It has clearly been established that matter in our universe can be viewed both as particles/objects (the Enrico Fermi point of view) or as waves in quantum fields (the Julian Schwinger point of view). How can it be both? My simple way to grasp it is to think of the universe as a big ocean in which we swim our existence. Each point of the ocean is both a particle, i.e. the drop of water presently at that spot, and a wave, i.e. the ocean is constantly in some sort of movement. What matters most in an ocean? You can focus both on its content and on its movements. There is no way to decide which is most important as they are intricately bound. In predicting the aggregate past or present of such an ocean/universe, I would think that o
the wave approach is at least as natural (if not more) than the drop approach. As an ocean constantly changes, looking at its tides, levels, etc seems to me more relevant than analyzing salinity, water color, etc.
Quantic phenomena and the uncertainty principle becomes simpler to grasp in our “ocean”. If, as it should be, each drop of water is perfectly identical to any other, how to determine the position of such a drop in a wave? We know that it cannot be determined exactly (unless we somehow tag , but then it will no longer be a simple drop of water) and we will be quite happy to have a probabilistic assessment of where it is likely to be, based among other factors on its speed and mass. If we video the area surrounding the drop and flash freeze the picture as much as we can, we will see better where the drop, maybe, but we will then lose much sense of its speed (Heisenberg’s uncertainty principle).
The existence of “dark energy” is obvious when viewing the universe as an ocean. An ocean is never fully at rest: there is always some movement that can perpetuate itself to infinity. We humans are only drops of water in that ocean and can only measure things that we can observe, i.e. that we can interfere with by proximity or by construct. We are no different than other matter in the ocean, which also observes with its own structure and affinity, but might remain “dark” to us due to a much smaller inner structure and a much more basic symmetry. Of course, an ocean has symmetry in the sense that its constituents maintain some consistency that characterizes being an ocean. Yet, each area of the ocean is fundamentally asymmetrical as perceived by the drops of water which we are.
In terms of density, is our universe really ocean-like, i.e. liquid vs. solid or gaseous? While the question is somewhat meaningless (any answer to it would be relative: our universe has to be somewhere on a density scale, right?), answering it might help generate intuitions for further investigation. To us, black holes could feel like rocks, immersed in a sea of galaxies, surrounded by an atmosphere of leptons. Applying our knowledge of rocks, oceans and gases might identify useful patterns of interaction: erosion of black holes, tornados of Big Bangs, etc.
The concept of time and space (space time) makes sense for a drop of water, as it tracks a particular trajectory with a particular momentum, but does it make sense for an ocean? If the ocean is defined as a single entity with a complex structure of bells and whistles, such as temperature, size, tides, leaving aside component details, such as drops of water, time makes less sense, certainly not the timeframe of a drop of water. Also, spacetime is generally thought of as an abstract background on which to measure location, speed, etc. While the definition makes sense for matter particles (fermions), does it make sense for force particles (bosons)? Can there be a spacetime where two different bosons can be at the same time? Pauli excludes the possibility for fermions, “real” stuff, as if, in the battle for space location, there could be only one real victor. But massless particles , hence traveling at light speed, are free of location, mostly. Lucky travelers!
Is our world continuous, as our thirst for continuity and coherence would like it to be, or truly quantized, or both? Both, in our simplified image of an ocean: continuous in the video, and quantized in the flash freeze. Since the notion of identity is challenging (to me, impossible) in structurally equivalent fermions, the world may be best represented by a continuous succession of creation and annihilation of the fermions, a stroboscopic landscape! Again, we humans like things our way, with a neat space and time structure, and, equally shocking, an identity concept! Identical things cannot be identified, even in different locations of times. I think.
As to mass, I don’t know where to even begin describing what it is! It curbs spacetime, but we don’t really know what spacetime is, if it even exists outside of our own minds. It certainly represents an interaction on fermions in the field of Higgs bosons. Being massless precludes having inertial energy, but not kinetic energy (as in photons). In a way, being massless provides “instant” buzz, burst of energy to recipient particles, almost anytime, anywhere. Massive “things” have a more complicated structure (personality!), their symmetry is more complex along several dimensions, giving them a harder and slower time interacting with others, measuring their interactions along all their axes. Their inertial energy acts as a cumbersome overhead.
“Complex, less versatile but rich in potential” would judge a wine enthusiast!