How Many Intelligent Civilizations Are In Our Galaxy?

[Teacher Mark 53]

Maggie McKee, space editor

We know of only one for sure (and some might argue even that's a stretch).

To make estimates, researchers have long used a relationship called the Drake equation, plugging in values for things like the galaxy's annual star formation rate and the fraction of stars that host planets (make your own estimate in this interactive equation). There's so much wiggle room in the variables, though, that estimates have ranged from one to a million.

Now, Duncan Forgan of the University of Edinburgh in Scotland has attempted to constrain the numbers a bit better.

In a paper published in the International Journal of Astrobiology, he says estimates using the Drake equation are limited in accuracy because they rely on average values for parameters such as the lifetime of a civilisation capable of communicating with Earth.

To estimate a distribution of values instead, he created a computer model of the Milky Way's stars, generated planets around them, and assigned life to some planets in the habitable zones of their stars. Then he used equations that take into account the random nature of evolution to determine if that life went on to develop intelligence. By running the model again and again, he came up with a range of values, and put errors on the various estimates.

He looked at three different scenarios for how life could develop, and here's what he found (from a university press release):

The first scenario assumes that it is difficult for life to be formed but easy for it to evolve, and suggests there are 361 intelligent civilisations in the galaxy.

A second scenario assumes that life is easily formed, but it struggles to develop intelligence, and suggests that as many as 31,513 other forms of life are estimated to exist.

Finally, he examined the possibility that microbial life could be passed from one planet to another during asteroid collisions, which gave a result of 37,964 intelligent civilisations in existence.

So, it would seem that even in his worst-case scenario, we are not alone. (Which raises the question first voiced by Enrico Fermi - where is everybody?)

Of course, Forgan admits that his own estimates rely on incomplete information about the types of planets around other stars. At the moment, our observations most easily detect giant planets at close distances to their stars - not exactly cosy conditions for life, at least as we know it.

On 5 March, NASA's Kepler telescope will set out to find the first Earth-like planets in the habitable zones around their stars, which would significantly tighten up our estimates of the distribution of alien worlds - and possible life - in our galaxy.

But even with a more complete survey of exoplanets, there may be problems in our estimations of their habitability. Recent research suggests that our notion of a habitable zone - a region where the temperature is right to allow liquid water to exist on a planet's surface - is too simplistic. Many other factors, including a planet's mass, atmosphere, composition and the way it orbits its nearest star, can all influence whether it can sustain liquid water.

Furthermore, our notion of life itself may be too Earth-centric - alien life may not be based on carbon and water. Forgan acknowledges this too:

It is important to realize that the picture we've built up is still incomplete, and even if alien life forms do exist, we may not necessarily be able to make contact with them, and we have no idea what form they would take. Life on other planets may be as varied as life on Earth and we cannot predict what intelligent life on other planets would look like or how they might behave.

So, in the end, while I think this research is a neat thought experiment, it still seems premature to put much weight on its conclusions.

For my part, I would love it if the number of intelligent civilisations in our galaxy is the same as the answer to life, the universe and everything: 42.

http://www.newscientist.com/blogs/shortsha...lisat.html#more

The paper:

http://arxiv.org/PS_cache/arxiv/pdf/0810/0810.2222v1.pdf

[Jasman0717 9]

With the sheer numbers I have to believe that out there somewhere is someone just like me wondering if I exist

[Yoink 7]

Its out there... just not sure what it is.

[Jasman0717 9]

Its out there... just not sure what it is.

Alien/predator Jerry Lewis like creatures

[Krikit 1,165]

For my part, I would love it if the number of intelligent civilisations in our galaxy is the same as the answer to life, the universe and everything: 42.

Haha. 42. That's the answer.

[Teacher Mark 53]

I'm sure "they" are out there. My question has always been are we being visited.

[Melrose Plant 1]

Oddly enough, I have discussed this question recently with our 9 year old son. I told him that is sure seems likely that there are other civilizations out there, but that we will never get to visit them, and they will never get to visit us unless Einstein's Theory of Relativity is someday proven wrong, and we invent the Warp Drive. Or somebody else does.

[NickD 203]

Ha, I believe the earth is the center of the universe and those are just little flashlights orbiting around us, including our own sun. And the earth is flat, State of Iowa, is undisputed proof of that. Least was taught to believe that.

Are we alone? Discovery Science certainly has enough programs on UFO's, don't watch those anymore. A common property is that UFO's all have big flashing lights to come and visit us and only go to our military, only abduct people while they are in bed, run experiments on them and return them back to their beds.

It makes perfect sense to me if time travel is possible, the time machine already as been invented.

While we use electromagnetic waves for communication, can only wonder if there is another media, gravitation waves are possible, but we don't even understand gravity. Just know, if we drop a rock on our toes, it hurts.

But nothing so far, does make for good science fiction movies, though.

And yes, we can certainly question if there is intelligence on earth, can't prove it by our leadership.

[Yoink 7]

Oddly enough, I have discussed this question recently with our 9 year old son. I told him that is sure seems likely that there are other civilizations out there, but that we will never get to visit them, and they will never get to visit us unless Einstein's Theory of Relativity is someday proven wrong, and we invent the Warp Drive. Or somebody else does.

I think there is clear theoretical proof that space travel is possible just not exactly practical... but with tech improvement it may perhaps come efficient one day:

Based on Alcubierre’s warp drive, a futuristic engine that uses dark energy to propel a spaceship faster than light, has been proposed, and could revolutionize space travel according to an article on the web site of Cosmos Magazine [1]. The idea is backed up by calculations made by physicists at Baylor University in Waco, Texas. Like something from Star Trek, their theory says that a spacecraft could travel at warp speed in a bubble of space-time, by manipulating dark energy, the mysterious invisible force accelerating the expansion of the universe. The spacecraft would essentially remain in the same place, while space-time ahead of the spaceship would shrink, expanding again behind it. Even if it is possible, though, a dark energy warp drive wouldn’t be very practical - the experts estimate it would consume the entire mass of Jupiter to move a spaceship just 10 meters at faster-than-light speed.

[NickD 203]

Ha, to prove the theories of the formation of the universe, not only need dark energy but dark matter as well. But probably should prove the existence of either before designing space craft around it.

[Jasman0717 9]

Oddly enough, I have discussed this question recently with our 9 year old son. I told him that is sure seems likely that there are other civilizations out there, but that we will never get to visit them, and they will never get to visit us unless Einstein's Theory of Relativity is someday proven wrong, and we invent the Warp Drive. Or somebody else does.

I think there is clear theoretical proof that space travel is possible just not exactly practical... but with tech improvement it may perhaps come efficient one day:

Based on Alcubierre's warp drive, a futuristic engine that uses dark energy to propel a spaceship faster than light, has been proposed, and could revolutionize space travel according to an article on the web site of Cosmos Magazine [1]. The idea is backed up by calculations made by physicists at Baylor University in Waco, Texas. Like something from Star Trek, their theory says that a spacecraft could travel at warp speed in a bubble of space-time, by manipulating dark energy, the mysterious invisible force accelerating the expansion of the universe. The spacecraft would essentially remain in the same place, while space-time ahead of the spaceship would shrink, expanding again behind it. Even if it is possible, though, a dark energy warp drive wouldn't be very practical - the experts estimate it would consume the entire mass of Jupiter to move a spaceship just 10 meters at faster-than-light speed.

Some civilizations may have had millions of years to prefect space flight

[Waldo 0]

I give it a 50% chance of there "Yes" being life out there. And a 50% chance of there "NO" being life out there.

[Yoink 7]

Oddly enough, I have discussed this question recently with our 9 year old son. I told him that is sure seems likely that there are other civilizations out there, but that we will never get to visit them, and they will never get to visit us unless Einstein's Theory of Relativity is someday proven wrong, and we invent the Warp Drive. Or somebody else does.

I think there is clear theoretical proof that space travel is possible just not exactly practical... but with tech improvement it may perhaps come efficient one day:

Based on Alcubierre's warp drive, a futuristic engine that uses dark energy to propel a spaceship faster than light, has been proposed, and could revolutionize space travel according to an article on the web site of Cosmos Magazine [1]. The idea is backed up by calculations made by physicists at Baylor University in Waco, Texas. Like something from Star Trek, their theory says that a spacecraft could travel at warp speed in a bubble of space-time, by manipulating dark energy, the mysterious invisible force accelerating the expansion of the universe. The spacecraft would essentially remain in the same place, while space-time ahead of the spaceship would shrink, expanding again behind it. Even if it is possible, though, a dark energy warp drive wouldn't be very practical - the experts estimate it would consume the entire mass of Jupiter to move a spaceship just 10 meters at faster-than-light speed.

Some civilizations may have had millions of years to prefect space flight

yes but it is quite clear that communication out-techs travel. If a civilization were capable of inter-stellar travel they would have been able to send messages decades if not hundreds or thousands of years earlier

[mendeleev 68]

"How many intelligent civilizations are there in our galaxy?"

At times, I get discouraged and find evidence for none.

[Yoink 7]

"How many intelligent civilizations are there in our galaxy?"

At times, I get discouraged and find evidence for none.

Our galaxy is small compared to the universe we exist in. The Milky Way is just one galaxy or many many many x many