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Message: <blockquote data-quote="briggart" data-source="post: 9817101" data-attributes="member: 6805135">This is correct, but it is mostly just a coincidence. There are few things that are mixed together here, which are clearly related but I do not think they apply to the point you are trying to make.When we speak of observable universe, we usually refer to the farthest distance from which a signal could have reached us by now, which gives that 45 something billion years. The Hubble radius is the distance in which "current" galaxy recession velocity would be equal to c according to Hubble law. It is in general not the same as the radius of the observable universe, but it is typically close to it.Finally,  we have the distance a photon can travel from now to the end of time.If our universe were made up by regular stuff (i.e. stuff with "not too big" negative pressure), the radius of the observable universe and the Hubble radius both grow with time faster than than the expansion rate, while the future horizon is infinite. Given enough time, and light from anywhere in the universe will reach us, even if the emitter is currently superluminal with respect to us.However, we seem to live in a spatially flat universe which has entered a phase of dark energy dominated expansion which, were it to continue indefinitely, would lead to a finite future horizon. As it is now, nothing that is currently emitted farther than a few billion light years will ever reach us, but this is a consequence of the fact that dark energy leads to an accelerated expansion, not to the fact that some stuff is moving in some sense faster than light. He told us that in regard to inertial frames in special relativity, not general relativity which is the relevant framework here. Locally, GR reduces to SR, but on cosmological scales there is no global inertial frame in which to apply SR results.I think you are looking at this from a SR point of view where spacetime has an existence of its own. In GR spacetime is nothing more than the 4D-geometric properties of the distribution of stuff, it would not expand if stuff were not moving away from each other.  At the very least, GR gives us a loop: stuff is moving away because space is expanding, but space is expanding because stuff is moving away.  Regarding acceleration, if you take the position that dark energy is a pure cosmological constant, then the force you are looking for is gravity. Otherwise you need some dynamical component with large negative pressure, which you can interprete as a force if you like, but in the end it is just the request of high symmetry and the initial conditions of the problem which lead to an accelerated expansion.</blockquote>

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