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Age of universe -- Probability why it is so young?

  1. May 31, 2015 #1
    I'm a retired geologist ... Know little about cosmology or quantum physics so will defer to others.

    Please excuse my rambling question.

    Something has always 'made me wonder' about the potential fate of the Universe. Almost all models predict either an infinite Universe or a Universe that undergoes some end or cycle that is hundreds of billions or trillions of potential years.

    Bottom line. The Universe is only 13.7 billion years old. The Universe, according to almost all models is not a hundreth or even a thousand...in some models a millionth...of its potential age. If there is an infinity then, 13.7 billion isn't a mote on a dot on a number line.

    The Universe is a baby. Barely getting going. 13.7 billion years is a blip in time compared to how old the universe could be at a random moment of time in its history. Throw a thousand numbers into a box and pick the number 'one' out at random...if it is the age of the current Universe, it would still be the equivalent to the number 'one' according to some models. That's always seemed a stretch to me. Why are we at 'now' almost at the beginning of time and not further along.

    Yes, the Universe has to be at some point in its existence. However the point that is 'now' seems the equivalent of a random chosen human being one day old...possible but highly improbable...one in tens of thousands. One would think that 13.7 billion years old would be somewhere further along a scale.

    Anyways...my question...are there models of the Universe that would put the Universe further along the percent of its life cycle? Is there a model in which the Universe has a finite life span of 20 or 30 or 50 billion years? Some age that makes 13.7 seem more probable to be 'now'.
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  3. May 31, 2015 #2

    Simon Bridge

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    Welcome to PF;
    They usually assume the overall geometry and then use projections based on that to make prediction like how much longer the Universe has to go.

    OK you mean that we find ourselves in a Universe that is near the start of it's life rather than, say, near the end?

    As a geologist you will be aware of the age of the Earth compared with the total projected life of the Sun ... have you ever wondered how it is that we should appear on the Earth at this articular time?

    Since you have only seen one throw of the dice, it is impossible to estimate the odds that a particular number will show up. Some number has to show up, why assume any particular one more or less likely than any other?
    If you look out at a road and note the licence plate of the first car you see, you will find that particular one pretty unlikely (if you exclude your own car). The same arguments you posed above could be made about that plate number ... why that one?

    OTOH: perhaps it takes a certain amount of time for intellegent life to show up to wonder about the age of the Universe?

    Note: there are always whimsical and speculative cosmologies ... I understand the most popular one has the current age of the Universe at order 10,000years and the end of time in order 1000 years or less. These sorts of models are too speculative for PF, all we can talk about is what the best models we have show.
    Last edited: May 31, 2015
  4. May 31, 2015 #3


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    There's really no way to compare probabilities with respect to when you were born. For example, if human civilization stabilizes at about 7 billion people and lasts just a few hundred more years, then nearly every person who will ever live lives in the future. That doesn't make us experiencing the present unlikely, because somebody has to experience it for those future people to exist at all.

    Another way of saying this is that just because it's unlikely that you win the lottery doesn't mean that it's unlikely that anybody wins the lottery. And the person who does win should not doubt that they have won just because the probability is small.

    As far as the future, a nice overview of what will probably happen can be found on this Wikipedia page:
  5. May 31, 2015 #4
    Obviously you must exist at a time when the state of the Universe is compatible with your existence.
    You could not have existed in the earliest stages of the Universe, and you can't exist in the distant future when the Universe is thought most likely to end up in a cold degenerate state.
    It may well be that there is only a relatively short phase in the life of the Universe which actually is compatible with your existence so that phase is where you exist.
  6. May 31, 2015 #5


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    Rootone raises a valid point. A rocky planet like earth requires multiple supernova to supply the 'metals' that comprise it, so a rocky planet demands a universe old enough to birth a few generations of stars. The first stars are not believed to have formed until the universe was about 500 million years old. Earth is believed to have formed when the universe was about 9 billion years old. From that perspective, it appears the age of the universe is just about right.
  7. May 31, 2015 #6
    True. The current age of the Universe may be within 5 or 10 billion years ether side for us to be here and thus having a consciousness of it...to ask the questions.

    However, it is still highly improbable that existence to ask these questions would be 'now'. Improbable to one in a thousand...or some models one in a million, billion, etc.

    My feeling (unscientific) is the Universe probably has a finite life shorter than most models predict...since there are no physical evidence of this (just odds) then it lends itself to some outside influence...other Universes impacting our one. Then perhaps some cycle starts again. Perhaps some quantum half life does our Universe in.

    'Way back' I went to a talk by Carl Sagan. The theme wasn't why the Universe is so big (his billions and billions of stars) but the reverse...why is it so incredibly small. Things are large on our human perception level but a fraction the size on a conceptual level. Add a zero and it's 10 times as big... just 3 zeros and a thousand times bigger. We can conceive of a Universe of infinite size but the Universe that exists is a mote on a dot on a mathematical number line.
  8. May 31, 2015 #7


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    Any specific time is improbable. If you do the probability calculations correctly, the future state of or universe has precisely zero impact on the expected probability of existing at the current time.

    Edit: Though like I said, existing at a specific time is a dubious thing to think about probabilistically.
    Last edited: May 31, 2015
  9. May 31, 2015 #8
    I think the word here is anthropic. That is, the universe must be of the correct age and state that is compatible with that which observes it.

    That rules out a significant block of time between T0 and about 5 to 10 billion years ago. It's a little like discovering puberty. You won't find it in a 3-year old no more than an adult. It took many billions of years for the Milky Way to mature enough that we have Pop I metal rich stars and a new star formation rate that doesn't cook everything off the surface of the planets with radiation.

    As for the total age that the universe will exist, that's not really clear. If the universe is infinite, you can't expect it to remain at a steady state of existence and as such favorable for the purchase of life forever. How many billions of years will the universe continue to support life? Well, I submit to you that in about 2 to 3 billion years the merger with Andromeda will pretty much be an extinction type of event. Many stars will be cast out of the Milky Way and many more new stars will be born, cause waves of sterilizing radiation throughout the galaxy. It will take billions of years for things to stabilize again and possibly reboot.

    Our own little sphere of dirt just happens to be riding at just the right location in the Milky way to support like. Much closer or further from the core subjects it to much higher radiation. Not good. Our proximity to the spiral arms is also of good fortune. Inside the arms the radiation is also too high. We also orbit the galactic core at the same rate the arms we are trapped between do. That spares us from crossing an arm and being sterilized as we whirl around the galactic core once every 250 million years at 230 km/s.

    All of that seems like a very low probability, but then again, life would not take hold if we were anywhere else, so this is why we can philosophize such things, because of the anthropic principle - at least in part.
  10. May 31, 2015 #9


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    The anthropic principle is , IMO, a terrible basis for probability. It's a self eating watermelon - a local colloquialism, but, not necessarily right.
  11. Jun 1, 2015 #10


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    The strong anthropic principle is nonsense. The weak anthropic principle is true by definition. It can be applied poorly, but that doesn't mean it's invalid.

    I generally think that the best way to think about the anthropic principle is that it provides reasonable limits on what sorts of things we should be surprised about. If X is necessary for structure formation (which is a fundamental requirement of life), then it makes no sense to be surprised about X, because no observer could ever observe anything but X.
  12. Jun 1, 2015 #11
    That was my precise point and you did a nice job describing it. The anthropic principle provides a framework.
  13. Jun 1, 2015 #12
    I don't foresee anything having an impact on the existence of future intelligent life. Within a thousand years...or at least a couple thousand, we'll transcend immediate physical limitations of matter and energy ( unless something in quantum not understandable). No longer impacted my the chance happenings of stars, galaxies, etc. In a billion years!...Andromeda would be a play toy for any type of advanced intelligence.

    An aside...I once read that the impact on the Sun and solar system would be near zilch when our Galaxy and Andromeda merge. Stars are so far apart that not much of anything would happen at any local level and it would all be a non event (I could be wrong).
  14. Jun 1, 2015 #13
    You presume that we are the only life in the Milky Way or that I was simply referring to ourselves. We may or may not be here, but anything that remains or emerges during the merger will be in hard times compared to the mature calm we are used to.
  15. Jun 1, 2015 #14


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    I don't think you are wrong, I've read the same thing. Stars are so dispersed that encounters that actually disrupt planetary systems will be rare.
  16. Jun 1, 2015 #15
    One of the implications of 'some' Multiverse theory is there becomes room for infinite Existences...ones in which there is a weak anthropic element, others in which their is a strong anthropic element and others in which there could be a god that creates everything in six days. The same variations can arise with Holographic theories of physics...we're all in a big simulation, etc.

    I'm a strong atheist but find in the last decade or so that I've opened up my thinking to allow for some other possibilities outside of our thinking. For weirdo happenings...accelerating Universe, Quantum entanglement, etc. In my younger years I was confident we were on some track to figure out the essence of existence. Now?...it's as if we're fumbling more around the edges. Physics and Cosmology are more fascinating than ever.
  17. Jun 1, 2015 #16


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    There's no reason to believe this is true. The futurists who push this sort of thing generally have no solid data or even theory behind their claims.

    Ideally, humans will know a lot more about the universe a thousand years from now. But the idea of "transcending the limitations of matter and energy" is pure fantasy. I would love to know what happens to humanity for the next thousand, ten thousand, or hundred million years. But the common sci-fi tropes of advancing beyond the need for bodies are ridiculous.

    A play toy? No. The mass and energy involved in the upcoming merger between our galaxy and Andromeda is far, far too great for any conceivable technology to have an impact on it.

    This is largely correct. The biggest danger to life in our galaxy would be life-bearing stars ending up near a star-forming region during the merger. Such regions would create some extremely massive stars which would go supernova in short order, and a supernova that is close enough to us could sterilize the Earth.

    But no life on Earth will have to worry about this event no matter what: the merger isn't going to happen for another four billion years, while the Earth will cease to support life about a billion years from now. At that time, the increase in the Sun's temperature reaches a tipping point that leads to a runaway greenhouse effect the result of which is the oceans boiling...nothing will be able to survive that for long, and the Earth will become a sort of second Venus. If humans are to survive longer, we'll need to become an interstellar species, but the engineering challenges in making that occur are tremendous: it may actually be impossible.
  18. Jun 1, 2015 #17


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    to learn to enjoy life in subsurface caverns hollowed out in the moons of Jupiter and Saturn?

    Ceres is an ice-ball we could practice on. But there are a lot of others further out.
  19. Jun 1, 2015 #18


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    I think if you gave a detailed description of "we" it might be clear to a cosmic paleontologist that we most likely were living in the Teenage of the expansion process. There are details about us, and Earth life generally, which DATE us. Earth life, carefully examined, has a certain "nooby" or juvenile character, that you wouldn't likely find displayed in year 50 billion.

    Structure formation requires a certain density. Star-formation stops in galaxies at a certain point. Astronomers have identified "dead" galaxies which are no longer forming stars. (they can have biological life of course---they are only dead in the sense of stars and new planetary systems no longer forming.)

    Most bioforms that are still extant after year 30 billion, for instance, will probably have had to adapt to live in lower gravity places that didn't have enough mass to hold surface oceans and atmosphere. They will probably have a memory of life on previous planets. WE are unusual in the sense that we are still on our first planet, and we are surface dwelling life forms that need an atmosphere.

    Such things might still exist after year 30 billion, say, but they might be increasingly RARE as life forms then go.

    So a paleontologist might be able to inspect pictures of us and other Earth lifeforms, and read descriptions of our biochemical processes, and determine with HIGH PROBABILITY that we belonged to the first 30 billion years of the expansion. When galaxies had stopped condensing but when there was still plenty of star-formation going on in the galaxies that had already collected. Because we just LOOK like juvenile lifeforms that most likely arose during the first few billion years of our star's existence.

    So you ask why are WE living in, say, the first 30 billion years of the expansion? If you look at what we are like it seems there are telltale signs of earliness, earliness of star and planet formation, and chemistry, and biological evolution. Maybe you could say we are living in the first 30 billion years because we are the sort of life forms that there were then, in that period.

    Paleontologists have ways of dating and judging stuff like that. If they have gone over enough examples.
    You, as a geologist, have probably been exposed to the paleontology (of just this one planet, but it generalizes) and the accumulated understanding of how evolution proceeds.
    Last edited: Jun 1, 2015
  20. Jun 1, 2015 #19
    I am a paleontologist. Specializing in certain taxa of Paleozoic invertebrates.

    The issue with projecting into the future is that it doesn't account for intelligences manipulating matter and energy. The physical properties of the Universe are most likely rational and 'probably' understandable. If not in a thousand years...then in ten thousand. Even if humanity remains carbon based for the next million or 30 billion years...a carbon atom is not beyond our understanding. Nor will be the specific ingredients to make life...we are already on the cusp of this. Regardless what happens to the Universe at the larger scale...we will control more local events.

    My prediction is that if we were to fast forward just 10 thousand years, humanity would be on a hundred various pathways directed by genetic engineering. Customized 'everything' from super intelligence to physical beauty (I could use that one). Perhaps there are billions or quadrillions of intelligences already in some advanced stage that use matter and energy at their whim.
  21. Jun 1, 2015 #20


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    If there is ever a non-carbon-based life form that we create, it won't be humanity.

    Also, the carbon atom itself is fully-understood. Understanding of individual atoms is not the problem. The emergent behavior of trillions of atoms working together in complex ways is the problem. And it's a very, very difficult one.

    It'll be interesting to see. Genetic engineering presents lots of difficulties, across a variety of dimensions. It's entirely possible that we never do more than screen for certain genetic disorders (which is done today on a small scale, and is especially helpful for small communities with low genetic diversity). I think it would be neat to do more, but the biggest problem facing us right now is that the genome is incredibly complicated. One big problem is that most genes operate in networks (and sometimes the same gene will operate in more than one network). If you remove one gene from a network, many gene networks will continue to operate without problem. But remove a second one and they fail to function properly. This fact makes it incredibly difficult to track down the biological consequences of any one gene, and we are limited in our ability to learn the consequences of any given gene by the size of the human population. What this means, essentially, is that it may be impossible to determine the genetic influences for complex traits where most of the variance doesn't come from genetics anyway (such as intelligence).

    Maybe someday we'll figure out how to genetically engineer humans safely, but that day is a long, long way off. And the ethical issues with such modifications will remain no matter what (the ethical issues may make any foray into human genetic engineering short-lived).
  22. Jun 1, 2015 #21
    If humans evolve in the future to become something other than carbon based life forms, then our present understanding of evolution must be entirely wrong.
  23. Jun 1, 2015 #22


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    Not if "evolve" includes human technological advances. Our present theory of evolution in no way rules out an intelligent species choosing to "evolve" itself in a way that "unaided" evolution (i.e., evolution without the intelligent species involved) could not achieve.
  24. Jun 1, 2015 #23
    In that case though, natural selection is no longer applicable as the underlying mechanism, and familiar taxonomy would need to be scrapped.
    We would need a new theory of evolution based on inherited subroutines or even hardware generated interrupts!
  25. Jun 1, 2015 #24


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    Sure, but constructed beings, even ones that make use of human brain structure or data, will not be human in any meaningful sense. They'll be something quite different. In fact, even if they're sentient, it may not be accurate to think of them as being alive at all (reproduction through imperfect replication is probably the most general definition of life there is, and constructed beings probably wouldn't have that).
  26. Jun 1, 2015 #25
    To an extent a carbon atom is understood at a superficial macro level...not at the level of a Theory of Everything'. What makes everything exist? Tick? We are getting closer to the answer ...at least hopefully. We may actually know zip about reality...including carbon atoms. Completely off on a wrong tangent. It's happened a couple times in the history of physics.

    As for engineering safely and Ethical issues. That is a momentary blip of one society's restrictions. There is no worldwide government control. Private labs in China, India may start a genetic intelligence escalation. Let alone what may happen in a thousand years, million years, billion years. All lengths of time actually 'short term' in the scheme of things. Trillions of intelligences may have arose a few billions of years ago.

    What is evolution? Like most things in science, it depends on defining the term evolution. Then some phenomenon fits or doesn't within that definition. A thousand Sci fi books have dealt with 'What is human'...again all depends on defining terminology. In my field we constantly need to define 'species' when using that term as at times in geology we use it differently than in biology.
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