10 ms·

This article does a good job of covering a lot of different ideas on this paradox. I have a problem with the idea of "big numbers" in it though, like where it i

by gpsx 12y ago

This article does a good job of covering a lot of different ideas on this paradox. I have a problem with the idea of "big numbers" in it though, like where it implies 500 billion billion is nearly infinite, or that one-in-a-billion is a freak occurrence. There is a saying that if enough monkeys pound on a keyboard, one will type Hamlet. This would take a lot of monkeys. If we take the odds of hitting one character to be 1 in 40 (which doesn't account for properly hitting the shift key to make a capital), factoring in the 130,000 letters in Hamlet (according to Wikipedia), we get the odds of a monkey typing it at 6x10^208267. This number comes from 40 keys and 130,000 letters. How about when we start taking molecular numbers of items (6x10^23) and start raising that to a large power? I don't think it is a given that the number of planets out there infer there should be other life.

_greim_ 12y ago
We can't calculate the probability of life arising though because even if we did know how it arose here—which we don't exactly—we don't know all the possible different ways it can arise, which may or may not also be a number raised to a large power.
- gpsx 12y ago
  That is a good point. I agree with you. And people do have suggestions as to how life can be more probable than naively expected. But this answers the question why there is life at all as opposed to why we don't see more of it. My bias is that life is highly improbable and that we will not find any other life in our universe. But I also think it is no miracle that we exist, as I will describe. Given that I am trying to say this in one paragraph, it may not sound well justified, but it is how I view the problem. I'll start with Schrodinger's cat. A cat is in a box with some radioactive source that can decay and kill the cat. You can ask if the cat is alive or dead - and the answer is both. I will ignore the next part (Schrodinger's whole point) about what happens when the human observes it. There are different interpretations about why the human thinks the cat is definitely in one of the two states as opposed to both. This has to do with the human's observation and is not important for now. The point is that the cat is in both states. The universe can be in multiple states, some with life on earth and some without. Every possible state that can exist, does. So no matter how improbable we are, we will exist in some version of the universe. And there would be lots of other life too, just maybe not in our version of the universe. So the probability of life existing doesn't impact whether or not we should exist, but it does impact whether or not we see other life. I don't think we will. But as correctly pointed out, we don't know the answer to this right now.
  - conesus 12y ago
    The universe may / be as great as they say / but it wouldn't be missed / if it didn't exist. - Piet Hein
  - jacquesm 12y ago
    > My bias is that life is highly improbable and that we will not find any other life in our universe. It's probable enough for you to be writing this. The only options are 0, one and many. We can rule out '0'. That leaves us to decide whether the chances of us being the only one are larger than the chances that we are one of many. Obviously the second one has more chance of being true the one where there is only one. But we like to consider ourselves to be special so most people will believe the 'one'. Just like the sun used to revolve around the earth, now we're essentially seeing the universe as revolving around us. The alternative, that we're not special is not compatible with a lot of our collective culture.
    - gpsx 12y ago
      The point is that there are multiple universes, according to the quantum mechanics interpretation I subscribe to. So all of your options are true: 0, 1 and many. My position, which is admittedly no better than a guess, is that most universes by a far majority have 0. By virtue of me writing this, among other things, we live in a universe with at least 1. Again, my position would be that it is unlikely we have more than 1 in our universe. What you are saying it true under the assumption there is a single universe.
      - darkmighty 12y ago
        I think you're trying to articulate is the Anthropic principle [1]. It basically states that the probability that "some" life exists is 1. I'm not sure what the name of this next one is, but I believe it's a widely defended scientific principle that we're "typical" in some sense. This principle gets hard to justify cosmologically (it reduces to Occam's Razor locally), but it makes sense to me. It rejects very clearly some quirks like the Bolztmann Brain [2] argument. [1] http://en.wikipedia.org/wiki/Anthropic_principle http://en.wikipedia.org/wiki/Anthropic_principle [2] http://en.wikipedia.org/wiki/Boltzmann_brain http://en.wikipedia.org/wiki/Boltzmann_brain
- danieltillett 12y ago
  We can't calculate the probability of life arising though because even if we did know how it arose here—which we don't exactly—we don't know all the possible different ways it can arise, which may or may not also be a number raised to a large power. We can't, but we can assume that any process that arises from a series of unlikely chained events (where the likelihood of each event are not correlated) will most likely occur near to the latest time possible. For example, if you run a trillion parallel 10-step chained experiments over a year starting at Jan 1 where each step is very unlikely to occur so that only 100 reach step 10, then the last steps are all likely to occur in December. The less likely each step is (or the more steps involved) then the more the experiments that reach the final step will cluster towards Dec 31. If you have a group of such events then you can actually calculate the likelihood of the chain series. Intelligent life in a large universe is a similar to this imaginary experiment. While we only have one observed data point, we do know how close the appearance of intelligent life on earth is to the last possible time that it could occur. Outside of our geologically recent anthropogenic boost to the CO2 in the atmosphere, the long term trend of CO2 concentrations in the atmosphere is down (this is due to the sun becoming warmer over time requiring CO2 to be removal from the atmosphere to keep earth in the habitable temperature range). We are in geological terms close to the point where any further removal of CO2 will mean photosynthesis will no longer work (plants are already CO2 limited) - maybe a few 10 millions years. In geological time this is very close to our Dec 31. What does this all mean? Basically it appears humans have evolved close to the latest time point possible. While we can't calculate the exact probability of intelligent life arising in the universe from our one example, we can say that the evolution of humans is consistent with the hypothesis that the evolution of any intelligent life in the universe is very unlikely.
  - dennisgorelik 12y ago
    Why do you think that current CO2 concentration levels are important for intelligent life? Slight adjustment in how body works can easily adapt organism to new CO2 levels.
    - danieltillett 12y ago
      I did explain it in my post, but maybe it was too short. Earth has been kept in the habitable temperature zone over the last 3.5 billion years through falling CO2 levels. Around 3.5 billion years ago the sun provided ~25% less energy than now and the CO2 levels were much higher. This is the green house effect. As the sun got brighter over time the level of CO2 in the atmosphere has fallen. For more on this see the slow carbon cycle [1]. The problem is that the level of CO2 in the atmosphere is getting very low (~0.2%). At this level plants are starved for CO2 - if it gets down to 0.01% then plants can't grow at all and the ecosystem needed to support the evolution of intelligent life would collapse. 1. http://earthobservatory.nasa.gov/Features/CarbonCycle/page2.php http://earthobservatory.nasa.gov/Features/CarbonCycle/page2....
- JoeAltmaier 12y ago
  I've always thought, given the right circumstances, life will always be formed. Instead we should be calculating the odds of life NOT forming e.g. the half-life of staying-dead. Our planet has carbon, oxygen, water, the right temperature, a moon that sloshes it all around, rotation. Every grain of sand on every beach is going through a different cycle of heating/cooling + wetting/drying + different salts and ions depending on the local environment. For a billion years it was this enormous biochemistry experiment. Life pretty much HAD to happen, somewhere in all that.
ghaff 12y ago
This is essentially the problem that I have with the Drake equation. It encourages--whether that's the intent or not--taking a reasonably known and very, very large number (number of stars) and multiplying it by probabilities/percentages, some of which (we think) we know with at least order of magnitude accuracy. But others we have absolutely no idea. And saying some of those events (such as the evolution of intelligence as we understand the term) has a 1 in a billion probability of occurring SOUNDS like a worst case for-the-purposes-of-argument plug-in. But it's really not.
- greendestiny 12y ago
  Another example I hate is the probability of reality being a simulation thought equation. If these equations had some confidence interval based on how little we know it would be clear how meaningless they are.
venomsnake 12y ago
Depending of whether life is a fluke or normal outcome. Until we know how life on Earth began, we will have no idea for what to look for in the sky. http://www.scientificamerican.com/article/a-new-physics-theory-of-life/ http://www.scientificamerican.com/article/a-new-physics-theo... This theory could be quite important or wrong. Or both. But it gives very interesting definition of what life is.

by gpsx 12y ago

_greim_ 12y ago

We can't calculate the probability of life arising though because even if we did know how it arose here—which we don't exactly—we don't know all the possible different ways it can arise, which may or may not also be a number raised to a large power.

gpsx 12y ago
That is a good point. I agree with you. And people do have suggestions as to how life can be more probable than naively expected. But this answers the question why there is life at all as opposed to why we don't see more of it. My bias is that life is highly improbable and that we will not find any other life in our universe. But I also think it is no miracle that we exist, as I will describe. Given that I am trying to say this in one paragraph, it may not sound well justified, but it is how I view the problem. I'll start with Schrodinger's cat. A cat is in a box with some radioactive source that can decay and kill the cat. You can ask if the cat is alive or dead - and the answer is both. I will ignore the next part (Schrodinger's whole point) about what happens when the human observes it. There are different interpretations about why the human thinks the cat is definitely in one of the two states as opposed to both. This has to do with the human's observation and is not important for now. The point is that the cat is in both states. The universe can be in multiple states, some with life on earth and some without. Every possible state that can exist, does. So no matter how improbable we are, we will exist in some version of the universe. And there would be lots of other life too, just maybe not in our version of the universe. So the probability of life existing doesn't impact whether or not we should exist, but it does impact whether or not we see other life. I don't think we will. But as correctly pointed out, we don't know the answer to this right now.
- conesus 12y ago
  The universe may / be as great as they say / but it wouldn't be missed / if it didn't exist. - Piet Hein
- jacquesm 12y ago
  > My bias is that life is highly improbable and that we will not find any other life in our universe. It's probable enough for you to be writing this. The only options are 0, one and many. We can rule out '0'. That leaves us to decide whether the chances of us being the only one are larger than the chances that we are one of many. Obviously the second one has more chance of being true the one where there is only one. But we like to consider ourselves to be special so most people will believe the 'one'. Just like the sun used to revolve around the earth, now we're essentially seeing the universe as revolving around us. The alternative, that we're not special is not compatible with a lot of our collective culture.
  - gpsx 12y ago
    The point is that there are multiple universes, according to the quantum mechanics interpretation I subscribe to. So all of your options are true: 0, 1 and many. My position, which is admittedly no better than a guess, is that most universes by a far majority have 0. By virtue of me writing this, among other things, we live in a universe with at least 1. Again, my position would be that it is unlikely we have more than 1 in our universe. What you are saying it true under the assumption there is a single universe.
    - darkmighty 12y ago
      I think you're trying to articulate is the Anthropic principle [1]. It basically states that the probability that "some" life exists is 1. I'm not sure what the name of this next one is, but I believe it's a widely defended scientific principle that we're "typical" in some sense. This principle gets hard to justify cosmologically (it reduces to Occam's Razor locally), but it makes sense to me. It rejects very clearly some quirks like the Bolztmann Brain [2] argument. [1] http://en.wikipedia.org/wiki/Anthropic_principle http://en.wikipedia.org/wiki/Anthropic_principle [2] http://en.wikipedia.org/wiki/Boltzmann_brain http://en.wikipedia.org/wiki/Boltzmann_brain
danieltillett 12y ago
We can't calculate the probability of life arising though because even if we did know how it arose here—which we don't exactly—we don't know all the possible different ways it can arise, which may or may not also be a number raised to a large power. We can't, but we can assume that any process that arises from a series of unlikely chained events (where the likelihood of each event are not correlated) will most likely occur near to the latest time possible. For example, if you run a trillion parallel 10-step chained experiments over a year starting at Jan 1 where each step is very unlikely to occur so that only 100 reach step 10, then the last steps are all likely to occur in December. The less likely each step is (or the more steps involved) then the more the experiments that reach the final step will cluster towards Dec 31. If you have a group of such events then you can actually calculate the likelihood of the chain series. Intelligent life in a large universe is a similar to this imaginary experiment. While we only have one observed data point, we do know how close the appearance of intelligent life on earth is to the last possible time that it could occur. Outside of our geologically recent anthropogenic boost to the CO2 in the atmosphere, the long term trend of CO2 concentrations in the atmosphere is down (this is due to the sun becoming warmer over time requiring CO2 to be removal from the atmosphere to keep earth in the habitable temperature range). We are in geological terms close to the point where any further removal of CO2 will mean photosynthesis will no longer work (plants are already CO2 limited) - maybe a few 10 millions years. In geological time this is very close to our Dec 31. What does this all mean? Basically it appears humans have evolved close to the latest time point possible. While we can't calculate the exact probability of intelligent life arising in the universe from our one example, we can say that the evolution of humans is consistent with the hypothesis that the evolution of any intelligent life in the universe is very unlikely.
- dennisgorelik 12y ago
  Why do you think that current CO2 concentration levels are important for intelligent life? Slight adjustment in how body works can easily adapt organism to new CO2 levels.
  - danieltillett 12y ago
    I did explain it in my post, but maybe it was too short. Earth has been kept in the habitable temperature zone over the last 3.5 billion years through falling CO2 levels. Around 3.5 billion years ago the sun provided ~25% less energy than now and the CO2 levels were much higher. This is the green house effect. As the sun got brighter over time the level of CO2 in the atmosphere has fallen. For more on this see the slow carbon cycle [1]. The problem is that the level of CO2 in the atmosphere is getting very low (~0.2%). At this level plants are starved for CO2 - if it gets down to 0.01% then plants can't grow at all and the ecosystem needed to support the evolution of intelligent life would collapse. 1. http://earthobservatory.nasa.gov/Features/CarbonCycle/page2.php http://earthobservatory.nasa.gov/Features/CarbonCycle/page2....
JoeAltmaier 12y ago
I've always thought, given the right circumstances, life will always be formed. Instead we should be calculating the odds of life NOT forming e.g. the half-life of staying-dead. Our planet has carbon, oxygen, water, the right temperature, a moon that sloshes it all around, rotation. Every grain of sand on every beach is going through a different cycle of heating/cooling + wetting/drying + different salts and ions depending on the local environment. For a billion years it was this enormous biochemistry experiment. Life pretty much HAD to happen, somewhere in all that.

ghaff 12y ago

This is essentially the problem that I have with the Drake equation. It encourages--whether that's the intent or not--taking a reasonably known and very, very large number (number of stars) and multiplying it by probabilities/percentages, some of which (we think) we know with at least order of magnitude accuracy. But others we have absolutely no idea. And saying some of those events (such as the evolution of intelligence as we understand the term) has a 1 in a billion probability of occurring SOUNDS like a worst case for-the-purposes-of-argument plug-in. But it's really not.

greendestiny 12y ago
Another example I hate is the probability of reality being a simulation thought equation. If these equations had some confidence interval based on how little we know it would be clear how meaningless they are.

venomsnake 12y ago

Depending of whether life is a fluke or normal outcome. Until we know how life on Earth began, we will have no idea for what to look for in the sky. http://www.scientificamerican.com/article/a-new-physics-theory-of-life/ http://www.scientificamerican.com/article/a-new-physics-theo... This theory could be quite important or wrong. Or both. But it gives very interesting definition of what life is.