Existence of four dimensions of space-time
You ask the question of Where the four dimensions of space-time are supposed to exist.
Just for a moment, forget about the big bang and the balloon effect etc.
See your eyes, they see an image in front of them and reflect the image upside down inside your head then throw the image back to your brain right side up so that you can see the image in it's proper place in front of you.
Now when you put your eyes in an upward glance when you move forward, you can see where you are going to step to and when you put your eyes down past your nose as you walk, you stumble and fall. These two places are the two most important dimensions of space-time that there is. They contain two pure energies that are in everything, the photons and the electrons. The photons exist above the electrons in front of your face and provide the different dimentions that you ask about. Light moves in an arc and light is an electric energy, so you could think about the two arcs joined together as a circle. You have been told about the above and the below differing dimentions of energies, now the other two are on the left and the right of these two dimentional energies. Imagine the form of a cross in front of your eyes and you get four dimentions and energies and lifestyles. As your eyeball moves into any one of the four energies that are in front of your pupil, your life will move into that dimention of energy. To prove my point, the right contains positive energy and the left contains negative energy and so take a hammer and holding a nail to be driven into wood, LOOK AT THE NAIL with your EYES SLANTED UPWARDS INTO THE RIGHT HIGH SIDE into the positive energy of photons. You will find that the hammer hits the nail and the nail slides easily into the wood. Now try the opposite, look at the nail while you are LOOKING DOWN at it past the LEFT SIDE END OFYOUR NOSE and do be careful, because you will hit your thumb, your fingers and miss the nail many times. You will have just entered the lower negative dimention of energy.
There really IS FOUR dimentions of space-time in the air and atmosphere and you live in all the time. As regards the big bang theory, well that will be for another time. Just try the experiment and learn about the four dimentions of energies that you cannot see but oh boy, when you know about them, you sure can feel them.