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Is there more than just one Universe?

  1. Dec 29, 2003 #1
    Hi i am new member looking to learn from you guys
    Can any one answer these questions if so ui would be most grateful.

    Is there more than just one Universe.

    Is it known where our Universe starts and ends.

    Do we need to know the outside edges of our Universe before we can find the centre of it.

    Is the sun really the centre of our Universe.

    If it definately is the centre is the centre of our Universe - how do we know it is.

    Thanks in advance, Fagin.
  2. jcsd
  3. Dec 29, 2003 #2
    Hey Fagin!

    I'm just as new as you, but I thought I'd see if I could help in any way...

    Is there more than just one Universe.

    I suggest that you read the cover feature of Scientific American May 2003, it covers the different theories which suggest multiple universes in plain english... In summary of the article:

    The farthest away that we can see is the distance that light has travelled since the big bang, if there is more space beyond that distance, it can be considered another universe because we can never reach it or see it. This is what the author, Max Tegmark labels as 'Level 1 Multiverse'.

    Chaotic eternal inflation, a highjacked version of Guth's inflationary big bang model suggests that there ae an infinite set of level 1 multiverses, each of which could conceivably have different properties and laws, The 'Level 2 Multiverse' is the collection of all universes.

    The 'Level 3 Multiverse' arises from the many worlds interpretation of quantum mechanics. Consider the standard 2 slit experiment, where light (photons) are directed towards a surface with 2 holes in it. Each photon has a choice of heading through either of the holes. The manyworlds interpretation suggests that the universe splits into 2 seperate universes when such a decision must be made, each possibility exists in a 'parallel' universe.

    The Level 1 and 2 Multiverses are currently hardly science in my honest opinion because there is no possibility to observe them, or their effects on our universe, and not much chance of observing them at any point in the future.
    The problem with the concept of the many worlds interpretation(multiverse 3) is that it is not the most efficient way for quantum mechanics to work. It requires the existance of an infinite number of universes, an seriously redundant concept in light of other suggested interpretations. In physics, like all science, we try to find the most concise and efficient solution to a given problem, infinite unobservable universes are neither concise nor efficient, not to mention conceptual problems which arise (ie. why do we exist in this particular universe?).

    So thats question 1 taken care of....... (is there more than one universe? some scientists say yes, but at this point none of our best theories seem to require them(although they make for great articles in popsci magazines)

    Is it known where our Universe starts and ends.

    Not sure whether you are refering to the space or time coordinates....
    Our best theory of where the universe starts is still the big bang theory, which came about from the observed redshift of astronomical objects(redshift of light = they are moving away from us). So, ignoring an cyclic (ekpyrotic) models, we can be pretty confident that the universe began with a big bang singularity around (off the top of my head might be wrong) 15 billion years ago (i think...). Its not right to think about some spot in space where the universe began b/c as the universe expanded, it was the space itself which was expanding, therefore every point in space is just as much the start as any other.
    Where does the universe end? Lets start with when. Depeding on the value of a number called the cosmological constant, the universe may continue to expand forever, slow down an eventually stop, or it may begin to recollapse at some point in the future (big crunch). The cosmoconstant depends on the average density of space in the universe. Where does the universe end? If you are talking about like an edge here it is a bit difficult to picture. As far as I know it is wrong to think about the universe as being something like the inside of a ball, if you hollow out a tenise ball you have 3 dimensional space within it and a border (that is the intuitive concept of the universe), that same tenise ball, when looked at from the outside has a 2 dimensional surface (an ant standing on a tenise ball will see infront behind and left right) just as we see the surface of the earth as 2 dimensional (longitude latitude right?). So we know that the surface of the tenise ball isnt our universe as we observe 3 spacial dimensions, the universe then, can be thought of as the 3 dimensional surface of some 4 dimensional object. Which makes it really tough to think about edges, depending on curvature it could be a 4sphere (if you fly through space in 1 direction for long enough you will end up where you started type thing), so we don't really know at this point.

    Do we need to know the outside edges of our Universe before we can find the centre of it

    Why do we need to find the center?

    Is the sun really the centre of our Universe.

    If it definately is the centre is the centre of our Universe - how do we know it is.

    If the universe is infinite then every point can rightly be considered the center, however this is very unlikely, the sun itself being the center of the universe is even more unlikely though(I mean c'mon its not near the center of a galaxy!)

    Hope I could help, remember the power of google in your search for knowledge!

  4. Dec 30, 2003 #3
    Thanks very much Ultan, that answers questions just nicely, i am most grateful.

    Thanks again, Fagin
  5. Dec 30, 2003 #4
    Glad I could help!

  6. Jan 3, 2004 #5
    More food for thought; Did you know that the universe is now said to be "infinite and flat" due to recently accumulated data measuring the universe's CMB - or Cosmic Microwave Background (said to be the microwave "echo" of the Big Bang), the universe is said to be 13.7 billion years old, and is said to be comprised of %4 matter, %23 dark matter and %73 dark energy? Oh, and researchers now contend that the "Speed of Gravity" is roughly %95 of the "Speed of Light"? I found these facts to be quite interesting, I thought I'd share them.
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