Science is a result of the human ability to perceive time and change and, an innate desire to understand the past and present, then use that understanding to predict, and hopefully, affect the future.  Science is a collection of Models which relate cause and effect.  Logic and mathematics provide structure and the language for models. 

The "definition" above is this author's perspective. 

Pure Science involves philosopy and Experimental Science involves engineering.  Science has become a mix of lofty ideas and marketing, for example, Bell's Theorem (lofty...Google it) and SmartPhones (quantum marketing).  The value of each SCIENTIFIC model below is that THEY WORK

"You can do anything you wish with the Universe, except ignore it." M. R. Neal 

Models are applied under boundary conditions which limit the range of phenomena that can be successfully described by the model.  There is a principle called Superposition which requires that the predictions of new models yield the same results as older successful models within the old boundaries.  Three physical Models are in current use to predict and describe the behavior of the observed universe. 

Newtonian Mechanics
This is the oldest model still in use.  It effectively deals with phenomena directly apparent to the five human senses and, to a limited extent, phenomena detected by older technologies.  Modern technology has allowed us to observe phenomena well outside the boundaries of our unaided senses.  These phenomena include extremely small and extremely large objects and objects moving at incredible speeds. 

Relativistic Mechanics
Albert Einstein developed the Special Relativity Model to deal with object motions and clock behavior at velocities nearing the speed of light.  His General Relativity Model extends Special Relativity to deal with gravity.  Einstein's relativity models conform to superposition because they "reduce" to Newtonian Mechanics Model formats when applied to situations well described by Newtonian Mechanics

Quantum Mechanics
This model accurately deals with phenomena under boundary conditions outside of both the Newtonian and Special Relativity models but, attempts to apply it to include part of General Relativity, specifically gravity, have proven to be very difficult.  Quantum Mechanics' validation is that it works outside the boundaries of other models.  The experimentally verified part of quantum mechanics is called the Standard Model

The Standard Model contains numerous extensions like Electrodynamics and Chromodynamics.  It also contains rules, two of which are critical when dealing with astronomical objects like White Dwarf Stars and Neutron Stars.  One is the Pauli Exclusion Principle and the other is the Heisenburg Uncertainty Principle.  Both of these principles are "rules" which prohibit certain conditions from being valid in the model.  In Quantum Mechanics, any condition is assumed to exist in nature unless it is specifically prohibited. 

Future(?) Mechanics
Einstein, Maxwell and others wondered how electricity, magnetism and light worked.  That enquiry resulted in the Relativity Models which are broadly based on force fields described mathematically as continuous functions.  Using these models, humans created analog technologies like radios.  Some devices, like photoelectric cells, were not well understood in terms of these models.  The Quantum model was developed to explain these weird digital technologies.  The mathematics used to describe the quantum model is considerably more complex than that used to describe the older models.  The big difference is that, for tiny "particles," one can only determine a "probable" location if one knows the particle's speed and direction.  If a particle's exact location is known, it's impossible to determine its speed or direction.

Light behaves like a wave, with speed and direction, when moving through space, i.e., its location is "fuzzy." ' However, it behaves like a particle when it's absorbed at a specific location.  A single particle of light, a "photon," can also be observed in two different places at the same time.  Is light a wave or a particle? 

Two different models must be used to describe these behaviors and this makes physicists very uncomfortable.  This conundrum is called the Wave-Particle Duality.  Theoretical physicists are currently working on several new models which describe this duality.  Stay tuned.