Quote from David Hume:
The depth of either side of the inside market does not constitute volume. Lifting of the bid or ask merely confirms my point that price may lead volume.
The inside bid/ask is a location in a single dimension universe. On either side are the opposing forces of supply and demand.
The distance between the bid and ask will expand and contract depending on the amount of force behind each side.
Trades are the physical particles within this universe. Their elements are; time, price and volume. They are the byproduct of the conversion of the latent energy of supply and demand into matter and will be created whenever there is unequal amount of supply and demand present.
Entropy, the lack of trades, occurs when there is equilibrium between supply and demand.
When there is slight imbalance between the force of supply and demand matter will be generated with little or no movement within the universe. This can be considered background noise.
A minor imbalance can eventually degenerate into entropy or can create a regenerative feedback loop that attracts additional supply and/or demand to the current location.
Once a significant disparity in supply and demand exists the result is linear movement within the universe. This phenomena can be measured as the velocity and acceleration of trade particles.
If the imbalance becomes so great between supply and demand matter will cease to be created while the bid and ask spontaneously warps to a new location where matter can once again be created.
Works for me...