Whatthis world if Protagonist is diligently thinking her way through four dimensions. So A leads to B to C to D; but maybe there is a feeling of uneasiness external. 'I should not be here' but continuing on 'there is nothing preventing beings from sharing our three-dimensional space; and they simply have a different fourth coordinate. They can move through it at will perhaps subject to gravity. And were they to cast a shadow onto this world that shadow would appear to be three-dimensional. A dark cloud appeared behind Protagonist with this thought... and seemed to lean over her shoulder as if to study what she wrote. 'CAN'T you do any better?' Protagonist said aloud.
'You said it yourself' said the cloud, 'this is the best possible given the gravity.'
'But the earth and the sun must match up. How does this work?'
'You have an expression that captures it already. Care to guess?'
'I can't imagine.' Protagonist exerted a great deal of emotional energy to appear calm. Silence. The cloud hovered. 'You look like a charcoal scribble.'
It spoke again. 'Before you refined your language, you used to say "squirmble".'
'So you know my history? I'm not sure I like that.'
'Just a little, from a past time. I was learning myself at the time; you were my teacher. But come, do you not know the expression you have for existing in a three-dimensional space with an added fourth dimension?'
'No, I'm sorry, I remain in the dark. What is the expression?'
'The expression is: Down the rabbit hole.'