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
To answer that.
Yes.
If B maintains its position relative to A.
Passing the Hubble volume “Barrier” is irrelevant. Well.. it is, but B is only outside and A is inside because of where you consider the Hubble Barrier to be between them. (From a viewing position)
If A can see B and B can see A and the Hubble Volume Barrier is from our position (Earth) We’d see A but not B since this Barrier is between them. If we are at position A, we’d see B as the Barrier will have extended out past B as much as it would have view from Earths location.
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