understanding of the laws of physics, intergalactic travel is more or less impossible (read: impractical). Unless there is some way to circumvent the light speed barrier, then it seems very unlikely that intelligent species would ever reach out very far in the galaxy. The fact is, what kind of a society is going to finance a (presumably very costly) expedition the results of which will not be heard of for centuries? One can argue all day about how perhaps these aliens have longer lives and perhaps their society considers this a worthy investment, but the fact is there are many many many factors stacked up against the probability of anything resembling a galactic empire or even inter-stellar society.

 

[N721YG]

The Drake equation
http://en.wikipedia.org/wiki/Drake_equation
predicts the chance of intelligent life in the Milky Way at 2.31 times using current knowledge. Primitive life forms may be everywhere, including in our own solar system.

Just 100 years ago people would have said going to the moon would have been impossible so there is hope. We live in exponential times.

 

[Rocketjj]

I see, but shouldn't these primitive lifeforms have evolved ? They may have been around for billions of years. It took 4billion years here on Earth to get from bacteria to humans...maybe other planets are not capable of complex life forms? maybe due to fluctuations in temperature or lack of carbon

 

[LURCH]

Although intergalactic travel seems unlikely without speeds above c, interstellar travel is quite likely. This is a part of the Fermi paradox; if other intelligent life exists in this galaxy, why aren't they here? Given no lightspeed, and advances no quicker than our current pace, we will be all over this galaxy in less than 100,000 yrs.

If another civilization exists within this galaxy, it would have to be less than 1,000,000 yrs old, or they would have collonized Earth before we arose. This is a very narrow window, and makes it unlikely that such a civilization currently exists.

 

[Nabeshin]

Given no lightspeed, and advances no quicker than our current pace, we will be all over this galaxy in less than 100,000 yrs.

Will we really? Technologically, I certainly agree with you. Socially however, as I pointed out, do you really think we would fund such expeditions that we have no chance of hearing back from in our lifetimes? Are we going to spend trillions of dollars simply to send people out in space to never return?

The only way this seems possible is if every single social crisis on Earth is solved and there's literally nothing better to do.

 

[Rocketjj]

Thats a very interesting view LURCH, thanks for sharing.

 

[D H]

The Drake equation http://en.wikipedia.org/wiki/Drake_equation predicts the chance of intelligent life in the Milky Way at 2.31 times using current knowledge.

The Drake equation is not scientific. It is a kludge that incorporates time in only two places, the star formation rate and the lifetime of a civilization. It ignores the incredibly long time span between the formation of multicellular life and the formation of intelligent life, and the much , much longer span between the formation of primitive life and complex (but still monocellular) life. It ignores that stars themselves have a limited lifespan. It took 1/2 of our own sun's lifespan for communicative intelligent life to arise.

Although intergalactic travel seems unlikely without speeds above c, interstellar travel is quite likely. This is a part of the Fermi paradox; if other intelligent life exists in this galaxy, why aren't they here? Given no lightspeed, and advances no quicker than our current pace, we will be all over this galaxy in less than 100,000 yrs.

The Fermi paradox is one of the indicators that something is awry with the Drake equation (or with the very overoptimistic numbers typically used within it). That 2.31 extant communicative species in our galaxy means an untold number of failed communicative species in the past. One of them would have spread.

My personal opinion: The "pessimistic" interpretation of Drake's equation in the wiki article, 0.05 extant civilizations in our galaxy, is extremely optimistic.

 

[yenchin]

Space travel is not just about exploration though, it is essential for survival of any advanced species if they were to live pass the life time of their star. When the Sun goes into red giant stage, we had better have somewhere else to go by then (although one can just get into a space colony of some sort without traveling too far I supposed...)

 

[Ivan Seeking]

The fermi paradox:
'If there are all these billions of planets in the universe that are capable of supporting life, and millions of intelligent species out there, then how come none has visited earth?'

How do we know that none have? The assumption is a bit paradoxical given all of the ET claims.

A walk on the wild side
Journal of the British Interplanetary Society, Vol 58, pp. 43-50, 2005.
http://www.ufoskeptic.org/JBIS.pdf

 

[N721YG]

...we will be all over this galaxy in less than 100,000 yrs.

If another civilization exists within this galaxy, it would have to be less than 1,000,000 yrs old, or they would have collonized Earth before we arose...

Maybe Earth was colonized and that is where life came from. Any # of setbacks could have wiped out the history books.

I doubt if would take 100,000 years to travel the galaxy. Because of exponential growth of knowledge, it could increase millions of times in the next 100 years. Unfortunately I think the H-bomb, a meteor or over population will bring us down.

 

[Nabeshin]

Space travel is not just about exploration though, it is essential for survival of any advanced species if they were to live pass the life time of their star. When the Sun goes into red giant stage, we had better have somewhere else to go by then (although one can just get into a space colony of some sort without traveling too far I supposed...)

I have two issues with this explanation. First, if space travel is merely a means to the end of survival, only when the native stellar system becomes unstable is it necessary and therefore there is no reason to expand beyond a single solar system at a time. Second, assuming a relatively average star and if we take the evolution rate of life on Earth to be something as normal (a huge assumption), then the lifespan of these civilizations are on the order of 5 billion life years. This is way way way more than is predicted by even the most optimistic proponents of the drake equation.

 

[Nabeshin]

Maybe Earth was colonized and that is where life came from. Any # of setbacks could have wiped out the history books.

I doubt if would take 100,000 years to travel the galaxy. Because of exponential growth of knowledge, it could increase millions of times in the next 100 years. Unfortunately I think the H-bomb, a meteor or over population will bring us down.

We are assuming no way is found around the light barrier. No matter how much you know, if you can only move sub-c then you are intrinsically limited in your ability to colonize the galaxy.

 

[N721YG]

We are assuming no way is found around the light barrier. No matter how much you know, if you can only move sub-c then you are intrinsically limited in your ability to colonize the galaxy.

I am thinking we will find a way around the light speed barrier at some point but let's say we don't. If well into the future we saw a problem coming with the Earth's ability to support life we would have some options. Most would agree future technology would allow us to locate potential planets for us to move to. A 1G continuous acceleration rocket could take us from one edge of the Milky Way to the other in just 12 years travel time. Our likely destination would most likely be much less distance. Earth time may be many thousands of years but who cares if it is dying. It would be a one way trip to save the human race.

 

[Vanadium 50]

The Drake equation
http://en.wikipedia.org/wiki/Drake_equation
predicts the chance of intelligent life in the Milky Way at 2.31 times using current knowledge.

That number in Wikipedia is innumerate poppycock. You can't take a bunch of order of magnitude estimates, multiply them together and get a number with three significant figures.

 

[atyy]

http://books.google.com.sg/books?id=R7phyBbqZDoC

"... they had come from Mars, but to disguise themselves they spoke Hungarian."

 

[Denton]

A 1G continuous acceleration rocket could take us from one edge of the Milky Way to the other in just 12 years travel time. Our likely destination would most likely be much less distance. Earth time may be many thousands of years but who cares if it is dying. It would be a one way trip to save the human race.

Are you kidding me? The milky way is 100 000 light years in diameter.Anyway whos to say that life isn't common. We know it is possible, aka us. Another advanced life form out there mightve sent autonomous spacecraft all over the galaxy seeding life.

 

[Jack21222]

I've been a lurker here for a few weeks... but WOW, this thread prompted me to register. A lot of incorrect information here.

If another civilization exists within this galaxy, it would have to be less than 1,000,000 yrs old, or they would have collonized Earth before we arose. This is a very narrow window, and makes it unlikely that such a civilization currently exists.

This is pure conjecture, totally lacking in any grounding in reality. Why would they have "colonized Earth" before we arose? Why would they do such a thing? Do you mean to tell me a species is going to travel 1000, 5000, 10,000, or 50,000 light years across the galaxy to live on our modest planet? They're going to skip over every other planet between here and there? How do you know that Earth's climate is even hospitable to those civilizations? Perhaps nitrogen is toxic to them. Wouldn't it be easier to colonize a planet with little existing atmosphere, to have a clean slate for "building" the proper atmosphere for the species? Surely there is a planet closer than thousands of light years away.

In short, your prediction that any alien civilization would have colonized Earth by now if they are older than 1,000,000 years old is flat-out absurd.

The Drake equation
http://en.wikipedia.org/wiki/Drake_equation
predicts the chance of intelligent life in the Milky Way at 2.31 times using current knowledge. Primitive life forms may be everywhere, including in our own solar system.

Just 100 years ago people would have said going to the moon would have been impossible so there is hope. We live in exponential times.

This is complete nonsense. "Current knowledge" still puts big ranges on some of the variables in the Drake Equation, and some variables have to be based on pure conjecture. For example, there is no way to scientifically calculate how likely an alien civilization is to have the desire to communicate. There is also no way to calculate the average lifetime of a communicative civilization. The Drake Equation estimates a range between 1 (us,) and hundreds of thousands.

That number in Wikipedia is innumerate poppycock. You can't take a bunch of order of magnitude estimates, multiply them together and get a number with three significant figures.

Exactly.

A 1G continuous acceleration rocket could take us from one edge of the Milky Way to the other in just 12 years travel time.

In whose frame of reference? It would take a minimum of approximately 100,000 years, regardless of acceleration, to travel across the galaxy from the point of reference on Earth. By the time you reached your destination, Earth would have went around the sun about 100,000 times, that is to say.

Now, if you mean from the point of reference inside the accelerating rocket, I don't know the math of Einstein's relativity enough to calculate it.

 

[Mk]

If another civilization exists within this galaxy, it would have to be less than 1,000,000 yrs old, or they would have collonized Earth before we arose. This is a very narrow window, and makes it unlikely that such a civilization currently exists.

This is pure conjecture, totally lacking in any grounding in reality. Why would they have "colonized Earth" before we arose? Why would they do such a thing? Do you mean to tell me a species is going to travel 1000, 5000, 10,000, or 50,000 light years across the galaxy to live on our modest planet?

He's only assuming here that the Earth is a desirable place for life.

Given no lightspeed, and advances no quicker than our current pace, we will be all over this galaxy in less than 100,000 yrs.

Where'd you get a hundred thousand from?

 

[Mk]

Back to the Fermi paradox and the chatting about numbers of years and light years:

On Earth it seems like similar traditions and technologies were developed independently by humans at around the same time. Perhaps geography was limiting or helpful in different cases, but nonetheless, there seems to be a clear path of development. Why wouldn't life be the same way? After the star systems and planets were created, is there a clear path of development from:

nonlife conditions > conditions conducive to life > conditions supporting of living organisms

 

[N721YG]

I've been a lurker here for a few weeks... but WOW, this thread prompted me to register. A lot of incorrect information here.
...
In whose frame of reference? It would take a minimum of approximately 100,000 years, regardless of acceleration, to travel across the galaxy from the point of reference on Earth. By the time you reached your destination, Earth would have went around the sun about 100,000 times, that is to say.

Now, if you mean from the point of reference inside the accelerating rocket, I don't know the math of Einstein's relativity enough to calculate it.

I don't see so much bad information but a lot of opinions based on speculation. Speculation is all we have in some cases. However, we do understand length contraction, time dilation and SR well enough to come up with real #'s.

A rocket at 1G continuous acceleration will go 100,000 ly in just 12 years according to the clocks inside the rocket. Over 100,000 years will pass on the clocks on Earth. If you want to end up at your destination stopped and not a splat it does take longer. You do not need to know the math well enough to calculate all this because someone put into a calculator that folks like me can ever use.
http://www.cthreepo.com/cp_html/math1.htm

 

[D H]

If another civilization exists within this galaxy, it would have to be less than 1,000,000 yrs old, or they would have collonized Earth before we arose. This is a very narrow window, and makes it unlikely that such a civilization currently exists.

This is pure conjecture, totally lacking in any grounding in reality.

Of course it is. Any statement regarding alien life (intelligent or not), is pure conjecture. Saying that LURCH's statement has no grounding in reality is another thing. It is part and parcel of the Fermi paradox.

Why would they have "colonized Earth" before we arose? Why would they do such a thing? Do you mean to tell me a species is going to travel 1000, 5000, 10,000, or 50,000 light years across the galaxy to live on our modest planet? They're going to skip over every other planet between here and there? How do you know that Earth's climate is even hospitable to those civilizations? Perhaps nitrogen is toxic to them. Wouldn't it be easier to colonize a planet with little existing atmosphere, to have a clean slate for "building" the proper atmosphere for the species? Surely there is a planet closer than thousands of light years away.

This is an appeal by ridicule (a logical fallacy). Appeals to ridicule are often accompanied with a straw man argument, and that is exactly what you have done here. One argument in favor of the Fermi paradox is that an intelligent species capable of colonizing the stars will colonize every single planet capable of sustaining their life. They would not have come from their home planet to Earth, bypassing every other planet along the way. That is ridiculous, and that is not what LURCH said.

One argument against the Fermi paradox is that a space-faring civilization might have rules against colonizing planets with intelligent life (which appears to be what LURCH was getting at), or even more stringent rules against colonizing planets with complex life, or even more stringent rules against colonizing planets with any life at all.

In short, your prediction that any alien civilization would have colonized Earth by now if they are older than 1,000,000 years old is flat-out absurd.

Try again without resorting to insults and logical fallacies.

The Drake Equation estimates a range between 1 (us,) and hundreds of thousands.

The lower limit is a lot, lot less than one. Even a value of 10^-7 would be consistent with the known fact that at least one communicative species (us) has appeared in our galaxy.

A 1G continuous acceleration rocket could take us from one edge of the Milky Way to the other in just 12 years travel time.

In whose frame of reference?

In the reference frame of the occupants of the space vehicle, obviously. There is one key conceptual problem with N721YG's 12 year figure: It assumes the spacecraft continuously accelerates in the same direction. It will take nearly twice as long (proper time) if the spacecraft is to come to a stop.

Now, if you mean from the point of reference inside the accelerating rocket, I don't know the math of Einstein's relativity enough to calculate it.

Learn it then. http://math.ucr.edu/home/baez/physics/Relativity/SR/rocket.html

 

[Jack21222]

One argument in favor of the Fermi paradox is that an intelligent species capable of colonizing the stars will colonize every single planet capable of sustaining their life.

It's an absurd argument. With approximately 200 billion stars, even if only 50% had only one world capable of sustaining their life (with the help of terraforming, for example), that still leaves 100 billion planets to colonize. I don't see how that's even remotely possible in a mere 1 million years.

If somebody is going to put forth such a laughable argument, don't get upset when it gets laughed at.

The lower limit is a lot, lot less than one. Even a value of 10-7 would be consistent with the known fact that at least one communicative species (us) has appeared in our galaxy.

I concede that point, with the caveat since we exist, it puts an artifical lower limit of 1 when the equation is used to attempt to solve "How many are there right now," and not the more general "How many in any given period."

In the reference frame of the occupants of the space vehicle, obviously.

That wasn't made obvious. More than one person was confused by it his assertion. It has been cleared up now.

Learn it then.

Taking my first semester of calculus-based physics starting tomorrow. I'll learn it in due time.

 

[Nabeshin]

It's an absurd argument. With approximately 200 billion stars, even if only 50% had only one world capable of sustaining their life (with the help of terraforming, for example), that still leaves 100 billion planets to colonize. I don't see how that's even remotely possible in a mere 1 million years.

If somebody is going to put forth such a laughable argument, don't get upset when it gets laughed at.

http://en.wikipedia.org/wiki/Von_Neumann_probe

 

[D H]

It's an absurd argument. With approximately 200 billion stars, even if only 50% had only one world capable of sustaining their life (with the help of terraforming, for example), that still leaves 100 billion planets to colonize. I don't see how that's even remotely possible in a mere 1 million years.

If somebody is going to put forth such a laughable argument, don't get upset when it gets laughed at.

It is anything but an absurd argument. Stop using appeals to ridicule. You are not making a good start here.

Various estimates for how long it would take to colonize the galaxy range from 1 to 10 million years. Here are a couple in the middle of that range:

"Assuming a typical colony spacing of 10 light-years, a ship speed of 10 percent
that of light, and a period of 400 years between the foundation of a colony and its
sending out colonies of its own, the colonization wave front will expand at an
average speed of 0.02 light-year a year. As the galaxy is 100,000 light-years
across, it takes no more than about five million years to colonize it completely." Source: Crawford, I.A., "Where are They? Maybe we are alone in the galaxy after all", Scientific American, July 2000, 38-43, (2000). http://www.cc.nctu.edu.tw/~tseng327/nctu-origin/article/sc200007a.pdf

"A colonizing, space-faring civilization which exercises population control will colonize the Galaxy in about 5×10⁶ years. This result assumes population growth rates and emigration rates appropriate to human experience and a 0.1c ship speed. The results are independent of the optimum population. Only with extreme assumptions is the colonization wave velocity less than 0.01 c." Source: Jones, E.M., "Colonization of the Galaxy", Icarus, Volume 28, Issue 3, July 1976, Pages 421-422 (1976). http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WGF-47318KS-285&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=6ae4f42af7c7090b33cddd257abf7f3a

I concede that point, with the caveat since we exist, it puts an artifical lower limit of 1 when the equation is used to attempt to solve "How many are there right now," and not the more general "How many in any given period."

You are misconstruing what the Drake equation is (beyond being a complete kludge). It is in essence a single-chain conditional probability calculation. The end result is the mean number of extant communicative civilizations at any point in time.

 

[N721YG]

That wasn't made obvious. More than one person was confused by it his assertion. It has been cleared up now.

I suspect any confusion was that many think it would take 100,000 years at the speed of light to cross the Milky Way. My intent was to point out it takes much less time. 12 years to cross and I did later add 24 if you want to stop (and live). 12 years, 24 years or 100 years, the point was made.

D H also makes some good points about good manners in these forums. Unless you have the credentials of Einstein, Your opinion is just that, an opinion. Your presentation when disagreeing with some one says it all.

 

[Jack21222]

Various estimates for how long it would take to colonize the galaxy range from 1 to 10 million years. Here are a couple in the middle of that range:

That's not what LURCH said, though. LURCH said,

If another civilization exists within this galaxy, it would have to be less than 1,000,000 yrs old, or they would have collonized Earth before we arose. This is a very narrow window, and makes it unlikely that such a civilization currently exists.

Emphasis mine. There is no compromise in that statement. There is no "perhaps," or any such verbiage in that statement. LURCH is stating unambiguously that there is a specific upper limit on the age of a civilization before they colonize the entire galaxy. This isn't even taking into account the fact that there is no guarantee a civilization would want to colonize the entire galaxy.

With so many moving parts, LURCH can in no way, shape or form state there is a "very narrow window." If LURCH had put in some ranges, add some qualifying statements, thrown in a heavy dose of uncertainty, I would have had no issue with the statement. But when phrased as an absolute, as if there were some hard cap as to how long a civilization can exist without colonizing the entire galaxy, I can't take it seriously.

Whoops, there I go appealing to ridicule.

 

[Chronos]

It's a long way between stars and hugely expensive to explore. I doubt most rational civilizations would be willing to make the investment.

 

[Arch2008]

When the Spanish royalty funded Columbus’ expedition, he didn’t have to create the National Seafaring Administration or hijack German scientists to create the technology for the ships or invent Velcro or Tang. Everything was already in place really and the expense was no more than any other maritime commercial venture of the time. So if Columbus hadn’t done it, then someone else eventually would have. I think that this ‘Columbus Paradigm’ applies to colonizing the universe too.
Eventually, the Earth will no longer provide enough living space for humanity. However, habitats in orbit can use energy from the Sun and resources from asteroids or the Moon to do this. As construction material improves, these self-sustaining habitats could eventually grow to the size of cities with populations of millions. The citizens of these habitats would then comfortably live out their lives in a microcosm. There would eventually be millions of these habitats in orbit around the Sun. Now add a fusion reactor for energy and a sail to anyone of these, and then a solar powered laser could move the habitat to a nearby star at near the speed of light and the inhabitants would barely notice.
Our ancestors supposedly lived in trees and caves. Today we build our homes from wood and stone. In the future, we will build habitats in space that resemble our ancient home on Earth. We or a similar alien civilization would not need to colonize any other planet. Each star system would provide energy and most likely building material to sustain growth by construction of habitats in space. A species that colonizes a galaxy most likely won’t stop there. There are millions of galaxies within migration distance of the Earth, but not one single contact.
So this is my speculation on the Fermi Paradox.

 

[D H]

That's not what LURCH said, though. LURCH said [some rather strong statements]. There is no compromise in that statement. There is no "perhaps," or any such verbiage in that statement. LURCH is stating unambiguously that there is a specific upper limit on the age of a civilization before they colonize the entire galaxy. This isn't even taking into account the fact that there is no guarantee a civilization would want to colonize the entire galaxy.

LURCH was quite emphatic in what he said. You could have pointed this out and asked for a justification for the statements he made in his post. That would have been a perfectly valid response.

That is not what you did. You instead argued with invective and with logical fallacies. Logical fallacies are not an acceptable form of argument here at PF, and invective is not an acceptable form of discussion. Some advice: Tone down your rhetoric and steer clear of fallacies. By doing so you will be taken much more seriously and you will avoid jumping on the ban wagon.

 

[N721YG]

...Eventually, the Earth will no longer provide enough living space for humanity...

Scientist say we are already using 30% more resources then the Earth can sustain and by 2050 it will take two Earths. Most seem oblivious to the obvious out come in their children's future. Despite all the marvelous things humans have accomplished, it seems we may not have the "Right Stuff" to not become eventually extinct. Now consider nuclear war, meteors, etc...

 

[D H]

Scientist say we are already using 30% more resources then the Earth can sustain and by 2050 it will take two Earths.

Reference, please.

 

[N721YG]

Reference, please.

I believe it was the History channel where I first heard it but a Google search will find more articles then you can count. I am not sure who is the most reputable source but for starters.

http://www.redorbit.com/news/science/1594776/reckless_consumption_depleting_Earth's_natural_resources/index.html
"If our demands on the planet continue to increase at the same rate, by the mid-2030s we would need the equivalent of two planets to maintain our lifestyles," said WWF International Director-General James Leape.

Another interesting link to information is the world population clock.
http://www.peterrussell.com/Odds/WorldClock.php
The population of the planet is increasing by over 200,000 people per day. Every one of those people will require food and energy to survive. The food clock link on that website is interesting also. You will not believe how may chickens we consume every day.

I read in the news often about the oceans being depleted of fish, the rain forest shrinking and oil consumption is outrageous. As the forest shrink, the deserts grow and there are more people to fit in the equation. Climate change (natural or man made) will be devastating to the human race if we make it that far.

I would think that those participating in these forums would be most likely to be on top if this type of information and the last to stick their head in the sand. Technology is moving very fast to solve problems but I don't think fast enough. I better get back to work on my dooms day machine.

 

[Arch2008]

The possibility that we don’t survive to find alien life is of course reasonably real. However, I might caution that those 200,000 people born each day could develop skills or discover new skills that they would trade for food and energy, the way I do, to survive. The efficient use of our planet’s, and solar system’s abundant resources could support several million times the Earth’s current population for geological time periods. A single 10-mile wide nickel-iron asteroid has more ore than has been mined on Earth in all of history. Space habitats can collect vast amounts of virtually free energy from the Sun for eons. If we took the money they want to spend to save the planet (from our species) and used it to remove our species to NEO, then we certainly could all live in space habitats within a century. Most of the technology already exists to make this possible. Once we secure our survivability, then it’s just a matter of time before we find alien life.

 

[D H]

http://www.redorbit.com/news/science/1594776/reckless_consumption_depleting_Earth's_natural_resources/index.html
"If our demands on the planet continue to increase at the same rate, by the mid-2030s we would need the equivalent of two planets to maintain our lifestyles," said WWF International Director-General James Leape.

In short, environmental alarmism. Think about it this way. We are not yet a Type I civilization; we're not even close. World-wide energy consumption is 16 terawatts, a paltry 0.01% of the 174 petawatts of energy the Earth currently receives from the Sun. The WWF has pulled a page out of Enron's playbook -- creative accounting. The number in question is the WWF's "Environmental Footprint", defined as the ratio of WWF's accounting of "humanity’s demand on the biosphere" to the Earth's biocapacity (both expressed in area). The demand side assesses "the area of biologically productive land and sea required to provide the resources we use and to absorb our waste." The WWF attributes a demand of 0.6 Earths to offset the burning of petrochemicals.

 

[LURCH]

Wow, I need to check in on these threads more often! All I did was re-state the Fermi Paradox. I noticed that some in this thread were referring to it, so I thought it (or a summary of it) should be included within the thread content. Didn't think it would stir up such a hornet's nest. However, I did make some statements without my usual blizzard of qualifiers, and for that I apologize.

First, some other points that have come up;

I suspect any confusion was that many think it would take 100,000 years at the speed of light to cross the Milky Way. My intent was to point out it takes much less time. 12 years to cross and I did later add 24 if you want to stop (and live). 12 years, 24 years or 100 years, the point was made.

Although that statement is completely valid, I think that the reference frame of those observers not inside the vehicle is the one most pertinent to the current discussion. The absence of ET's in our backyard is a puzzle that relates to how much time it takes them to get here in our reference frame, not theirs, don't you think?

When the Spanish royalty funded Columbus’ expedition, he didn’t have to create the National Seafaring Administration or hijack German scientists to create the technology for the ships or invent Velcro or Tang. Everything was already in place really and the expense was no more than any other maritime commercial venture of the time. So if Columbus hadn’t done it, then someone else eventually would have. I think that this ‘Columbus Paradigm’ applies to colonizing the universe too.
Eventually, the Earth will no longer provide enough living space for humanity. However, habitats in orbit can use energy from the Sun and resources from asteroids or the Moon to do this. As construction material improves, these self-sustaining habitats could eventually grow to the size of cities with populations of millions. The citizens of these habitats would then comfortably live out their lives in a microcosm. There would eventually be millions of these habitats in orbit around the Sun. Now add a fusion reactor for energy and a sail to anyone of these, and then a solar powered laser could move the habitat to a nearby star at near the speed of light and the inhabitants would barely notice.

Although I see your position, I think it is built on the assumption that outward migration would be driven by necessity, and civilizations would only move on when all local resources are exhausted. I believe this assumption to be false. There is no known example of a life-form that stays where it is until forced to move. AFAIK, all species expand their range whenever they can, not when they have to.
Later in that same post;

...A species that colonizes a galaxy most likely won’t stop there. There are millions of galaxies within migration distance of the Earth, but not one single contact.
So this is my speculation on the Fermi Paradox.

I don't know as I agree with this statement, although it depends entirely on what one considers "within migration distance." The Large and Small Magilanic Clouds are about 200,000 ly away, and aside from them, it's all dwarf galaxies until Bernard's, which is more than a million and a half. To me, this makes traveling around one's own galaxy sound like an entirely different animal from intergalactic travel. A race that has the tech to go star-hopping over distances of 10 to 100 ly is still a long way from having the juice to go a million ly from one galaxy to another.

As for "...no guarantee a civilization would want to colonize the entire galaxy..." I can only repeat that there is no species in existence that does not expand its range whenever possible. According to all availabel data, life continues to spread out until it reaches a barrier it cannot surmount.

 

[Arch2008]

I was simply showing that every ocean-going vessel in Columbus’ age could make the voyage to the New World and that similarly every space habitat would by design be capable of an interstellar voyage.
I’ve read that there are millions of galaxies within a one billion LY radius of our galaxy. At .1c that would make them within range of migaration if the civilization became spacefaring 10 billion years ago. Just speculating.

 

[Nabeshin]

I was simply showing that every ocean-going vessel in Columbus’ age could make the voyage to the New World and that similarly every space habitat would by design be capable of an interstellar voyage.
I’ve read that there are millions of galaxies within a one billion LY radius of our galaxy. At .1c that would make them within range of migaration if the civilization became spacefaring 10 billion years ago. Just speculating.

Columbus' voyage was funded because the European royalty knew they would get results when he returned, in a year or so (my historical knowledge is not amazing, but you get the idea). No communication would even be possible with the home planet for decades, for the nearest stars.

 

[Arch2008]

No instant communication would be necessary. Millions of people living for generations in a habitat community might not even remember their "home world". They would decide to go to the next star system for any number of reasons.

 

[D H]

I was simply showing that every ocean-going vessel in Columbus’ age could make the voyage to the New World and that similarly every space habitat would by design be capable of an interstellar voyage.

The immense differences in scale in cost and time do not justify this false analogy. You assumed a lot of potentially false items:

Eventually, the Earth will no longer provide enough living space for humanity. However, habitats in orbit can use energy from the Sun and resources from asteroids or the Moon to do this. As construction material improves, these self-sustaining habitats could eventually grow to the size of cities with populations of millions. The citizens of these habitats would then comfortably live out their lives in a microcosm. There would eventually be millions of these habitats in orbit around the Sun.

I'll grant you all of this for the sake of argument. Now, first question: Where is the impetus to move on? The sun puts out a lot of energy and the solar system has lots of resources in the form of entire asteroids and lifeless planets to be plundered. Our descendants will have to begin depleting the resources of the solar system before the same kinds of population pressures that forced us to leave the planet make us consider leaving the solar system.

Now add a fusion reactor for energy and a sail to anyone of these, and then a solar powered laser could move the habitat to a nearby star at near the speed of light and the inhabitants would barely notice.

Too much handwaving! How many inhabitants on the vehicle? Do the math. You are talking about an exawatt laser, firing continuously for a long time. Now the vehicle gets to the star. How will it slow down? (The target star is presumably void of civilization and thus does not have an exawatt laser on hand.)

 

[N721YG]

In short, environmental alarmism...

Let me guess, republican. I usually vote conservative but that is just so I can keep my guns so I will be able to get food when things go down.

Lets say the "environmental alarmist" are 90% wrong. Then it would be your kids kids rather then you kids that endure the issues. Or do you believe we can continue reproducing like we are forever without problems from it? Do the pictures from space showing the desserts expanding and the forest getting smaller concern you at all?

 

[N721YG]

Although that statement is completely valid, I think that the reference frame of those observers not inside the vehicle is the one most pertinent to the current discussion. The absence of ET's in our backyard is a puzzle that relates to how much time it takes them to get here in our reference frame, not theirs, don't you think?

Not at all. It is just that things are taken out of context when read out of order.

In post #9 yenchin said:
" Space travel is not just about exploration though, it is essential for survival of any advanced species if they were to live pass the life time of their star. When the Sun goes into red giant stage, we had better have somewhere else to go by then (although one can just get into a space colony of some sort without traveling too far I supposed...)"

My first post concerning quick travel across the Milky Way in post #14:
"A 1G continuous acceleration rocket could take us from one edge of the Milky Way to the other in just 12 years travel time. Our likely destination would most likely be much less distance. Earth time may be many thousands of years but who cares if it is dying. It would be a one way trip to save the human race. "

Now it seems to make a lot of sense Don't you think?

 

[N721YG]

I was simply showing that every ocean-going vessel in Columbus’ age could make the voyage to the New World and that similarly every space habitat would by design be capable of an interstellar voyage.

I agree, There was a time when crossing the Atlantic was impossible. I am sure there were many folks back then thinking just like many in this forum are thinking now. It won't be that hard to do with the know how and equipment just like space flight is routine now. My parents would have laughed at anyone talking about space travel when they were young.

 

[Arch2008]

http://science.nasa.gov/headlines/y2008/31jul_solarsails.htm
"Solar sailing is the only means known to achieve practical interstellar flight,"
http://www.niac.usra.edu/files/studies/final_report/333Christensen.pdf
http://science.nasa.gov/newhome/headlines/prop08apr99_1.htm
http://aerospace.wcc.hawaii.edu/sail.html
Etc.
Sorry if I skipped over too much. I didn’t want to hijack the thread discussing really basic stuff. The problem of interstellar flight is that not only must the fuel accelerate the mass of the craft, but the fuel must accelerate the mass of the rest of the fuel as well. I read in a book where someone had done the math that to send a 10 ton craft to the next star would take several thousand tons of antimatter and a similar mass of matter. A solar sail uses light “pressure” to move through space and doesn’t carry its fuel. The light would come from an enormous orbital laser that receives virtually endless energy from the Sun and then aims a beam at the sail. By angling the sail to create drag the ship can be slowed. Interstellar travel is possible and a species that colonizes a galaxy will find a way to get to the next galaxy. As I mentioned, there are lots of reasons for people like me or aliens to go to other stars and galaxies. My ancestors came from Europe. I’ve never missed their ‘home continent’ and I sadly don’t communicate with any distant relatives there.

 

[D H]

http://science.nasa.gov/headlines/y2008/31jul_solarsails.htm
"Solar sailing is the only means known to achieve practical interstellar flight,"

Please. That is a quote from a solar sail fanatic. This ignores work (much more successful work) done in the realm of advanced propulsion techniques, and ignores other even more fanciful techniques (e.g., Bussard ramjets) that, like solar sails, are presently solidly in the realm of science fiction. From the same article, "To date, no solar sail has been successfully deployed in space as a primary means of propulsion."

Using a solar sail to launch a tiny unmanned probe to another star is science fiction but may well become science fact. Using a solar sail to launch a huge colonization spacecraft to another star is science fantasy.

 

[LURCH]

Not at all. It is just that things are taken out of context when read out of order.

In post #9 yenchin said:
" Space travel is not just about exploration though, it is essential for survival of any advanced species if they were to live pass the life time of their star. When the Sun goes into red giant stage, we had better have somewhere else to go by then (although one can just get into a space colony of some sort without traveling too far I supposed...)"

My first post concerning quick travel across the Milky Way in post #14:
"A 1G continuous acceleration rocket could take us from one edge of the Milky Way to the other in just 12 years travel time. Our likely destination would most likely be much less distance. Earth time may be many thousands of years but who cares if it is dying. It would be a one way trip to save the human race. "

Now it seems to make a lot of sense Don't you think?

Ah yes, now I follow you. Certainly the duration of the trip as experienced by those onboard the vehicle would be a significant factor regarding the decission to go or not.

 

[BoomBoom]

Do you mean to tell me a species is going to travel 1000, 5000, 10,000, or 50,000 light years across the galaxy to live on our modest planet?

What do you think we would do if we found a livable planet and had the means to get there?

I have no doubt we would colonize it. Why should an alien race be any different?

 

[Jack21222]

What do you think we would do if we found a livable planet and had the means to get there?

I have no doubt we would colonize it. Why should an alien race be any different?

My point was there is an immense number of worlds, and turning any of those into a livable planet seems more efficient than traveling halfway across the galaxy. Even if we had the means to get there, I'm having trouble imagining a time where the expense to do it would be anywhere near trivial.

Also, why might an alien race be different? Well, because they're an alien race.

Sorry, circular argument, logical fallacies don't fly here, right?

An alien race would most likely have grown up in an entirely different environment than we have on Earth. There's no guarantee that the same chemicals and temperatures we find necessary for life would work for them. If we can't even get into alien biology, there's simply no way we can even begin to look at alien psychology, in my opinion.

This all started when LURCH failed to put in any kind of qualifiers to his "1,000,000 year upper limit" to a civilization before they colonize everything. With so many unknowns, I wouldn't be comfortable guessing at such a thing with a range smaller than 3 orders of magnitude.

I apologize for my abrasive tone earlier. Seeing exact numbers (such as the Drake Equation "solution,") where ranges spanning many orders of magnitude should be threw me off a bit.

 

[D H]

My point was there is an immense number of worlds, and turning any of those into a livable planet seems more efficient than traveling halfway across the galaxy. Even if we had the means to get there, I'm having trouble imagining a time where the expense to do it would be anywhere near trivial.

Please stop using straw men. Nobody is saying that species would travel halfway across the galaxy to get here. That is a mischaracterization of the colonization argument. The colonization arguments says that an space-faring species would colonize every available planet in the galaxy in a fairly short period of time (10 million years constituting a short period of time compared to the age of the universe).

So, why hasn't this happened? There are after all several valid arguments against the Fermi paradox. Here are but a few:

• Colonization is sporadic. A colony set up by a space-faring species will be on its own. Some colonies will die, some will stay contended in their new home. This is the percolation argument. http://www.geoffreylandis.com/percolation.htp
  
  
• Space colonization is essentially impossible. Space travel even amongst the planets is presently an extremely expensive proposition. Even if a species does manage to expand beyond the bounds of its home planet, expanding beyond the bounds of its home star system may well be forever out of reach. http://www.antipope.org/charlie/blog-static/2007/06/the_high_frontier_redux.html
  
  
• Intelligent species don't last long enough to take the first step. They self-destruct.
  
  
• Intelligent species are so incredibly rare that we are for all practical purposes all alone. Stephen Webb, If the Universe Is Teeming with Aliens... Where Is Everybody? Fifty Solutions to Fermi's Paradox and the Problem of Extraterrestrial Life, Springer (2002). Webb provides 50 solutions to the Fermi paradox in this book. This is solution #50, and is his preferred solution.

 

[Jack21222]

Please stop using straw men. Nobody is saying that species would travel halfway across the galaxy to get here.

D H:

I was responding a specific post by BoomBoom saying that we would travel to a habitable planet if we had the means to get there. I said that we might not, because even if we had the means to get there, we'd likely also have the means to make a lot of easier steps. In that part of the post, I was not responding to aliens coming here, I was responding to the human species going elsewhere, and more specifically, the human species as it stands right now on Earth.

So, now who's using the straw man?