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The origin of time?

  1. Jun 1, 2013 #1
    As per current theory's we know that time did begin with the big bang, what before then and does big bang highlight the explosion or the dense ball which was everything (universe.)
  2. jcsd
  3. Jun 1, 2013 #2


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    Yes, that is one theory but not the only one so we do NOT "know" that, we take it as a part of one theory of how the universe works (the "Big Bang Theory")

    The big bang was NOT an explosion and there was no "ball".

    The "Big Bang Theory" is a description of how the Universe has acted since one Plank time after the singularity, from an incredibly hot and incredibly dense plasma of energy to what it is today.
  4. Jun 1, 2013 #3

    Simon Bridge

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    There is no "before" for time because the concept of "before" requires time.
    The "big bang", despite the name, should not be thought of as an explosion of anything.
    The name is sort-of a metaphore.

    A good start for this sort of question would be one of Hawkins lectures:
    ... gives you a better idea what you are asking about.
  5. Jun 1, 2013 #4

    Thanks. But as bigbang is the start of every thing ,is it right to assume that time is proportional(directly or inversly) to some quantity at that instant and why does cosmological time and thermodynamic time point in the same direction but why not physiological time it has 2 directions past and future.
    Last edited: Jun 1, 2013
  6. Jun 1, 2013 #5
    Our main evidence for the big bang is red shift. E.g if a fire engine is travelling towards us than the frequency is high and the pitch is high.
  7. Jun 1, 2013 #6


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    What you described is the classical Doppler shift which certainly doesn't explain the big bang in any way; it is a result that appears due to Galilean relativity (at near light speeds we have relativistic Doppler effects as well). The only thing remotely close to what you described is the cosmological redshift effect which helps support the idea of an expanding universe.
  8. Jun 1, 2013 #7
    by looking at the red shift of a large number of stars we can establish that they are moving away from us. However, other stars move away from each other so we cant tell exactly where the universe began. There are the possible ways that the universe could continue. Theory 1 the universe could expand forever. Theory 2 the universe could eventually stop expanding. Theory 3 the universe would expand until a certain point and the collide.
  9. Jun 1, 2013 #8


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    THERE IS NO "WHERE" to the beginning of the universe.

    I'm sure you meant "contract" not "collide"
  10. Jun 1, 2013 #9
    Some religious views of the origins of the universe contradict science and so for such views their is no real evidence. Notice I said some I am however aware that there is one religion which holds a scientific view of the origins of the universe
  11. Jun 1, 2013 #10
    sorry I meant contract
  12. Jun 1, 2013 #11
    nobody really knows...but increasing entropy seems to set a direction for time flow. However our mathematical models treat future and past equally. Einstein seemed to think our human perceptions of time had to be completely abandoned.

    See these two different views from well known physicists:

    On the reality of time and the evolution of laws

    Speaker(s): Lee Smolin

    "Forget time"
    Authors: Carlo Rovelli
    (Submitted on 23 Mar 2009 (v1), last revised 27 Mar 2009 (this version, v3))


    Einstein discovered that spacetime is not a fixed background, as it was assumed in special relativistic physics, but rather a dynamical field. A changing gravitational curvature as when a planet passes by, changes the passage of time according to a distant observer. This means proper time along a curved inertial world line [a path in spacetime] varies from point to point for a distant observer, since the gravity changes.

    Proper time along a worldline IS an observable but does not 'tick at a steady pace',because as the worldine is traversed, as you move through spacetime, the spacetime background is, in general changing....the spacetime background is dynamic, so time proceeds 'erratically'...at an uneven paceā€¦.. as viewed by others. In SR, different inertial observers see distant time pass at different rates relative to their own time, but the ticks are at a fixed pace.
    So the concept of time is weakened somewhat in GR since the pace of ticks varies.
  13. Jun 1, 2013 #12
    We can't even get everyone to agree that time exists. We can observe and measure its effects but have no understanding of its cause. If time is motion or distance, then time most likely started with the Big Bang or very shortly thereafter. If time can be separate from space then it could have existed before the Big Bang but had nothing to measure against. Cosmology deals with space-time as a single entity and uses physics to explain what we see and predict what we have yet to see. If you try to view one without the other (space without time or vice versa) everything breaks down and stops working based on what we currently view as the best answers.
  14. Jun 1, 2013 #13
    But then ,will entropy decrease result in time flowing backwards. If its true then one can be sure that inside black holes time runs backward's
  15. Jun 1, 2013 #14
    By the evidences currently available all objects in the universe are moving away from us, doesnt this mean that a point of origin must exist.
  16. Jun 1, 2013 #15


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    Emphatically not. You misunderstand the evidence. ALL things in the universe are moving away from each other exactly as all things are moving away from us. There IS no privileged point of view ("center"). Google "Cosmological Principle"

    If you had it right then WE would be at the point of origin of the universe (as of course would every other point in the universe)

    Also, you might find it informative to read what is at the URL in my signature.
    Last edited: Jun 1, 2013
  17. Jun 1, 2013 #16
    No it most certainly does not.

    Expansion is the same everywhere except where other forces are stronger such as large scale structures and gravity.
  18. Jun 1, 2013 #17


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    My bold... that's getting pretty close to the definition of everywhere, isn't it?


  19. Jun 1, 2013 #18


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    It had not been my intent to be "getting pretty close to everywhere" but rather to express that it IS everywhere.
  20. Jun 1, 2013 #19


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    Aah, yes... fixed!

  21. Jun 1, 2013 #20

    Simon Bridge

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    A lot of these questions are covered in the lecture I gave you - post #2 - did you follow the link?

    The first question is handled in the link I gave you, as for the second, there is no reason to suppose that physiological time in our bodies is any different from the "time" we measure with any other kind of clock.

    Our perception of time, on the other hand, is something that happens in our minds. It's relation to the physical world would, therefore, be a mind-body problem. Nobody has solved that one yet.

    But if you mean "why do we remember the past and not the future?"
    That can be understood in two stages:
    1. remember(!) that we call the stuff we remember "the past" because we remember it - it's the definition of "the past". (Lets not get bogged down in ideas about historical past and True past events and false memories etc please? You know what I mean - thanks.)
    2. our memories are not magic - they must be laid down by some physical process. To be persistent, which they must be to be called "memory", the process must be irreversible. Thus "memory" must be one way ... irreversible processes go in the direction of increased entropy - therefore, so does our memory of the order of events.

    Hawking actually covered this in "A Brief History of Time" quite a while ago and many others have written on it since (and before).

    We can decrease entropy locally, and that does not result in backwards flowing time.
    But you should be careful what you mean by "backwards" and "forwards" in the context of time. These are directions relative to something ... what would time be moving back or forth with respect to?

    We see time flowing in the same direction as the increase in total entropy.
    When local entropy decreases, it does so against the flow of total entropy change.
    If total entropy were to decrease - would we notice?
    For us to notice we'd have to see our clocks turn backwards ... which would mean that our local entropy (in the mechanism that lays down our memories) would be running the opposite way to the total entropy. So which is going backwards, time, or us?

    Dan Dennet talks about how memory works in his provocative "Consciousness Explained" - his recent TED talks are largely about perception. They will help you here I think.

    Inside a black hole there is no reason to suppose time "runs backwards" there either - though that is a whole different kettle of piranhas.
    My favorite link for what happens inside a black hole - as near we can make out - is:
    I think this goes beyond the concepts you are wresting with though.

    As the others have said: no. It is a very common misconception that the Big Bang is the Universe exploding into being from some point - see Disney's Fantasia for a typical illustration.

    You should read the link in Phinds' sig.

    Note: the ideas you are trying to work through are very big - there is no way anyone can provide complete answers in these forums. That is why we give you links and pointers for further reading. Do go read them.
    Last edited: Jun 1, 2013
  22. Jun 2, 2013 #21
    Thanks and As we all know that universe is defined as every thing we know then how can one think of possibility of existence of parallel universe's . This one doesn't cope up with the definition because as per definition parallel universe must also be included in the known universe.
    Last edited: Jun 2, 2013
  23. Jun 3, 2013 #22
    All objects are not movig away from each other, gravitationally bound objects are not doing so. The Andromeda galaxy is on a collision course with our galaxy. They are not moving away from each other. Distant galaxies are moving away from each other and this is what the epxnasion of the universe means. If the bgi rip were to hapen then your scenario would be correct. but we do not know that the big rip will happen. Current data doesn't support it, but until we understand dark energy better than we can say its a possibility.
  24. Jun 3, 2013 #23

    Simon Bridge

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    A parallel Universe may be one which might have been but wasn't without violating the idea that the Universe is everything there is.
    Since "Universe" is a label we are free to come up with other uses for it - words are our tools not our masters. Certainly it is not useful to define the Universe as "everything we know" - for surely the Universe also contains many things we have yet to discover?

    But that is a different topic... and it does not appear to follow on from what I wrote or from the original topic. You should ask it in a different thread perhaps?

    Have you taken in what people are trying to tell you?
    Have you read the links provided?
  25. Jun 3, 2013 #24
    Please explain me about big crunch. Big crunch does state a single point where all of the universe will be one.(Please correct me if i am wrong.)
  26. Jun 3, 2013 #25


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    You are wrong. The "big crunch" scenario says the universe, that started off as an incredibly hot dense plasma of possibly infinite extent and which has since expanded enormously, will contract back to the original incredibly hot dense plasma of possibly infinite extent. There is no "point" involved in either the beginning or the end of the big crunch.
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