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We live at the beginning of the time when life is possible

  1. May 23, 2012 #1
    Because it take about 3 generations of stars to build enough carbon to the point where life is possible, roughly 9 billion years, our Earth therefore was among one of the first planets that housed enough carbon to make life possible. Stars will continue to exist for hundreds of billions of years. But according to Paul Davies in his book the Cosmological Jackpot:

    And Alex Vilenkin in his book Many Worlds in one puts the limit on the life span of matter at

    In other words, life might be possible from 9 * 109 to 1031 and we live practically at the beginning of that span. I find this fishy. Does anyone else? I'm not sure what this fact means, but I'm interested to hear what other people have to say.
  2. jcsd
  3. May 23, 2012 #2


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    Doesn't seem odd or fishy to me. It seems to be based on what we know about the universe right now, and that's a fair amount, even with some big gaps. What is it about it that bothers you?
  4. May 23, 2012 #3
    If you choose a number between 1 and 10^20 you should choose something in the middle, not something right near the beginning.
  5. May 23, 2012 #4


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    Yes, but that's math. This is reality. It is inevitable that early life in the universe will wonder WHY it is the early life in the universe, so if we ARE early life then ...
  6. May 23, 2012 #5
    Yes, it is inevitable that we will wonder why, but that is not an answer as to why we live at the beginning of the age of the habitable zone.
  7. May 23, 2012 #6
    I don't know how to calculate standard deviations, maybe I'll look it up, but I would seriously like to know how many stadev we are away from the likely habitable zone.
  8. May 23, 2012 #7


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    Well, hey ... SOMEBODY has to. Why not us?
  9. May 23, 2012 #8
    That answer doesn't make the fishiness go away.
  10. May 23, 2012 #9
    My first thought is that carbon based 'life' appears very opportunistic, perhaps emerging far more simply than we so far imagine. That could be a subject for another forum. There was a meteor or some other object recently tested and one of the AGTC building blocks was found in it! I still wonder where that object might have originated.

    It seems you think earth may be unique in some way? It seems more likely to me there are billions upon billions of carbon life form habitable objects, planets included. One thing for sure, life during a period when there were not the necessary elements for it is unlikely. So I'm not surprised it popped up when it could; Quantum theory almost demands it should do so.

    Would you find our situation less 'fishy' if other non carbon perhaps more ancient life forms are discovered?

    The most distant light is we receive is from 'only' about 45 billion light years away; but a likely ‘minimum distance’ for the 'most distant matter' is about 360 billion light years or thereabouts. Maybe it’s infinity. So there is a lot more than we can see even if not infinitely more. Could lots of that be 'older than us??
  11. May 23, 2012 #10


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    9 billion years puts the earliest likely time for life arise in the universe [according to Vilenkin] at least a billion years before life on earth. That does not seem particularly odd. Like corn in a popper, the action can get pretty furious in a hurry after the first few pops.
  12. May 23, 2012 #11


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    You are looking at it wrong.

    What you're saying is tantamount to this:

    March is when the snow thaws and rain falls regularly, raising the water table. November is when rainfall drops off to near nil.

    Why is it that the there's so much growth in March/April? This seems fishy. Why shouldn't it strike a balance - somewhere in the middle - in July?
  13. May 23, 2012 #12


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    Robert, I'm trying to understand what's fishy. It seems to apply to EARTH history as well as cosmic, anytime you can define a long historical era and we happen to be living at or near the beginning.

    what's logically different for example if I make the reasonable prediction that humans or more evolved Earth species will continue to be able to put things in orbit for, say, 5 billion years?
    Define that kind of Earth life to be space-life "S-life" and remember I'm just looking at Earth history, not cosmic.
    Isn't it fishy?!! S-life is likely to exist for 5 billion years and we are living nearly at the start! S-life has only existed for around 60 years!!!

    I would not call it fishy, I would call it interesting. Something interesting to learn about and reflect on. Part of seeing ourselves in historical context.

    Maybe there is some logical difference you can explain to me. Life is hard to define, one doesn't know what's possible life-wise. You seem to have chosen to imagine CARBON chemistry life arising on planets in orbit around functioning stars. Call it PC-life for "planet&carbon". Sort of recognizably like the life we know. that then defines an era. The era during which PC-life exists.

    We can conjecture that this will be a long historical era and that we happen to be near the beginning of it. I don't know how near the beginning of PC-life we actually are but it doesn't matter so much. Suppose we are near the beginning of the PC-life era. That's nice, it is something to think about, reflect on. See ourselves as pioneers. But I don't immediately see it as fishy.

    Maybe you can explain.
  14. May 23, 2012 #13


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    There is actually a tangential story to say about this having to do with exponential expansion.

    Take the population of the earth. It is a fact that because population seems to move on an exponential growth curve, a person born at any time t will note something rather odd. That is that the number of people living in his or her era, is roughly the same order of magnitude as the number of people in history that are dead. Very Copernican, but also quite odd upon further reflection.

    Namely, assume that the observer wasn't that smart and didn't know that population growth was on an exponential. Any such observer would wonder why they seem to be in such a special place in time, when at any other time (given an infinite duration) naively the amount of dead people should be much much bigger. Of course, this isn't quite well defined, b/c there is no countably additive uniform probability measure over the integers.

    Mathematically this is a simplified version of this coincidence problem in cosmology under the influence of exponential mechanisms like Cosmic inflation. Asking whether such and such a coincidence is really odd or not boils down to how you regulate the probability measures. Alas, there is no canonical choice.
  15. May 23, 2012 #14
    That's a false analogy. Snow thaws in March due to a confluence of physical laws, namely position of the Earth at that time in the year, among other things. There is no physical law that obligates intelligent beings to exist in the beginning of the habitable age.
  16. May 23, 2012 #15


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    any life that gets intelligent enough to ask where they are in the timeline from beginning to end, soon that life will destroy itself. how long do you think the human race and our "world order" will last?

    not long.
  17. May 23, 2012 #16
    Sorry, Marcus but I really don't understand your point. I understand bit and pieces but not the whole of your meaning.
  18. May 23, 2012 #17
    You're arguing from ignorance when you conjecture that intelligent life will not last long. You have no knowledge of the life spans of other intelligent species, say, any species with radio technology, so you have nothing to draw your conclusion on.
  19. May 23, 2012 #18
    Here is another fishy coincidence. This is from Lawrence Krauss' A Universe from Nothing

    He doesn't reflect on why this has happened, he just states it.
  20. May 23, 2012 #19

    This is a separate issue, namely, why there are so many patterns in our number system. All of that I find much more problematic and much more spooky than the fact that we live in the beginning of the habitable age.
  21. May 24, 2012 #20


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    It is not really a seperate issue. The crux of the problem is in determining whether you are 'typical' or 'atypical' in the statistical sense of the word. Defining what that means precisely is thorny, as I tried to illustrate. Certain assumptions need to be put into the system before you can make a mathematically rigorous statement (its like wondering what the probability is to pull a small O(1) integer out of the set of all positive integers)

    For instance, if you lived in a universe where there was an exponentially growing distribution of life giving planets, then it doesn't matter when you were born. The value 't' is irrelevant, b/c no matter what value 't' takes (young, old, very old), you will always be in an era where there were about as many observers before as there are in the present. However if you don't realize that you are in an exponentially growing phase, and instead simply try to put a uniform probability measure on the space, you end up making all sorts of wrong conclusions.
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