I’m trying to wrap my head around an apparent paradox. I could not find this by searching and I apologize if this breaks the rules for hypotheticals.
The Hubble volume is a region in space containing everything we can physically interact with. Objects outside of our Hubble volume are receding away from us faster than the speed of light and are therefore impossible to interact with for us.
Now consider an object A at the very edge of our Hubble Volume. It is receding away from us near the speed of light. Near object A is object B. Object B is at a greater distance from us than A, such that B lies outside of our Hubble volume. According to my understanding of the Hubble volume, we can never interact with Object B under any circumstances.
However, imagine the following complication of this setup: Object B is a spaceship, and it maintains an equal distance to Object A at all times by firing its thrusters very rarely to make up for the distance increased between it and Object A due to the expansion of space.
Now, Object A is inside our Hubble volume. Object B is outside of it, but at a constant distance from Object A.
We now travel to Object A. By the time we reach Object A, where is Object B? Can we reach it? Similarly, could the captain of Object B launch a dropship in advance to Object A to meet us when we arrive?
In: Physics
If Object B is able to use enough (theoretical thrust) to maintain a constant distance from Object A, then it will remain at that constant distance from A and be reachable since its negating the whole problem of the universe expanding at an accelerating rate. Also, the Hubble volume is relative to your position within the universe. If someone is at Object B, then Object A would be within their Hubble Volume and remain reachable, so they could meet us.
The concept of the Hubble Volume is that from our current position, things at the edge of that “bubble” are accelerating faster than the speed of light that even if we could travel at 99.9999~ and so on the % of the speed of light from this very moment, we wouldn’t be able to reach it. However, if we were a light year over when we started at this very moment, we could reach it.
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