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Nothing faster than the speed of light; except the expanding universe?

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  • 14-02-2012 12:15pm
    #1
    Amtmann
    Closed Accounts Posts: 6,093 ✭✭✭


    From our vantage point, the universe's horizon lies at a distance of around 14bn light years, because that's the age of the universe, so we can't see beyond that, because the universe didn't yet exist.

    Many astrophysicists (Tyson, Greene, et al.) think that the universe extends far beyond the horizon that we can see.

    Does this mean that the universe expanded faster than the speed of light during its inflationary phase?


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    #2
    Spear
    Moderators, Computer Games Moderators, Technology & Internet Moderators, Help & Feedback Category Moderators Posts: 25,130 CMod ✭✭✭✭Spear


    Amtmann wrote: »

    Does this mean that the universe expanded faster than the speed of light during its inflationary phase?

    It's called the Horizon Problem in cosmology:

    http://en.wikipedia.org/wiki/The_horizon_problem


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    #3
    AugustusMinimus
    Registered Users Posts: 4,547 ✭✭✭AugustusMinimus


    Amtmann wrote: »
    From our vantage point, the universe's horizon lies at a distance of around 14bn light years, because that's the age of the universe, so we can't see beyond that, because the universe didn't yet exist.

    Many astrophysicists (Tyson, Greene, et al.) think that the universe extends far beyond the horizon that we can see.

    Does this mean that the universe expanded faster than the speed of light during its inflationary phase?

    1. I don't think that the cosmic horizon is solely linked to the age of the universe. The rate at which the universe is expanding and the radius of the total universe also play a part. From what I've read, the cosmic horizon is actually around 16 Billion light years from earth.

    2. Indeed. Scientists really do not know the entire scale of the unobservable universe. Given that both light and gravity travel at the speed of light, we will prob never know because even the gravitational effects of objects on the other side of the horizon is lost on us.


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    #4
    Rubecula
    Registered Users Posts: 8,551 ✭✭✭Rubecula


    The speed of light is a constant throughout our universe as far as we know. The universe itself is not restricted by this.

    I don't think there is actually a limit to the speed of space's expansion. Or at least not one that we know of.

    This is why there are theories of travelling fster than light by warping space around the vessel. Not moving the ship at FTL speeds but moving the space itself.


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    #5
    Anonymo
    Registered Users Posts: 151 ✭✭Anonymo


    Rubecula wrote: »
    The speed of light is a constant throughout our universe as far as we know. The universe itself is not restricted by this.

    I don't think there is actually a limit to the speed of space's expansion. Or at least not one that we know of.

    This is why there are theories of travelling fster than light by warping space around the vessel. Not moving the ship at FTL speeds but moving the space itself.

    Yep the main point is that there is no information being passed (you can take as a definition of this that no photons are being transmitted) at faster than light if space expands at superluminal speeds. What special relativity constrains is the acceleration of an object at rest to speeds faster than light. There is no acceleration of objects via the expansion of spacetime. Rather it is the space between the objects that grows. This is a fundamental difference to changing the inertia of the object itself, and is the reason there is no contradiction.


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