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New objects in the heavens ?

  1. Aug 26, 2004 #1
    We can't see the whole universe but only a portion: the visible universe is the region from which light did have time to reach us (our past light cone).
    We are familiar with the quote that "there is much more universe out there, but its light did not yet have time to reach us".

    As time will pass, can we expect completely new objects to suddenly appear in the sky? I mean, are there objects whose light by now did not yet reach us but (let's say) by year 2500 their light will finally arrive to us so a new object will suddenly show up in our telescopes?

    Or is the visible horizon fixed so objects that are out of it will remain forever out of sight?

    And putting the question upside down, could the opposite happen?, an object which we can now see, could it due to motion or space expansion get too far so light from it would not reach us anymore? (visible objects suddenly disappearing from sight)
    Last edited by a moderator: Aug 27, 2004
  2. jcsd
  3. Aug 26, 2004 #2


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    In a question such as this, it is usefull to think in terms of "events", rather than objects. After all, the existence of an object is an event. With this in mind, the first question becomes easy to answer. For example, we have located some "stellar nurseries", in which we would see stars begin to form (we think), if we had time to wait around and watch. Chances are, some stars have already formed within these nebulae. To an observer near the stellar nursery, these stars already exist, but to us, they will not come into existence for many years (assuming the stellar nursery in question is many light-years away).
  4. Aug 27, 2004 #3
    Thanks Lurch, but I'm afraid that's not what I was asking.

    About events we do see now, it's obvious that as time passes and we look again, we will see them "growing old".

    My question was about the boundary of the visible universe. Will it get bigger? I think it will, but even if bigger in volume, will it encompass a larger number of material bodies than it does now? (will in the future new galaxies appear in the sky? I don't mean "new" in terms of formation stage, I mean galaxies which we don't see AT ALL now, not even in their formation stage, because they are beyond our visible universe)

    Anticipating to answers, I tell you the guessing which was the reason for my question:
    If I imagine the universe some billion years into the future (assuming the earth will still exist), it will have expanded and cooled down much more, it will be much less dense that now. I guess that distant cosmic objects will have got so far apart from eachother that the heavens will look mostly black and empty to our descendants.
    If so, that would mean that objects we now see will gradually disappear from our skies.
    Yet on the other hand, it seems that the longer we wait, we allow light from very distant objects to have had more time to reach us, so those new (not visible today) objects could finally appear in our skies.
    I wonder which of the 2 is the correct view: in the future will there be more visible objects in the sky or less? (or just the same -but obviously more matured-)
    Last edited by a moderator: Aug 27, 2004
  5. Aug 27, 2004 #4
    yes, new objects will appear, as well others will not be ever visible. this is due to the expansion of spacetime

    This will also happen. Our future is very dark :yuck:
  6. Aug 27, 2004 #5
    TX! So both will happen, some objects will disappear from our sight and other new ones will show up.
    What will the net effect be? will the skies look darker and darker ? (more objects will disappear than new ones appearing?)

    Is it correct to say that even if objects actually remain within our visible universe boundary, they will get so far away that their light will be much fainter? (so the sky will get even darker due to this additional effect)

    Has any such effect ever been seen? a new object suddenly appearing in the telescopes (and I don't mean due to increased resolution, I mean really due to the object crossing the boundary from non-visible to visible universe), or the opposite, some object having suddenly disappeared from sight?
    Last edited by a moderator: Aug 27, 2004
  7. Aug 27, 2004 #6
    in the long future, that's correct
  8. Aug 27, 2004 #7


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    New objects like stars or aged galaxies will not suddenly appear at the edge of the visible universe. Due to the finite speed of light, as we look further away, we are seeing into the past. The view at the "edge" of the visible universe (13.7 billion light years away) is the Big Bang itself.

    Like LURCH said, we can see the events that have unfolded within our visible universe since the Big Bang. The more distant the object, the further into its past we are seeing.

    As time goes on and the radius of our visible universe grows, there will be more of the early formational period coming into view. Perhaps we'll be able to find more proto-galaxies (and there will be more developing galaxies within our field of view).

    But telescopic views of that timeframe are very limited because they're so incredibly faint (and prior to 300,000 years after the Big Bang, the universe was opaque to visible light). So, we're far from the capability of being able to see objects suddenly crossing into view.
  9. Aug 27, 2004 #8
    TX Phobos !

    It seems we have a dark future ... :-/

    By the way, it would be so nice if we lived in a denser (or earlier) region of space, being able to see in the night skies with the naked eye clear galaxies, quasars and blazars emiting huge jets of particles, bright clouds of cosmic dust, and every other types of beautiful cosmic objects / events (maybe even seeing with the naked eye the action of some black hole on it's surroundings?)

    Wouldn't it be great? (and astronomy much easier!) The fact the our future looks like there's no chance, but we will see less and less fun in our skies, makes me sad and feel like we have evolved too late or in a wrong region of the universe :-(

    Just positive is that by our engineering we could develop telescopes to compensate a bit for this bad luck ....
    Last edited by a moderator: Aug 27, 2004
  10. Aug 27, 2004 #9


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    I would like to ask a slightly different question.

    After the big bang the universe started expanding, and some stars are moving away from us and some are moving at us.

    I was wondering what is the initial point (if known) or otherwise, the origin, of the big bang. I'm not familiar with how much of the known universe we've covered, but I've seen a rough map of the universe in journal Discover (www.discover.com) of jan 2004, vol 25, number1. I believe the map was made from NASA's WMAP.

    So is it safe to assume that the big bang occured in the middle of the known universe (0,0,0) or at some other point?
  11. Aug 27, 2004 #10


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    To repeat what I said in another thread:
    "Grizzlycomet: "Where did the Big Bang start from? Here!" (points to own heart)
    The Binary Monster: "Actually, it started here!" (points to own heart)
    ;oih?£^fÅioh {denizen of a minor planet, orbiting a minor star, in a minor galaxy, in a nameless small galaxy cluster, ~3,234 Mpc from the Milky Way}: "The Big Bang started here!!!!!!!!" (points tactile sensor #345 to neutrino-sensory lobe #5)

    How can this be? :confused: "
  12. Aug 27, 2004 #11


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    well its only fair to assume like with any explosion there would be residual mass of the explosive. if there remains such evidence at the origin (in a form of maybe space-time vortex) - wont it be intelligent to point our spectrometers and other telescopes at the source?

    or is there a source?

    Edit: i thought of something.. if all objects (stars, planets, etc) are moving at this point in time, then no one object can be the center of the universe
    Last edited: Aug 27, 2004
  13. Aug 27, 2004 #12
    As pointed by Nereid, there's no point or region which can be considered as "a source" or "center" of the universe.

    The famous analogy of a balloon with dots painted on it and being inflated is still useful: all dots were once together, later all dots are apart from eachother. Yet no dot has the privilege of having stayed at the origin, or if you like it better, any dot could say he was the origin.

    Just pay attention not to picture the universe literally as an expanding spherical surface. The balloon surface expands within our 3-dimesional space and leaves an increasing hollow sphere inside itself. The spacetime forming our universe indeed grows (is inflated), but it does not grow within any external space, it is itself the only space there is. And therefore of course it doesn't have any "hollow" in the center either!

    Even you may not picture the sphere surface growing within any external space, you may picture it growing with time. In fact this is the conventional visualization, a spherical surface being inflated, and the radial dimension from the center of the sphere pointing outwards represents the passing of time.
    Again warning, the surface does not grow within time. Out of the surface there is no time at all, the only time extension existing is created together with the space expansion (at any moment of the expansion, the only time existing (elapsed) is the one inside the sphere)

    And if you got that right you will now understand that whatever direction we look in the skies happens to be the center (literally!). You've probably heard about the cosmic background radiation of the COBE, it's what you describe as "the residual of the explosion", and it comes from everywhere all around.
    In fact, looking "anywhere all around" we are looking at a single point, the origin, but as we just said the origin is our own location too, so .....

    As the easterns guessed long ago,the extreme opposites connect with eachother, zero and infinite, up and down, big and small, far and near, good and bad ...... are together hand in hand
  14. Aug 27, 2004 #13


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    You are absolutely right. In the infinite expanding universe of SBB theory (and in some other models), every observer is entitled to his own reference frame, so no one observer can claim to be the center of the universe. Every observer will see his own reference frame as unique, and will wonder about the characteristics conspire to make his location SEEM to be the center of the universe, (like light from more distant domains being redshifted relative to his own neighborhood).

    Right now, an expansionary model of cosmology (and especially an accelerating expansionary variant) holds sway, but science is a game of leapfrog, and I look for advances in telescope resolution and instrument sensitivity in the next few years to drive a swing toward observational astronomy that will encourage innovation in the more purely theoretically-derived branches of cosmology.
  15. Aug 28, 2004 #14


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    Think about it. I really think you are not seeing the big picture. Modern cosmology is very hard to conceptulize. Give it an equal chance. There are so many contradictions to what you think you see that you must give it up eventually. You are not the first to ask the questions you have asked.
    Last edited: Aug 28, 2004
  16. Aug 28, 2004 #15
    For the first few hundred thousand years the universe was opaque. When the temperature dropped below about 3000K it became transparent. All around us we see the (radiation from) the opaque matter just before it became transparent. We see it redshifted and its called the microwave background. If we wait then the opaque matter we are seeing now will have become transparent and we will see the opaque matter further away, so in a sense we will see new objects, but since it will look much the same as the old we probably won't notice it (although I imagine we could tell something by seeing how the microwave background fluctuations change with time). However, new galaxies and the like won't suddenly come into view.
  17. Aug 28, 2004 #16
    Hi Chronos, as you did not quote anything, may I ask you about which user / statement you are refering ?
  18. Aug 30, 2004 #17


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    To help clarify...

    According to Big Bang theory, there is no center (or edge) to the universe in 3D space. Except in local regions where gravity dominates (like in a galaxy of stars), the expansion of space occurs in every direction at every point. Essentially, the Big Bang happened everywhere in the universe. The Big Bang was not an explosion of stuff from a point into empty space. It was the beginning and rapid expansion of all space itself.

    The reason that "some stars are moving at us" is because of gravity in local regions, and not because of a differential movement away from some big bang center.
  19. Aug 30, 2004 #18


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    Apologies, I was hasty, hence vague. There is a hard limit to the distance we will ever be able to see - which is about 13.4 billion light years. Beyond that the universe is opaque, as other posters have noted.
  20. Sep 8, 2004 #19
    Thank you all.
    Just for my confirmation:
    You all seem to focus on confirming that we won't see further into the past (as even if we could, we would find the opaque times), and that we will just see the same regions of space we can see now evolving through time (e.g. where we now see a cloud of dust we might eventually see it condensing into a protogalaxy).

    My wondering was not so much about seeing "further into the past", but "a wider area sideways". I mean, not events which are beyond our visible horizon "more into the past", but just beyond in "side-distance".
    Not sure if I explain myself, I mean in a typical spacetime diagram, events which lie outside of our past light cone because they are "too much to the right or to the left", will become visible sometime ahead in our future.

    I understand from your explanation that such events can only be the evolution in time of events we can already see now, and not light (or any radiation) coming from any truly "newly observed" matter (which we can not see already in some form).
    Not even if some bunch of matter currently beyond our horizon, was travelling fast towards us, light emitted by it could never reach us?
    Tx again!
  21. Sep 9, 2004 #20


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    In my opinion, everything that will ever be observable already is observable. Distant galaxies will not 'blink' out of existence, nor will 'new' galaxies pop into view. Explaining it is a little more complicated. Best way I can think of is to say we are already within the light cone of the observable universe. I can't imagine it otherwise without resulting in observations of remote objects that are reverse aging.
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