In the Beginning

What is the geometry of the Universe?

The density of matter inside the Universe determines its geometry: for a high density we will obtain a closed universe with a positive curvature, but with a density lower than the critical density, we will obtain an open universe.


Closed Universe looks like the surface of a sphere a + b + c>180^o	Flat Universe a + b + c=180^o	Open Universe looks like a horse saddle a + b + c<180o

Some scientist say that time-space is closed, and folded inside like the Swiss cheese. But recent observations show that it is flat, or better, cubic.

Moreover, the Universe accelerates its expansion and we do not know why!

Time evolution of the Universe for different mass density parameter W₀ which measures the ratio between the density r of the studied universe and a particular density, called the critical density r_c. (about 6 10-²⁷ kg/m³ ).