Physical quantities and SI units

[2020-05-14] I included this page today in order to explain "latitude" and "longitude". I notice that the text of this page is too brief. I plan to revise it.

Dimensions of space

Dimension of space, dimension of physical quantities ... different concept.

We live in 3-dimensional space, or 4-dimensional space-time.

3-dimensional space: position of a point can be expressed in 3 real numbers.

Explanation of latitude and longitude

The shape of the earth is approximated by a sphere (Not very precise).

Latitude ("lat") of point P, in a cross section of the earth, which includes point P and both poles


Longitude ("lon") of point P, in a view of the earth from the north pole


Unit of spatial dimensions

Unit of time

Concepts of "weight" and "mass"

Primitive concept "weight", "heavy"

differentiated scientific concepts "gravity", "mass", "density"

Basic roles of mass in physical sciences

SI unit of mass and force

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