Ah, Physics. Physics can explain anything. Scientists could prove that an elephant hanging over a cliff could be supported by its tail being wrapped around a daisy. Anyway:
Tar existing in 4 dimensions wouldn't necessarily control all tar in the world. Go read Flatland, then imagine a 3 dimensional object interacting with a 2 dimensional plane. As you pass the object through the 2 dimensional plane, its appearance in 2 dimensions will change. However, since it's only one object, it has limited size.
Similarly, a 4 dimensional object in a 3 dimensional area would appear to change size, but would still have limited size in 4 dimensions. After all, it must be located somewhere.
The real question is "
how could removing an entire section of tar not connected to the Tar Mother be productive?"
After all, the Mother could just move more of itself in to the room again in the same place, thus defeating the purpose of removing it in the first place.
For the tar growth, I think it's much more likely that Tar Mothers just perceive time faster than we do. After all, we have two or three growth spurts in the first 18 years of our lives, where we seem to just expand. If this were accelerated, we might seem to inexplicably grow every 30 turns too. Maybe it takes its nutrition from the trace elements in the air?
Since the Tar Mother is sentient (to some degree), it seems reasonable that it has highly developed psychic abilities that allow it to control similar substances, explaining how separated tar grows as well. Then, the Tar Mother could psychically pass enough instinct to its Tar Babies so they can survive on their own.
And just for the record, I fully know that oversized snakes would barely be able to move, let alone climb trees.
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