What is Spacetime? I think this is an essential question in Cosmology. Some will accept, others don't. Has spacetime a hidden property, is it a sub-material elastic object/background or ...? Is there one spacetime or are there spacetimes? Is spacetime the "Field" (das Feld) Einstein referred to? The Stanford link http://plato.stanford.edu/entries/spacetime-holearg/ shows some approaches. Marcus pointed out in post https://www.physicsforums.com/showpost.php?p=588977&postcount=7 - referring to an article with Renate Loll - that: "According to Einstein, spacetime is flexible (malleable, ductile), but also at the same time continuous and smooth-----for example it does not have breaks (fractures, gaps, rips....)". So: 1. Flexible (thus elastic), 2. Continuous and smooth, 3. No breaks (non-breakable). In my speculative opinion spacetime is indeed a hidden object and it is non-breakable. But how can we come from these properties to local, discrete packages (which seems independent)? Well, by bending and penetrating parts of spacetime with each other you can create locally discrete zones (holons) where two or more parts of that object interact - and influence - each other. That creates locally friction (and kinetics effects) between the spacetime layers. Interaction in such system is a feedback approach: The local parts influence the larger hidden system and the hidden system influences the local packages. The consequence of this approach is that we can not make a distinction between matter (fields) and energy (fields) because they all come from the same properties. Interconnectedness in incorporated in everything, and that's called "gravity". Our Universe is thus "restructured gravity'. Attached image shows you the basic concept of the multi-layers spacetime. If the image is not loaded you can find that on this link http://mu6.com/holons_2/genderless_to_duality.jpg . But ... what is spacetime in your opinion?