I didn't mean we are made of 3D particles and that's the reason. The physical interactions that facilitate us our senses,especially basic vision is 3D is what I meant. The OP asked what does this 4D spacetime look like. I think we need to delve deeper into Quantum and Particle Science and...
Well,we can't really know what a 4 Dimensional Hyperspace "looks" like as of now. That's because we are still trapped in the three and hence the fourth isn't yet imaginable as you are asking here. The evolved natural sensory systems and all the components'/particles' interactions are in 3D...
And,Absolute Zero is possible? I don't think you can "reach" Absolute zero like that. Even if you go to the lowest possible energy states,there is always some Quantum vibrations and fluctuations as per the Heisenberg principle. In theory and principle,you cannot probably reach that point is what...
It is in all probability linked to Planck's limit which is also based on the Limit to the Speed of Light. Temperature is a resultant of Heat which itself is a form of Energy. What happens is that if you need more Energy at a point or a defined region and start bringing that region with energy...