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From Wikipedia:

Some parts of the Universe are too far away for the light emitted since the Big Bang to have had enough time to reach Earth, so these portions of the Universe lie outside the observable universe. In the future, light from distant galaxies will have had more time to travel, so additional regions will become observable

Is this really possible? I also read another question but is not exactly what I wanted to ask.

To explain the question let us consider the universe at two different points of time (A) at age of X/2 years and the current universe (B), at age of X years.

Now at A, anything beyond X/2 light years away from earth is moving faster than speed of light and light from it transmitted at that point will never reach earth. If we consider a bigger sphere of X light years, light started from these objects, in past X/2 years are already present in the X/2 light year sphere (expanding slower than speed of light) and will reach earth in the next X/2 years or by the time universe is X years old.

Now at B, the current age of X, an object 2X light years away from earth is already something that was inside the X light year spear at time point A (considering expansion rate increases). So the light from such an object has already reached us (light from that object was less than X/2 light years away X/2 years back).

So considering X as 13.7 billion light years, question is can we safely say that light from objects within 27.4 billion light years distance from earth has already reached us and anything beyond that is permanently invisible for an expanding and accelerating universe any time in future?

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marked as duplicate by Kyle Kanos, Floris, Brandon Enright, Pranav Hosangadi, John Rennie Feb 28 '15 at 6:36

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