We live in a 3-dimensional world with time, but what even is a dimension? I've often heard that anything can be a dimension because the math works either way. If this was true then why is finding the dimensions needed for string theory hard?
Is a dimension something you can travel through? Is it the stacking of existing dimensions? Like how two dimensions are just one dimension stacked in another direction and 3D is just 2D stacked upwards. And time is just a moment within these dimensions stacked on each other.
In all what I would like to know is:
What is the definition of a dimension?
If anything can be a dimension then why is it hard to find dimensions needed for string theory?
