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Thread: The Center of the Observable Universe?

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  1. #1

    Default The Center of the Observable Universe?

    First off, let's start by saying that when I use the word "universe" from here on out I mean the observable universe. So here we go, I'm confused by this...

    The universe is expanding infinitely in every direction and the distance from the observer -- us -- to the edges of the Universe in every direction is always more or less equidistant, meaning it must be a roughly spherical shape, right?

    And, logically, because the Universe is spherical and we are more or less equidistant to its edges, we have to be in the exact center -- because we are observing it around us?

    Which means that, if Zaphod Beeblebrox on Omnia Persei Delta 9 a billion light years away (but still within our observable Universe!) happens to be observing the Universe at the exact same time I am, both of our planets are by definition simultaneously in the exact center of the Universe despite being 9.461 × 10^21 km apart from eachother?

    Wouldn't the edges of Zaphod's observable Universe and the edges of my observable Universe have to be about the same because the Universe has a finite age, no matter where in the observable Universe Zaphod is observing it from?

    Surely I'm missing something

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  2. #2

    Default Re: The Center of the Observable Universe?

    The thing to consider is that our observable universe is almost certainly not the entire universe. There are some models of Inflation where our observable universe is like a grain of sand on the Earth when compared to the actual size of the universe. The universe may in fact be infinite in size as far as we know.

    The observable universe would look much different billion miles from Earth, because some light from places that haven't reached Earth yet will have reached this new location, and some light that has reached Earth will not have reached there either.

    Lawrence Krauss puts it this way: Either nowhere is the center of the universe, or everywhere is the center of the universe, depending on your mood.

    Edit: Here's a picture I half-assed in paint to help illustrate: (not to scale )
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    Last edited by Gordon Freynman; August 31, 2010 at 05:26 PM.



  3. #3

    Default Re: The Center of the Observable Universe?

    Quote Originally Posted by Justinian View Post
    And, logically, because the Universe is spherical and we are more or less equidistant to its edges, we have to be in the exact center -- because we are observing it around us?
    If we're merely more or less equidistant to its edges we can't possibly be in the exact center. We could more or less be in the center though.
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  4. #4

    Default Re: The Center of the Observable Universe?

    Quote Originally Posted by Gaidin View Post
    If we're merely more or less equidistant to its edges we can't possibly be in the exact center. We could more or less be in the center though.
    Well, let me correct myself, in our frame of reference (ie whenever a human is doing the observing) we are exactly equidistant from the edges of the Universe. At least that's my understanding of it.

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  5. #5
    mp0295's Avatar Vicarius
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    Default Re: The Center of the Observable Universe?

    They would be at the center of their own observable universe. Like others have said, we're only seeing what we think is a tiny part of the universe. As far as i have learned, the universe isn't expanding into something, but rather space itself is expanding. It's hard to grasp but i like the metaphor of the universe being on the surface of a balloon that is inflating. Two dots on the ballon would being going further away. I don't know how accurate that metaphor is but i like it.

    It gets more complicated because we have three dimension of space (that we can see anyways) and the surface of a balloon is 2D, but whatever. And i should also say im posting with the bias of the theory that makes more sense to me.
    Last edited by mp0295; September 01, 2010 at 10:31 AM.


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  6. #6

    Default Re: The Center of the Observable Universe?

    As others have stated above, everyone is exactly in the center of their own observable universe because what you can observe is limited by the speed of light. I.e. because space is expanding and thus all galaxies are moving away from each other that means the farther away a galaxy is, the faster away it is moving (or else it wouldn't be moving away from the galaxies between us and them) there comes a distance away from the observer where things are moving away faster than the speed of light and thus you will never be able observe them.

    The discovery that the expansion of the universe is accelerating has another interesting implication. This means that at some point in the future even our nearest galaxy will be moving away faster than the speed of light and we will not be able to observe it. This means at some point the observable universe will only be the milky way, and that science would have to conclude there is nothing else in the universe.

    The idea of the observable universe is relatively simple to get your mine around. What is difficult to get ones mind around is that there is no "edge" of the universe. Intuitively its easy to think of the big bang as a conventional explosion that send things flying away from eachother and thus there should be some galaxy on the edge of this explosion where if you look in one direction you would see the center of the universe and if you look in the opposite direction you would see nothing but blackness. This would be true if space were a ridged grid like Newton thought, but we know now that space is curved by matter. The matter in the universe curves space back in on itself such that you could travel in a "straight" line away from earth and never reach the "edge" of the universe because the curvature of space will always steer you back into the universe. This also applies to light such that if you were on the "edge" of the universe if you looked back towards the "center" of the universe you would see bunch of galaxies, but when if you then turned 180 degrees you would also see a bunch of galaxies, which would look practically identical to your view of the "center". Thus there is no center, nor an edge to the universe.

    Prof. Lawrence Krauss does a much better job at explaning this than I, look him up on Youtube.

  7. #7

    Default Re: The Center of the Observable Universe?

    Quote Originally Posted by Sphere View Post
    As others have stated above, everyone is exactly in the center of their own observable universe because what you can observe is limited by the speed of light. I.e. because space is expanding and thus all galaxies are moving away from each other that means the farther away a galaxy is, the faster away it is moving (or else it wouldn't be moving away from the galaxies between us and them) there comes a distance away from the observer where things are moving away faster than the speed of light and thus you will never be able observe them.
    Thanks for the explanation! The only thing I don't get is this last line here -- I thought nothing could move faster than the speed of light?

    Patron of Felixion, Ulyaoth, Reidy, Ran Taro and Darth Red
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  8. #8

    Default Re: The Center of the Observable Universe?

    Quote Originally Posted by Justinian View Post
    I thought nothing could move faster than the speed of light?
    Nothing can move faster than the speed of light relative to the space around it (unless you believe in tachyons ). Space itself however is not bound by this condition and can expand and whatever rate it wants given the proper conditions.



  9. #9
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    Default Re: The Center of the Observable Universe?

    Quote Originally Posted by Justinian View Post
    Thanks for the explanation! The only thing I don't get is this last line here -- I thought nothing could move faster than the speed of light?
    Speed is distance over time. If you change the distance you can surpass the normal speed of light (well you can't but relative to the present or unaltered universe you can) in a vacuum by cutting the distance (warp drive). In this case because of the distance and the natural expansion of space between objects (growing at an exponential rate by distance) the distance between galaxies is growing faster than the speed of light. Some galaxies like the andromeda are heading to us faster than this expansion rate but for the most part the farther something is the faster it's receding from us. This is how we predicted the big bang before observational data confirmed it's existence. Hubble discovered this law.

    The visible universe is only a small fraction of the entire universe, the universe expanded initially at many times the speed of light in all directions and is continuously expanding at an ever increasing rate. The visible universe is all we can see because any further away and light hasn't had a chance to reach earth yet meaning we can't use a telescope to see past it. There's not actually a border between the visible universe and the 'invisible' universe thus if you move your planet to Betelgeuse the new visible universe is different because Betelgeuse has a different location and thus the light has had the chance to reach it.
    Last edited by Elfdude; September 05, 2010 at 05:28 PM.

  10. #10
    mp0295's Avatar Vicarius
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    Default Re: The Center of the Observable Universe?

    yeah pretty much what he said. It also depends on the exact curvature of the universe about the 'edges'


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    Default Re: The Center of the Observable Universe?

    Unless you are standing in a place where you can see the "edge" the universe, then you are always the centre of the observable universe...
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    Both male and female walruses have tusks and have been observed using these overgrown teeth to help pull themselves out of the water.

    The mustached and long-tusked walrus is most often found near the Arctic Circle, lying on the ice with hundreds of companions. These marine mammals are extremely sociable, prone to loudly bellowing and snorting at one another, but are aggressive during mating season. With wrinkled brown and pink hides, walruses are distinguished by their long white tusks, grizzly whiskers, flat flipper, and bodies full of blubber.
    Walruses use their iconic long tusks for a variety of reasons, each of which makes their lives in the Arctic a bit easier. They use them to haul their enormous bodies out of frigid waters, thus their "tooth-walking" label, and to break breathing holes into ice from below. Their tusks, which are found on both males and females, can extend to about three feet (one meter), and are, in fact, large canine teeth, which grow throughout their lives. Male walruses, or bulls, also employ their tusks aggressively to maintain territory and, during mating season, to protect their harems of females, or cows.
    The walrus' other characteristic features are equally useful. As their favorite meals, particularly shellfish, are found near the dark ocean floor, walruses use their extremely sensitive whiskers, called mustacial vibrissae, as detection devices. Their blubbery bodies allow them to live comfortably in the Arctic region—walruses are capable of slowing their heartbeats in order to withstand the polar temperatures of the surrounding waters.
    The two subspecies of walrus are divided geographically. Atlantic walruses inhabit coastal areas from northeastern Canada to Greenland, while Pacific walruses inhabit the northern seas off Russia and Alaska, migrating seasonally from their southern range in the Bering Sea—where they are found on the pack ice in winter—to the Chukchi Sea. Female Pacific walruses give birth to calves during the spring migration north.
    Only Native Americans are currently allowed to hunt walruses, as the species' survival was threatened by past overhunting. Their tusks, oil, skin, and meat were so sought after in the 18th and 19th centuries that the walrus was hunted to extinction in the Gulf of St. Lawrence and around Sable Island, off the coast of Nova Scotia.

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    Default Re: The Center of the Observable Universe?

    "I'm an eye, a mechanical eye. I the machine show your world in a way only I can see it. I free myself for today and forever from human immobility. I'm in constant movement, I approach and pull away from objects, I creep under them, I run along side a running horses mouth. I fall and rise with the falling and rising bodies.

    This is I, the machine. Manouvering in the chaotic movements, recording one movement after another in the most complex combinations. Freed from the boundaries of time and space I coordinate any and all points of the universe wherever I want them to be. My way leads to the creation of a fresh perception of the world.

    Thus I explain in a new way the world unknown to you." - From a manifesto written in 1923 by Dziga Vertov, the Russian film director.
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