I’m not saying these answers are all right, but offering multiple perspectives!

- If the infinity is complete, it could be a finite object at the same time! For example, if you took a small section of a sphere and expanded it out in all directions, following it’s curve it would have a complete sphere! It could also work for a string connected at both ends, like a rubber band! I like the rubber band, because though the loop is infinite, it’s extremely versatile still!
- If the infinity is incomplete, unforeseeable, or assumed to never have an end, like a rolling river, the spinning of an asteroid in space, or the expansion of space itself, then 1/4 would be a great reference point. If you knew where 1/4 was, you would have to know the current size of it. That’s fantastic! If space is expanding in all directions, you could still triangulate your position and travel, just take into account the rate of expansion. Kind of like how you have to take into account the acceleration of gravity when landing a plane, rocket or catching a baseball.
- If the infinity is not part of a physical object at all, but instead an idea, like a number that rest in our minds – then we have 3 more options!
**No negatives: Starting point**0, 1/4 infinity, 1/2 infinity, 3/4 infinity, infinity**Negatives:**0/Infinity, -1/4,**(Starting point) 0**, +1/4, Infinity/0**Negatives, no known starting point:**1/4 could be anything! Choose your own reference point!

*Note: I just saw this question on Quora and decided to answer it. Before doing so there, I’m doing it on my own site! I don’t like how Quora forces users to sign in to view answers the public shares. “I” intend them for anyone.