Quarks are considered to be physical entities, but they are not directly observable as isolated particles. They are fundamental particles that are considered to be elementary and indivisible within the framework of the Standard Model of particle physics.
Quarks are believed to be point-like particles, meaning they are thought to have no size or internal structure. They are not considered to be like mini subatomic tornadoes or tiny spinning objects.
However, quarks exhibit a property known as color charge, which is associated with the strong nuclear force. Quarks come in three "colors" called red, green, and blue, and the combination of these colors leads to colorless particles such as protons and neutrons. This property of quarks is sometimes analogized as swirling or rotating "color charge," but it's important to note that this is just a mathematical representation used to describe the behavior of quarks and their interactions with other particles. The concept of "color" in particle physics is purely a mathematical construct and does not correspond to the everyday notion of color.
Due to a phenomenon called confinement, quarks are always found bound together in composite particles like protons and neutrons. They cannot be observed in isolation because the strong nuclear force becomes stronger as quarks are separated, making it energetically unfavorable to isolate a single quark. This is known as quark confinement, and it is a fundamental feature of the strong interaction.
So, while quarks are considered physical entities, their properties and behavior are described by mathematical models and theories based on experimental evidence.