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Dear Marcus: Please explain

  1. Oct 8, 2011 #1
    Dear Marcus:

    Many thanks for your very informative messages.

    Please write one more on a simple LAYMAN's question.

    How do we know FOR SURE what is going on NOW in the far distant places of the Universe as the light from there had originated long AGO?

    Why there are no chances that NOW the far edges of the Universe are slowing in their move outward, or not expanding at all, or even contracting in a Big Crunch?

    As a stupid layman I think we do NOT and can NOT know anything about the places of the Universe about which we can get only a remote history. All we do are bold extrapolations.

    Dear Marcus:

    Please tell me where I am stupidly wrong so that I would stop thinking on this question and get peace of mind.

    Thank you,

  2. jcsd
  3. Oct 8, 2011 #2


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    When Marcus answers, I'm sure he'll give a more knowledgeable one than my amateurish one. The question does not seem to me to be in the least stupid. It's one that has been brought up here before and of course your logic is unassailable in that yep, it's been a long time since the light from far distant galaxies and other objects left on there way here and who knows what might be going on out there right now.

    One thing that points to the likelihood that there is NOT anything weird going on out there and that in fact our "bold extrapolations" (nicely phrased by the way) most likely are right, is the fact that the models physicists have come up with to explain how the universe works would likely be badly broken if weird stuff WAS happening "out there".

    I know that sounds a lot like "well it just DOESN'T and that's my story and I'm sticking with it", but I think it's a bit more sound than that (and that's were Marcus or someone else who really knows what they're talking about can jump in with a more informed point of view).

    EDIT: I think just invoking Occam's Razor might have saved me a few words up there.
  4. Oct 8, 2011 #3
    Please define this.
  5. Oct 8, 2011 #4


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    Not sure it matters. It's perfectly logical to argue that the sun blew up 5 minutes ago but we just don't know about it yet (and won't for another 3 minutes)
  6. Oct 8, 2011 #5


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    It isn't fair to single me out, or any one person, to ask this kind of question. It is a general question in the philosophy of science which plenty of people are as well or better prepared to answer than I am.

    The mods may erase this thread, or lock it, or move it to philosophy. The question about the constant uncertainty (but practical reliability) of scientific knowledge is not limited to cosmology. But cosmology provides a very clear example of it.

    Science is never certain, and is always being probed by scientists. Science is based on doubt and awareness of ignorance.

    THE REASON IT IS RELIABLE IS simply because it is the best we have so far. The reason it is the best we have so far is that the cultural tradition is to recognize how much you don't know and recognize the uncertainty and always test. Look for discrepancies where the math model does not fit the data. Where there is a misfit, keep trying to improve the model.

    This applies to all science but I am thinking especially of all mathematical science where the knowledge is not sentences in English but instead is a mathematical model which has been fit to data. The model is used to make predictions of future observations.
    E.g. what we will see, if the model is right, if we build this and this space telescope and measure that and that.

    You ask "how are scientists certain they know what is happening where nobody can see?"
    Cosmologists are very clear that they do NOT know. There could be a supernova explosion happening in Andromeda galaxy today and we would not know for a million years. Astronomers are very clear about limits to knowledge like that.

    Did anyone say they know for certain what is going on where they can't see? All you ever have is a mathematical model and you can explain to people (if they want to learn) what that model says. It's always understood the model could be wrong or have limited applicability. Our models are simply the best we have so far---those which have survived the most rigorous testing---and they are under constant scrutiny.
  7. Oct 9, 2011 #6


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    Lets assume that there is an intelliegent life out say 10b light years away looking in our direction. Someone there could be asking the same question - what is going on there right NOW? If you could communicate instantly, which you can't, but since you are living in the Here and Now, you know what is going on - you are living it.

    And if it is true that the universe is the same in every direction, you looking out can say that what is happening out there now is the same as what is happening here now.

    Please try to remember that telescopes look into the past, as you have stated - ie Long ago.

    But the following is probably asked by a lot of people:
    I guess we will find out in 13b years the answer to that question, and whether our model is correct.
    Last edited: Oct 9, 2011
  8. Oct 9, 2011 #7
    This is true, but I was aiming at the fact that synchronization over closed world lines is in not possible in a general curved space-time.
  9. Oct 9, 2011 #8
    You ask "how are scientists certain they know what is happening where nobody can see?"
    Cosmologists are very clear that they do NOT know.
    ...Did anyone say they know for certain what is going on where they can't see? All you ever have is a mathematical model and you can explain to people (if they want to learn) what that model says. It's always understood the model could be wrong or have limited applicability.[/QUOTE]


    First - my sincere apologies for an unbecomingly beseeching way of my question provoked by having been disregarded and unanswered many times by various physicists and philosophers.

    Next - my most cordial thanks for your exhaustive explanation.

    Two events prompted me to raise this question again.

    One - an article in the New York Times about the recent discovery that the Universe's expansion is accelerating and by extension about new mysterious forms of matter and energy.

    Another - a man from Jehovah Witnesses came to my door explaining that there do exist myriads of Spirits (God, Satan, billions of Angels, Demons etc.) that are invisible and undetectable because they are made from a different matter than we humans and everything around and that they are wielding unbelievably enormous energy of a quite different type than what we are accustomed to.

    To substantiate his preaching the man could offer only his unshakable Faith in the truth of his Bible based deductions.

    There was nothing of the Faith in the truth of Astronomy based deductions in the Times article.

    But as I understand from your explanation some, if only a grain, of Faith, not much unlike that of the Witnesses man, was there in the article, and I wish that the hypothesis-only aspects of these new discoveries be made clearer to the Laymen public.
  10. Oct 15, 2011 #9
    I love Uta-napishtim from Gilgamesh book :D (sry completely unrelated :D )
  11. Oct 15, 2011 #10


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    Gilgamesh is an exciting and fun book.What translation did you read? My favorite by far is the translation into English by David Ferry.

    Ut-Napishtim is, of course, the Noah prototype---the Ark builder. He gets tipped off by, if I remember right, a goddess----and learns that one of the other gods is going to drown everybody. He is not my favorite character. I like Enkidu best, the wildman who becomes a friend and companion to the hero Gilgamesh.

    The translator David Ferry seems to me to have a special sympathy with the material and is able to discover nuance, even humor, a human touch----subtle things another translator might not have noticed. As epics go---well, it is my kind of epic. I feel closer to Gilgamesh than I do to, for example, Homer's Iliad.
    Last edited: Oct 15, 2011
  12. Oct 15, 2011 #11
    Omgggg I love Enkidu too :D The way I see it is that he represents human evolution from cavemen, more monkey-like types of humans to civilized humans. I am not expert on evolution/early humans, but I think its possible that maybe humans around the time of Gilgamesh "remembered" their earlier origins as more hunter-gatherer types of humans, either through oral histories, cave pictures, or something..I mean Enkidu had no language, clothes, religion, was all hairy, and lived with animals..perfect caveman lol.

    And I like Uta Napishtim because I am jealous he gets to live forever and has his own cool island :D
    And I read the Andrew George translation, which is the newest one I think and incorporates all of the fragments of Gilgamesh found to date.
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