The infinite space of the Universe

General Relativity is quite important when discussing the reality of time. According to General Relativity time can be physically bent by mass. Also this is a confirmed prediction of General Relativity.Hence we have evidence that time is a physically real thing. I know of very few man made concepts that can be bent in a physically real sense.

A symmetry is basically when some change is applied to physical system and that change doesn't affect the system. The symmetry is global if the same change is applied everywhere. It is local if a different change is applied at each location. For every global symmetry there is a corresponding conservation law.
Symmetry under time translation => Conservation of energy
Symmetry under space translation => Conservation of momentum
Symmetry under rotations => Conservation of angular momentum
Symmetry under complex number rotation => Conservation of electric charge.
e.t.c. Symmetry breaking is when the laws of physics appear differently to you, due to some condition of your environment.
A very rough analogy is conservation of momentum. Momentum is always conserved, however here on earth when you throw a ball it appears to lose momentum and fall to the ground. Of course this is due to the friction with air. However having air as a background rather than truly empty space means the effective physics on earth is quite different to the true physics. Symmetry breaking is basically when some background thing (Air, a field, e.t.c.) causes physics to appear different. The Higg's field is currently in it's vacuum state. That is the state with lowest energy. This Higg's vacuum causes the electroweak force to effectively seperate. Just like air causes an effective loss of conservation of momentum. No, because electroweak symmetry is a local symmetry. Only global symmetry is associated with conservation laws. To be totally accurate however a global symmetry does get destroyed in electroweak symmetry breaking. In that case the symmetry is gone.Now might be a good time to demonstrate the power of mathematics in physics.
Let's say I have the field which describes electrons, called the dirac field. Then I say that I want this field to have a symmetry under rotations by a complex number. Further more I want this field to be symmetric under local rotations by a complex number, that is the complex number I'm rotating by can be different at each point in spacetime. Now that I demand this, I work through the mathematics and see what it implies. Basically it implies the existence of the electromagentic field.
This works with all local symmetries, so basically:Global symmetries means conservation laws.
Local symmetries means existence of a new force.To give another example local symmetry of multiplication by a 3x3 matrix implies the existence of gluons and the strong force.Edited by Son Goku, : Update and edit.

I wouldn't worry about this, we're still well within what can be explained if my previous post was understandable. This stuff I find far easier to explain than black holes and general relativity. I'll get to color in a moment. Conservation of spin is basically also derived from symmetry under rotations. If your working with classical systems symmetry under rotations implies conservation of angular momentum only. However with a quantum system symmetry under rotations implies conservation of angular momentum and spin. Basically it's the same symmetry but QM adds an extra quantity. You essentially have it.
Electromagnetic field -> Photon
Higgs field -> Higgs boson
Dirac field -> Electron. Everytime you demand that a matter field like the dirac(electron) field, be symmetric under some local symmetry, you instantly get a new force field.
How it works is that you start with the equations for the matter field on its own and then try to make the equations symmetric under the local symmetry of your choice. If you go through the maths, you will see that the only way to do this is to introduce a new field, which is a force field, like the gluon field. This process is far more natural than I'm making it sound, the field just appears automatically.*The point of this is that you know have a mathematical theorem:
Local symmetry = New force.
So physicists just started trying out local symmetries and looking at the forces they implied, to see if any of the forces were the strong nuclear force. Basically the appropriate local symmetry was multiplication by a 3x3 complex number matrix as I mentioned.By the way this study of the forces implied by local symmetries is called Yang-Mills theory. For the electroweak force the appropriate local symmetry is, without getting to technical, multiplication by a 2x2 complex number matrix.Now here is another fact. It will seem like word salad at first. If a local symmetry implies the existence of a force, the corresponding global symmetry implies conservation of the charge associated with that force.A simple example is electromagnetism. The electromagnetic fields existence is implied by local symmetry under multiplication by a complex number. Electric charge is conserved due to global symmetry under multiplication by a complex number.The strong nuclear fields existence is implied by local symmetry under multiplication by a 3x3 complex number matrix. Color charge is conserved due to global symmetry under multiplication by a 3x3 complex number matrix.*In fact it's much more mathematically natural than even physicists understood at first.Edited by Son Goku, : Small addition.

"The Second Creation" by Crease and Mann. It is honestly the only book that goes through this stuff intelligently without mathematics. Also it's a great read. If you undertand the buzzwords, like Yang-Mills as I have explained them above, you'll get even more out of it.I should correct a slight error in my previous post. The study of the forces implied by local symmetry is called gauge theory. When the local symmetry is a nice complex matix symmetry, we call it Yang-Mills theory.

It's Robert P. Crease, Professor of Philosophy, Stoney Brook university and Charles C. Mann a very good general science writer.If you've ever read Pais' "Inward Bound" it is quite similar, but less technical.

Space has two measurable properties. Its Weyl curvature and its Ricci curvature. More simply we may say it has curvature. The presence of such curvature has been measured by several satellites in orbit. Also we have evidence of such curvature from lensing of distant galaxies, where their apparent shape is distorted by the curvature.

Well first of all, it acts exactly like curvature. Secondly, the satellites in a sense directly measure the curvature of space, rather than test the effects we associate with curvature. You see there is a standard way to calculate/measure the curvature of a space/spacetime. The satellites simply carry out that procedure and have found a non-zero curvature of spacetime in the vicinity of Earth.

Matter occupies spacetime. However regions of space and matter can both posses mass.