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Thread: How is the age of the universe calculated???

  1. #1 How is the age of the universe calculated??? 
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    How can we say that the universe was created with a bang, 13.7 billion years ago,
    when there is no center to the universe?

    I know (cos I read it) now that every galaxy is moving away from every other galaxy.
    However, I can't visualize this.

    Suppose these galaxies A, B, and C are in line with each other like this
    A .............B................................C

    So, if A is moving at velocity X towards B, and B is also moving at velocity Y towards C
    , then we can see B moving away from us ( A) at (y-x).

    Also, if C is moving away from A at velocity Z, then we can see C moving away from us at (z-x)??

    So, the velocities are not equal??? So, how do they say everything is moving away from each other at same speed?

    For example, if you bake a load of bread with raisins inside, after baking the
    load is bigger and the raisins inside have moved apart from each other?
    But, is this a good example??

    How do we say the universe started with big bang when we can't find a center and
    every thing is moving away from everything else at the same speed?


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  3. #2  
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    So, how do they say everything is moving away from each other at same speed?
    They don't. All non gravitationally bound objects are receding from each other, and the further apart they are, the faster they are receding from each other.


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    Quote Originally Posted by rohandesilva View Post
    How can we say that the universe was created with a bang, 13.7 billion years ago,
    when there is no center to the universe?

    I know (cos I read it) now that every galaxy is moving away from every other galaxy.
    However, I can't visualize this.

    Suppose these galaxies A, B, and C are in line with each other like this
    A .............B................................C

    So, if A is moving at velocity X towards B, and B is also moving at velocity Y towards C
    , then we can see B moving away from us ( A) at (y-x).

    Also, if C is moving away from A at velocity Z, then we can see C moving away from us at (z-x)??

    So, the velocities are not equal??? So, how do they say everything is moving away from each other at same speed?

    For example, if you bake a load of bread with raisins inside, after baking the
    load is bigger and the raisins inside have moved apart from each other?
    But, is this a good example??

    How do we say the universe started with big bang when we can't find a center and
    every thing is moving away from everything else at the same speed?
    Think of a balloon. Blow it up a little. Now paint stars on it.
    If you blow it up more you will see all stars moving away from each other.
    The two dimensional space models what is happening in our space.
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    1/hubble constant = hubble time = 13.75 billion years
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  6. #5  
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    rohandesilva, things are not all moving at the same speed, as Alex pointed out. And yes, the bread/raisin analogy is a good one. In fact, inside the bread, the raisins are not moving at the same speed. How fast they move will depend on many variables including how much heat is affecting the material around the raisin, how that material is affected by the heat (for example, if there is a little clump of unmixed flour, that will not expand like the material around it), etc. The baking of bread is an extremely complex system, and we can't account for every particle of dough and raisin, but we can tell what is happening in a general sense--the raisins are moving away from each other as the dough rises.
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    Expansion doesn't have a center due to the same reason a surface of ballon doesn't have a center! If you live on a surface of a ballon: you won't see a center (you can walk on the surface forever and find no end). You only see a center when you are OUTSIDE the surface looking at the ballon on your hand.
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    With a calculator.
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  9. #8  
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    Quote Originally Posted by rohandesilva View Post
    How do we say the universe started with big bang when we can't find a center and
    every thing is moving away from everything else at the same speed?
    There's a logically false premise in your question. The definition of the universe is "everything that exists". The big bang is an hypothesis, if we make the working assumption that it is accurate then the logical conclusion is that the universe transformed fully or partially (we can't know of other dimensions, they are logically possible but not scientifically reachable) from something else to how it is observed to exist now.

    Logically it is impossible that there was a big bang that "created" the universe.

    edit:
    As a side note, another commonly used logical fallacy is to hypothesize about multiple universes.
    Last edited by grandi; September 23rd, 2012 at 07:39 AM.
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    Quote Originally Posted by grandi View Post
    Quote Originally Posted by rohandesilva View Post
    How do we say the universe started with big bang when we can't find a center and
    every thing is moving away from everything else at the same speed?
    There's a logically false premise in your question. The definition of the universe is "everything that exists". The big bang is an hypothesis, if we make the working assumption that it is accurate then the logical conclusion is that the universe transformed fully or partially (we can't know of other dimensions, they are logically possible but not scientifically reachable) from something else to how it is observed to exist now.

    Logically it is impossible that there was a big bang that "created" the universe.

    edit:
    As a side note, another commonly used logical fallacy is to hypothesize about multiple universes.
    Speaking about logical fallacies is too hasty here.
    How do we know other dimensions cannot be detected were they to exist?
    And the definition of the universe as "everything that exists" is presumptuous!
    We are in a universe but we dont know if this universe is connected with everything that exists.
    The definition is old and originates from a simplistic time when there was a god
    able to create our possibly small and rather insignificant universe.
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    Quote Originally Posted by grandi View Post
    [Logically it is impossible that there was a big bang that "created" the universe.
    Please explain why you know it to be impossible for the universe to have been created out of nothing. While creation ab nihilo is thought to be impossible in the universe, there is no compelling reason to be certain that the same rules apply to nothing. If you know of such rules please share them.

    Quote Originally Posted by grandi View Post
    As a side note, another commonly used logical fallacy is to hypothesize about multiple universes.
    This is not a logical fallacy, but an example of lexical evolution in a scientific context. (Please note a prior expression of this development: when galaxies were first suspected to be objects outside our galaxy they were referred to as island universes. I think this usage may still have been current in popular language into the 1950s.)
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    Quote Originally Posted by John Galt View Post
    Quote Originally Posted by grandi View Post
    [Logically it is impossible that there was a big bang that "created" the universe.
    Please explain why you know it to be impossible for the universe to have been created out of nothing. While creation ab nihilo is thought to be impossible in the universe, there is no compelling reason to be certain that the same rules apply to nothing. If you know of such rules please share them.
    In scientific terms universe is defined as everything that exists. If you say that a big bang existed before the universe existed then you by default are saying:
    Something existed before everything began to exist, that is a pure and absolute logical fallacy within the actual strict definitions of those terms.

    Quote Originally Posted by John Galt View Post
    Quote Originally Posted by grandi View Post
    As a side note, another commonly used logical fallacy is to hypothesize about multiple universes.
    This is not a logical fallacy, but an example of lexical evolution in a scientific context. (Please note a prior expression of this development: when galaxies were first suspected to be objects outside our galaxy they were referred to as island universes. I think this usage may still have been current in popular language into the 1950s.)
    If you use the term universe which is within science defined as everything that exists then it is a logical fallacy. When speaking in terms of religions and different myths then all sorts of unobservable magical beings apparently exist. Is there a rational explanation as to why something that is thought to exist should be excluded from the general term including everything that exists?
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  13. #12  
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    Quote Originally Posted by grandi View Post
    If you use the term universe which is within science defined as everything that exists then it is a logical fallacy.
    Not if the definition changes. The original meaning of "atom" was indivisible. Are suggesting that nuclear fission is impossible because of etymology?

    Never forget what Saussure said about words.
    ei incumbit probatio qui dicit, non qui negat
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    Quote Originally Posted by Strange View Post
    Quote Originally Posted by grandi View Post
    If you use the term universe which is within science defined as everything that exists then it is a logical fallacy.
    Not if the definition changes. The original meaning of "atom" was indivisible. Are suggesting that nuclear fission is impossible because of etymology?

    Never forget what Saussure said about words.
    In regards to science, do you consider "the universe" a subset of everything that naturally exists?
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    Quote Originally Posted by grandi View Post
    In scientific terms universe is defined as everything that exists. If you say that a big bang existed before the universe existed then you by default are saying:
    Something existed before everything began to exist, that is a pure and absolute logical fallacy within the actual strict definitions of those terms.
    In scientific terms, this only applies to what is known as the OBSERVABLE universe.

    Quote Originally Posted by grandi View Post
    If you use the term universe which is within science defined as everything that exists then it is a logical fallacy.
    Your man of straw is based on an obsolete definition. In scientific terms, astronomy and cosmology only deal with the observable universe.

    The current mainstream model in cosmology, the Lambda-Cold Dark Matter concordance model, deals ONLY with the observable universe and that is all we are referring to in this thread.
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    Quote Originally Posted by SpeedFreek View Post
    Quote Originally Posted by grandi View Post
    In scientific terms universe is defined as everything that exists. If you say that a big bang existed before the universe existed then you by default are saying:
    Something existed before everything began to exist, that is a pure and absolute logical fallacy within the actual strict definitions of those terms.
    In scientific terms, this only applies to what is known as the OBSERVABLE universe.

    Quote Originally Posted by grandi View Post
    If you use the term universe which is within science defined as everything that exists then it is a logical fallacy.
    Your man of straw is based on an obsolete definition. In scientific terms, astronomy and cosmology only deal with the observable universe.

    The current mainstream model in cosmology, the Lambda-Cold Dark Matter concordance model, deals ONLY with the observable universe and that is all we are referring to in this thread.
    Observable universe does not equate to "everything that can be observed now". It refers to everything that is ever possible to be observed, now or any time in the future, here on anywhere else. Parts of the universe may be beyond light's capability to reach us so we can never observe them, it doesn't mean that those parts are no longer part of the universe.

    Science makes progress and new discoveries are made constantly, it doesn't mean that the term universe constantly changes its meaning.
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    We know that. So, what is your point then?
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  18. #17  
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    Quote Originally Posted by grandi View Post
    In regards to science, do you consider "the universe" a subset of everything that naturally exists?
    If any of the various "multiple universe" hypotheses were validated then there would seem to be two choices:

    1. Use the word "universe" to refer to the totality of all those and use a new word (miniverse? subverse?) for the individual formerly-known-as-universes within that.

    2. Create a new word for the totality of all these universes (e.g. multiverse).

    I suspect, based on usage so far, that it would go in the direction of 2.

    Note that the meaning of words defined by usage not etymology.
    ei incumbit probatio qui dicit, non qui negat
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    Quote Originally Posted by SpeedFreek View Post
    We know that. So, what is your point then?
    Now you seemed to make a complete turnaround. The point was to clear up the few technical matters.
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    Quote Originally Posted by Strange View Post
    Quote Originally Posted by grandi View Post
    In regards to science, do you consider "the universe" a subset of everything that naturally exists?
    If any of the various "multiple universe" hypotheses were validated then there would seem to be two choices:

    1. Use the word "universe" to refer to the totality of all those and use a new word (miniverse? subverse?) for the individual formerly-known-as-universes within that.

    2. Create a new word for the totality of all these universes (e.g. multiverse).

    I suspect, based on usage so far, that it would go in the direction of 2.

    Note that the meaning of words defined by usage not etymology.
    Language is only a means to relay understanding. I suppose the general population will decide in an evolution like manner how the terms are defined. The negative side effect of changing the meaning of terms is though that it creates unnecessary confusion and unintentional straw man arguments. My preference would be to create a new word for a new concept. The uncontrollable evolution of languages will dictate however.
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    Quote Originally Posted by grandi View Post
    The negative side effect of changing the meaning of terms is though that it creates unnecessary confusion and unintentional straw man arguments.
    Indeed. In any such transition, there is a need for people to be especially careful to define what they mean, perhaps by using redundant information.
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    Quote Originally Posted by grandi View Post
    Quote Originally Posted by SpeedFreek View Post
    We know that. So, what is your point then?
    Now you seemed to make a complete turnaround. The point was to clear up the few technical matters.
    What on earth are you talking about?

    The OP was asking about the Big-Bang, which is the apparent beginning of our (observable) universe, and was asking how we calculate the age of the (observable) universe. You came along muddying the waters with your perceived logical fallacies in the OP, trying to discuss a far wider question (whether the Big-Bang and the universe that came from it came from something else).

    Surely you aren't just referring to the fact that we cannot put an age on whatever it is that might have caused our universe? We are referring here to the time since the Big-Bang, after all.

    So, what is your point in nitpicking the OP, exactly?
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    Actually, the OP's question (which seems to have been forgotten slightly) is ambiguous.

    It could be a question about creation: "How can we say that the universe was created (with a bang, 13.7 billion years ago)" in which case the answer is, we don't know.

    Or it could be a question about time since the big bang: "How can we say ... [there was] a bang, 13.7 billion years ago". In which case, the answer has been given: trace the observed expansion back in time.
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    Good point. My apologies.
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    Quote Originally Posted by rohandesilva View Post
    How can we say that the universe was created with a bang, 13.7 billion years ago,
    when there is no center to the universe?
    What we know is that any center of the universe is not within the universe!
    Which "hints" at an outside of our universe
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    grandi, despite the echanges above, where light seems to be slowly dawning on you, I'm still not sure you have got it.

    The term universe has changed over time. You have not commented on the fact that in the 1920s for sure the phrase "island universe" was used in the scientific community. Do you want to go descerate the graves of those astronomers for being wrong! Of course not. Similarily today it is acceptable to talk about multiple universes and parallel universes. It's not a big deal, unless you are opposed to change. And, as Strange points out, when change is ongoing we need to be very careful to make clear what definition we are using. But that's good practice at any time.
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    Quote Originally Posted by John Galt View Post
    grandi, despite the echanges above, where light seems to be slowly dawning on you, I'm still not sure you have got it.

    The term universe has changed over time. You have not commented on the fact that in the 1920s for sure the phrase "island universe" was used in the scientific community. Do you want to go descerate the graves of those astronomers for being wrong! Of course not. Similarily today it is acceptable to talk about multiple universes and parallel universes. It's not a big deal, unless you are opposed to change. And, as Strange points out, when change is ongoing we need to be very careful to make clear what definition we are using. But that's good practice at any time.
    I do understand what you mean and I did comment on the evolution of languages. I guess we have to live with it. Although if everyone used the term universe clearly as a description for everything that exists it would make communication around this "hot topic" easier. Multiple universes and parallel universes downgrade the term universe significantly. It would seem more logical to talk about the universe consisting of multiple sub-universes or dimensional aspects.

    I did laugh at the comment about desecrating astronomers' graves, that was funny. Hopefully I offended no-one
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    I always liked that idea of the word universe; that it should encompass all things, everywhere. If that is not quite what astronomy means by the term, then I should like a new term I can bandy about. I'm going to try a few out and see how well they work. Hm. I think I'll start with... omegaplex! Wait that's not already a thing is it? Omegaplex?
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    Quote Originally Posted by JoshuaL View Post
    I always liked that idea of the word universe; that it should encompass all things, everywhere. If that is not quite what astronomy means by the term, then I should like a new term I can bandy about. I'm going to try a few out and see how well they work. Hm. I think I'll start with... omegaplex! Wait that's not already a thing is it? Omegaplex?
    Well...

    OmegaPlex«

    This is what comes up when you google "omegaplex".

    As for the universe, I too would be interested in a solid definition. It does not appear that there has been a conclusion.
    Last edited by guymillion; September 23rd, 2012 at 07:19 PM.
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    Ive always wondered why do people try to find the age of the universe and prove wether god exists when we dont even have the technology to leave our solar system, terraform planets in our solar system or even to easily leave our own tiny planet? it kinda seems like a waste of energy to me if we found out the universe would end in a week we couldnt do anything about and if other universes exist do you think we would ever travel there in the next 1000 years? It just seems we should solve todays problems today.
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    In another thread a member queried the value of seeking to explore Mars with robots, rather than solving our immediate problems. I pointed out that if the same objection to blue sky research had been used to shut down research on micropalaeontology then correlation techniques that facilitate the discovery of oil reservoirs would never have been developed; less oil would have been discovered; fewer oil based fertilisers would have been available for the Green Revolution; and there would therefore be more starving people in the world.

    A second, quite separate argument, is that asking and answering questions is what we do. It's what makes us human.
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    But i think exploring mars i a great idea i think we should be doing far far more of that because to me that seems practical. The more we learn about planets in our solar system the closer we are to terraforming them and learning more about particles is a great idea because it allow us to have a better understanding of how particles interact and how to make new materials etc. The point was why study something that is currently imposible for us to really prove like the exsistence of god and age of the universe etc.
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    And my point is that we have absolutely no idea where a particular piece of research will lead. IF we restrict ourselves to the immediately practical we damage our long term prospects. In the field of economics it is just such short term thinking which has screwed up our economy.
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    No what would have been immediately practical would have been to avoid the economic mess altogether to have seen what was coming and to have planned for it to have technologies invented already to solve future problems. One such case is wether we could stop an asteroid form hitting the planet i certainly dont think so. Your point is valid though you cannot know where one piece of research will lead. But where has at least 2000 years of research into proving the existence of god gotten us? As for the age of the universe we only have one perspective currently i certainly dont think that is enough for accuracy i think we will need at least four solar systems before we even come close to a correct awnser. I just think there is far too many variables to take into consideration at the moment.
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    Quote Originally Posted by fiveworlds View Post
    No what would have been immediately practical would have been to avoid the economic mess altogether to have seen what was coming and to have planned for it to have technologies invented already to solve future problems. One such case is wether we could stop an asteroid form hitting the planet i certainly dont think so. Your point is valid though you cannot know where one piece of research will lead. But where has at least 2000 years of research into proving the existence of god gotten us? As for the age of the universe we only have one perspective currently i certainly dont think that is enough for accuracy i think we will need at least four solar systems before we even come close to a correct awnser. I just think there is far too many variables to take into consideration at the moment.
    Excuse what may seem like negative criticism, but your post has several flaws.
    1. There is little doubt that we could stop an asteroid strike. The only issue is whether we would have sufficient time to implement the solution.
    2. Science does not attempt to prove the existence of God. Science pursues a path of methodological naturalism, so God does not enter into it.
    3. The age of the universe has been explored from at least two major perspectives: Big Bang and Steady State. The balance of evidence supports the former and disproves the latter.
    4. Solar systems are not used to determine the age of the universe, therefore your wish for us to have more than four to consider is meaningless.
    5. Even if it were remotely valid we now have many hundreds of solar systems available for study, so your reservation is demolished.
    6. Science is largely indifferent to what you think, since you appear to be inadequately informed on the subject.
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    The solar systems point is merely the point of perspective. Secondly how many of these hundreds of solar systems have we been to in order to establish wether we really get a clear picture of our universe to know beyond all reasonable doubt that our view of universe is even remotly correct. Thirdly timing was my point on the asteroid strike. Fouthly science is not a thing and therefore doesnt have feelings. Fifthly science is merely a study of everthing therefore everybody who asks questions is a scientist. Sixtly i prefer big bang theory and finally you seem very easily annoyed over something insignificant.
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    Quote Originally Posted by fiveworlds View Post
    The solar systems point is merely the point of perspective. Secondly how many of these hundreds of solar systems have we been to in order to establish wether we really get a clear picture of our universe to know beyond all reasonable doubt that our view of universe is even remotly correct. Thirdly timing was my point on the asteroid strike. Fouthly science is not a thing and therefore doesnt have feelings. Fifthly science is merely a study of everthing therefore everybody who asks questions is a scientist. Sixtly i prefer big bang theory and finally you seem very easily annoyed over something insignificant.
    Let me take the last point first. I am not annoyed. Your are posting statements as if they were facts when they are incorrect. Left uncorrected casual reader might go away from this thread badly misinformed. Do you wish that to happen? Are you comfortable about posting incorrect information? I welcome corrections to any errors I make, but I also take considerable care to hold those errors to a minimum.

    You continue to tie the study of solar systems to the age of the universe. The age of the universe has been determined by observation of distant galaxies, not by observation of this, or any other, solar system. Considering solar systems in relation to the age of the universe does not give us a relevant different perspective. It happens, not surprisingly, that the age determined for the solar system is consistent with the age of the universe, but that is a trivial observation.

    We haven't been to Mars, yet we have mapped its surface in more detail than we have the surface of the Earth.

    What on Earth does your comment about science not having feelings have to do with anything. And yes, science is a thing, it is a method of acquiring and testing information. This does not in any way detract from my initial point: attempts to prove or disprove god have absolutely nothing to do with science.

    Now for the big one: Science is not the study of everything, nor is it just about asking questions. Science deliberately restricts itself to the study of natural phenomena and it does so in a highly formalised way. Just asking questions does not constitute science. How the questions are asked and the answers validated determines whether or not it is science.

    Fiveworlds, the last thing I wish to do is discourage you from participation in the forum. You and your thoughts are most welcome here, but when you make posts filled with sloppy thinking, I - or someone else will correct you. I hope you will do the same to my posts if you see an error.
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    Quote Originally Posted by fiveworlds View Post
    The point was why study something that is currently imposible for us to really prove like the exsistence of god and age of the universe etc.
    Why do you persist in saying we do not know (roughly) the age of the universe?
    Now youve said it TWICE!

    And here is a proof of the existence of god:
    Definition: x is god if x is a cause of existense.
    1 There is existence (check for yourself)
    2 if x exists then x has a cause (scientific principle)
    3 Therefore god exists!

    But I agree with you that "we" should hurry up with the colonization of space.
    Its irresponsible not being able to prevent the extinction of mankind by asteroids or comets.
    Looking at the statistics we should be dead by now!
    Last edited by sigurdW; September 24th, 2012 at 06:16 AM.
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    sigurdW, please don't start with that nonsense again! You have had your time to try and convince. You failed miserably. Leave it at that.
    Disclaimer: I do not declare myself to be an expert on ANY subject. If I state something as fact that is obviously wrong, please don't hesitate to correct me. I welcome such corrections in an attempt to be as truthful and accurate as possible.

    "Gullibility kills" - Carl Sagan
    "All people know the same truth. Our lives consist of how we chose to distort it." - Harry Block
    "It is the mark of an educated mind to be able to entertain a thought without accepting it." - Aristotle
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    Quote Originally Posted by KALSTER View Post
    sigurdW, please don't start with that nonsense again! You have had your time to try and convince. You failed miserably. Leave it at that.
    He was twice saying there is no proof of the the existence of god.
    I created one. He must have missed it. So I show him.

    And you, Kalster:

    You know the correct definition of god?
    Be scientific then and tell fivewords
    that whats wrong with the proof
    is that it does NOT conform to the Bible!
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    I said enough.
    Disclaimer: I do not declare myself to be an expert on ANY subject. If I state something as fact that is obviously wrong, please don't hesitate to correct me. I welcome such corrections in an attempt to be as truthful and accurate as possible.

    "Gullibility kills" - Carl Sagan
    "All people know the same truth. Our lives consist of how we chose to distort it." - Harry Block
    "It is the mark of an educated mind to be able to entertain a thought without accepting it." - Aristotle
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    Quote Originally Posted by JoshuaL View Post
    I always liked that idea of the word universe; that it should encompass all things, everywhere. If that is not quite what astronomy means by the term, then I should like a new term I can bandy about. I'm going to try a few out and see how well they work. Hm. I think I'll start with... omegaplex! Wait that's not already a thing is it? Omegaplex?
    I like to think of the observable universe as the part of our local universe that we can see. I define the local universe as the one we live in regardless of how large it might be. I suspect our local universe is not all there is, but is a part of a much larger system or structure in which the events that created our local universe are natural and have happened before and will happen again and may be happening many times in parallel with our own local universe.

    I don't really care if I'm right or wrong, because I need the universe to be natural. Which it can't be if it's a one of a kind event never to be repeated again.
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    [QUOTE=arKane;354236]
    Quote Originally Posted by JoshuaL View Post
    I need the universe to be natural. Which it can't be if it's a one of a kind event never to be repeated again.
    Good point! I agree.
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    Quote Originally Posted by rohandesilva View Post
    How is the age of the universe calculated??? How can we say that the universe was created with a bang, 13.7 billion years ago when there is no center to the universe?
    The age of the universe is calculated according to the Big Bang model. Other cosmological models may calculate a different age for the universe, or just a minimum age, and some propose an infinite age. The cosmological equations of General Relativity allow for a center of a finite universe, but the present consensus is that the universe is finite but curves around upon itself without center or edges.

    What was once perceived as the Hubble constant expansion rate of the universe, now can be referred to as the average expansion rate, considering the dark energy hypothesis and accordingly changing expansion rates of the universe starting with the Inflation-hypothesis era. According to the Big Bang model, following the period of rapid inflation there was a slowing down deceleration period and now accordingly an accelerating period again beginning about 6 billion years ago. Since the Inflation period was accordingly a relatively very short period of time, if one uses the average expansion rate of the universe and follows it backward in time one accordingly will end up at a single point or small volume, presently estimated to be 13.75 billion years ago.

    Age of the universe - Wikipedia, the free encyclopedia

    I know (cos I read it) now that every galaxy is moving away from every other galaxy.
    However, I can't visualize this.

    Suppose these galaxies A, B, and C are in line with each other like this
    A .............B................................C

    So, if A is moving at velocity X towards B, and B is also moving at velocity Y towards C
    , then we can see B moving away from us ( A) at (y-x).

    Also, if C is moving away from A at velocity Z, then we can see C moving away from us at (z-x)??

    So, the velocities are not equal??? So, how do they say everything is moving away from each other at same speed?

    For example, if you bake a load of bread with raisins inside, after baking the
    load is bigger and the raisins inside have moved apart from each other?
    But, is this a good example??

    How do we say the universe started with big bang when we can't find a center and
    every thing is moving away from everything else at the same speed?
    The Big Bang model, via present interpretations of General Relativity, attributes the appearance of "galaxies moving away from each other" to the idea of the expansion of space. The idea is that there was originally one point, or small volume, that expanded into what we see today. The matter and energy accordingly was generally not moving while the spaces in between the whole, expanded. Although galaxies do have relative motion in that they often orbit each other in groups, clusters, and superclusters, they accordingly have no real motion away from each other as a whole.

    There are different versions of the Big Bang model, different Inflation models, different dark energy and dark matter proposals, but most versions of all of them generally agree on these points.
    Last edited by forrest noble; September 26th, 2012 at 12:17 PM.
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    Quote Originally Posted by JoshuaL View Post
    I always liked that idea of the word universe; that it should encompass all things, everywhere. If that is not quite what astronomy means by the term, then I should like a new term I can bandy about. I'm going to try a few out and see how well they work. Hm. I think I'll start with... omegaplex! Wait that's not already a thing is it? Omegaplex?
    Yeah, omegaplex has a different meaning. You don't want to use that.

    The term "universe" still has a definition similar to what you described.

    The universe is commonly defined as the totality of existence, including planets, stars, galaxies, the contents of intergalactic space, all matter and energy.

    So with the multi-verse ideas the definition of the universe would generally remain the same since another "universe" would be totally disconnected from this one by either, time, or dimensions in space and/or matter. If after its creation another hypothetical universe could ever interact with our own universe somehow in any way, then an extended definition of "universe" seemingly would be needed.

    As for now, "the various hypothetical universes within the multiverse hypothesis are sometimes called parallel universes."

    Therefore, it would seem that our definition can generally remain intact with maybe a small addendum.

    Such an extended new definition might be: The universe is the totality of all existence, including planets, stars, galaxies, the total contents of space, all matter, energy, space and time, within our own dimensional reality.

    And the definition of separate universes within a multi-verse might be: A universe is the totality of all existence, including planets, stars, galaxies, the total contents of space, including any and all matter, energy, space and time, within its own dimensional reality.

    But for all practical purposes I think the existing definition should not change. Generally speaking, the universe includes everything.
    Last edited by forrest noble; September 27th, 2012 at 09:59 AM.
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    Quote Originally Posted by grandi View Post
    Quote Originally Posted by John Galt View Post
    grandi, despite the echanges above, where light seems to be slowly dawning on you, I'm still not sure you have got it.

    The term universe has changed over time. You have not commented on the fact that in the 1920s for sure the phrase "island universe" was used in the scientific community. Do you want to go descerate the graves of those astronomers for being wrong! Of course not. Similarily today it is acceptable to talk about multiple universes and parallel universes. It's not a big deal, unless you are opposed to change. And, as Strange points out, when change is ongoing we need to be very careful to make clear what definition we are using. But that's good practice at any time.

    I do understand what you mean and I did comment on the evolution of languages. I guess we have to live with it. Although if everyone used the term universe clearly as a description for everything that exists it would make communication around this "hot topic" easier. Multiple universes and parallel universes downgrade the term universe significantly. It would seem more logical to talk about the universe consisting of multiple sub-universes or dimensional aspects.

    I did laugh at the comment about desecrating astronomers' graves, that was funny. Hopefully I offended no-one
    IMO, the use of the COSMOS would be more appropriate as an ultimate physical constant than a multiverse.
    From wiki
    In Mandarin Chinese, cosmos and universe are both translated as 宇宙 yuzhou, which literally translated means space-time (宇 yu = space + 宙 zhou = time).
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    Quote Originally Posted by forrest noble View Post
    The universe is commonly defined as the totality of existence, including planets, stars, galaxies, the contents of intergalactic space, all matter and energy.
    This is a direct quote from wikipedia. Remember to cite your sources.
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    Quote Originally Posted by guymillion View Post
    Quote Originally Posted by forrest noble View Post
    The universe is commonly defined as the totality of existence, including planets, stars, galaxies, the contents of intergalactic space, all matter and energy.
    This is a direct quote from wikipedia. Remember to cite your sources.
    Thanks, got it
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    The Age of the Universe is the distance from the local moment to the big bang.
    This I use to define simultaneity:

    If the age of the universe is the same in two events then the events are simultaneous!

    This definition conforms better to our intuition then the definition of simultaneity in Relativity.

    Also using this definition the relativistic definition need no longer be circular,
    since the age of the universe surely is the same for all incoming light rays within a point!

    Minor remarks:
    1 Since the age of the universe is not a "frame "in relativity (There is no universal frame remember?)
    then how can relativity theory apply to the aging of the universe? Is relativity in need of extension?

    2 There IS the question whether the AGING of the Universe is Equivalent to absolute time...
    Opponents will deny there is an absolute time without stopping to realise
    that they dont know what it is they deny the existence of!

    3 So here is my definition of Absolute Time:
    A clock shows Absolute Time if and only if it is unaffected by change in speed or gravitational effects.
    If it accelerates or decelerates in a frame then its internal speed is adjusted accordingly.
    This means it will stay synchronised with the frame its time was set in.

    4 Considering the universe as a clock, it shows absolute time according to the definition.
    Last edited by sigurdW; September 28th, 2012 at 09:55 AM.
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