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6th Feb 2016

> How can scientists know what properties higher dimensions have?

They don't, although a few hypothesis have been presented. Dimensional research is a maths field.

> Also, what properties do the 4th-6th dimensions have?

They're *mathematical* properties. The second and third dimensions can obviously be used to represent aspects of our universe, but it's unclear if other dimensions actually represent any part of this universe. Mathematical models can be designed to describe as many, or as few dimensions as one likes, regardless of whether or not they actually represent any aspect of *this* universe in any meaningful way. There's an interesting article on higher dimensions here that you may find insightful.

> I've heard that the 4th dimension is time. Is this true?

Minkowski space, a popular mathematical physics model, treats time as the fourth dimension. But this model isn't proven to be an accurate representation of our universe, it's merely convenient for explaining a limited range of phenomena. There are alternatives which do not treat time as a dimension at all, such as the mathematical models designed by Amrit Sorli and Davide Fiscaletti.

**EDIT:** There's a book, Modern Mathematical Models of Time and their Applications to Physics and Cosmology, which contains a number of lectures and papers on *several* mathematical models which can be used to describe time, ranging from Quaternion algebra to pencil of conics. I have yet to read it -- and honestly I probably never will -- but if you're genuinely interested in mathematical models that describe time it seems like a good place to start.

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