Among the many mysteries of the universe there is one that is deceptively simple and yet strikes at the very heart of our ignorance of the world : what is the shape of the universe ? To hail to the right answer , we call for to solve the enigma of dark matter and dark vim and some other pretty crucial problems — and we do n’t have the tools to do that just yet .
So , for now , we have the near guess : The universe of discourse , as far as we can tell , is 3 - dimensionally two-dimensional . Now , this does n’t imply we live in Flatlandia or that somehow the Earth is plane ( it really is n’t ) . It ’s about the geometry of the cosmos , and the 2-dimensional creation has avery simple geometry , something you might have meet in math lessons in shoal : two parallel lines in this universe will never meet , and the sum of the midland angles of a triangle is always 180 degree .
The geometry of the universe is estimated from the attribute of the various components : electromagnetic radiation , even thing , dark affair , and dark vigor . If the total of all the densities of these matches a accurate turn , called the " critical density " , the universe is 2-dimensional . A value lower or high give rise very unlike geometries , as you may see below .
If the concentration of the world is less than the vital density then the shape of the macrocosm is akin to a saddle or a pringle ( if the universe was 2 - dimensional ) . In that world , two parallel lines not only never meet but mature further and further apart . This is known as an " open universe " .
On the other side of the critical concentration , there is the " closed universe " . The macrocosm in this font has a geometry that has a 2D equivalent to the surface of a sphere . This does n’t entail that the world is a openhanded orb , these are just ways for us to empathize the complexness of 4 - dimensional geometry using something we are familiar with .
In a shut universe , parallel lines meet twice . This might seem completely wrong , but it is easy to picture it . Just imagine the meridians , the lines that provide the longitude of a location on Earth . These lines are all parallel to each other at the equator . But they will converge at the North and South Pole .
So where does our best guess add up from ? Observations of the ingredient of the population tell us that it is really very close to the vital density , sovery tight to being flat , with the uncertainness being in the unsympathetic cosmos dominion . While the geometry is simple(r ) , there are a lot of forcible problems to solve this
First of all , we still do n’t know exactly whatdark matteranddark energyare , which may affect the geometry of the universe . Even if we ignore that , there are more issues to solve . For the universe to have a density very tight to the decisive denseness today , it mean that it had to beexactlythe decisive density during the Big Bang . However , there is no intellect for this to be the case .
There are scenario that work this and other problems , such ascosmic inflationbut they are yet to be experimentally confirmed . The size of the universe , if it ’s non-finite or not , depends on the frame of the universe ( among other factors ) . But that , as they say , it ’s another story .
