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Other Universes?

  1. Mar 21, 2003 #1
    I seem to remember that the main argument against there being other universes is that the sky would be filled with light. But since light scatters with distance wouldn't the lack of light from other universes might also be an indication of immense distances?

    To piggy-back off another of my questions...concerning the "universe is expanding at greater rates or light is slowing down" question, why would light not slow down or at least change direction over distances from a gravitational field? The answer that was provided me in the other thread said in a roundabout way that light is accelerating away at a great enough rate that it will never succomb to gravitational fields. But that doesn't sufficiently answer my question. First, what provides for constant acceleration? Wouldn't light gain all of its acceleration and properties from the properties of the material and motion that it was derived from (the electron)? And consequently, wouldn't all acceleration be derived from the moment it left the electron?

    Secondly, one of my earlier questions was that since light is affected by strong gravitational fields, wouldn't it show that light has mass? However, it has been told to me that gravity is an electromagnetic field and since light is also an electromagnetic field it is affected by that "part" of gravity and not the acceleration or "pull" towards the mass itself. I'm not entirely convinced, could somebody explain this to me? Why would the attraction between objects "with mass" absolutely not also be due to electromagnetic forces?

    Basically, how can it be proven that light doesn't have mass? Additionally, how can it be proven that light has constant acceleration? Also, since one of my questions before was that since gravity affects light's direction and acceleration within very strong gravitational fields, why wouldn't it also affect light, albeit to a less extent over large distances, especially since gravity shares at least one quality with light itself?

    Then there is the whole gravitational force against mass anyway. Why isn't there a constant decceleration away from (or acceleration towards the object of greater mass) that will simply change the shape and distance of an orbit depending on mass and velocity? Ok, let's say that I'm in a spaceship orbitting earth. My orbitting speed around the earth is very great, but my relative distance to the earth doesn't change except for small waves or undulations toward and away from the earth during the orbit. Oh, and I'm spinning at a very high rate as well. And of course the earth is spinning. A small explosion in one of my compartments sends a piece of metal out and away from the spacecraft. Will it have some recursive direction from my orbit and spin? If it does then it would be impossible for it to accelerate at a right angle from the surface of my spacecraft. Not to mention that since my position relative to the object changes and doesn't maintain 90 degrees. And since my rotation around the earth didn't stop I would be getting periodically closer and farther away in intervals along its path away from me. This would create a greater and smaller "gravitational" pull on the object while the overall net effect would be dissipating acceleration toward me, but also dissipating acceleration away from me--that combined with the recursive direction and spin of the object, as well as the lack of any 90 degree relative position would necessarily send the object in an orbital path--the object itself does not slow to a stop, but instead it changes direction. Why doesn't this then happen with the photon in relation to the electron? Basically what I'm asking is, if the entire universe were summed up with me and a baseball, and I were to throw the ball as hard as I can, wouldn't the ball eventually either slow if it is at constant right angle to me and no outside forces were involved, or maintain some or all speed and change direction (nevermind that it would be impossible if I am revolving and orbiting around something myself)? If I were to replace the spaceship with an electron and the space junk with a photon, why wouldn't the photon eventually change direction even if it doesn't change speed (thus the relative distance from the spaceship/electron would conversely widen and become more narrow or simply maintain distance over time)? Thus light could maintain speed while changing direction (velocity) and the red shift would be at least partially explained without going out on a limb and stating that the universe is expanding at greater and greater rates?

    And here's the big question...How can the universe have a finite beginning and an infinite lifespan? Nevermind God going, "poof" there it is... I'm serious about this. Either the universe is a closed system that expands and converges or it is open with other "universes" out there. It cannot have begun at a single point and time and expand forever--it doesn't make sense. How did the matter get there to begin with?

    I hope that gets some people thinking rather than quoting from science books and relying on other people's past conjectures. BTW, I might be ignorant, but I'm not stupid...so give it to me straight. :)
  2. jcsd
  3. Mar 21, 2003 #2


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    This has nothing to do with other universes, This has been used as an argument that there cannot be infinitly many stars, but even that does not hold water. The existance of other universes is pure theory, we have no way of detecting their existance or none existance. Light from another universe cannot reach ours. If it did then it would not be a different universe.
    Light travels at a constant velocity, it is not accelerating. Light follows geodesics of the universe, these bend in the neighborhood of massive objects, therefore light appears to be effected by gravity. It is all a matter of persepective, since geodesics DEFINE a stright line in the universe, light IS going in a straight line. The fact is the universe is a bit more complicated then we care to admit. It is our definition of straight that is incorrect, not the path of the light.
    OK, since the acceleration of light is zero, it is constant, however It is the constant VELOCITY of light which is of interest. The speed of light is given by c = 1/Sqrt( e0 m0)) were e0(episilon sub zero) represents the premitivity of free space and m0 (mu sub zero) is the permiability of free space. This relationship was derived by Maxwell in 1867 and is the source of Einsteins postulate of a constant speed of light.

    I am not sure what this means. Any object ejected from your ship will have some trajectory, once it leaves your vessel the only force of any significane acting on it will be the force of the earths gravity. The object will fall into an orbit that will be determined by its velocity.

    You are NOT free to choose orbital distance AND velocity, your orbital velocity determines the distance you orbit from the center of the earth.

    Your concept of the interaction of photon and electron is bad, an electron is NOT a ball, and a photon is NOT like space junk, the analogy simply does not work.

    If you were to throw a ball with NO other forces acting on it, it would NOT slow down, it would continue with constant velocity.

    You would be well served to find a good physics text and start learning, there is much that you do not understand.

    Good luck.
    Last edited: Mar 21, 2003
  4. Mar 21, 2003 #3
    how can you make that big posts?
    do you know that i pay for my internet access?
    when will i read them?

    regarding the subject only i have this comment:
    universe for mua is set/unity of all the matter.
    how can there b another universe then?
    how should i imagine 'another universe'?
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