##### Wiktionary

**theoretical physics**

n. (context physics English) the description of natural phenomena in mathematical form, especially in order to derive fundamental laws of nature and to derive conclusions from these laws

##### Wikipedia

**Theoretical physics**

**Theoretical physics** is a branch of physics which employs mathematical models and abstractions of physical objects and systems to rationalize, explain and predict natural phenomena. This is in contrast to experimental physics, which uses experimental tools to probe these phenomena.

The advancement of science depends in general on the interplay between experimental studies and theory. In some cases, theoretical physics adheres to standards of mathematical rigor while giving little weight to experiments and observations. For example, while developing special relativity, Albert Einstein was concerned with the Lorentz transformation which left Maxwell's equations invariant, but was apparently uninterested in the Michelson–Morley experiment on Earth's drift through a luminiferous ether. Conversely, Einstein was awarded the Nobel Prize for explaining the photoelectric effect, previously an experimental result lacking a theoretical formulation.

#### Usage examples of "theoretical physics".

Determining whether or not information actually does get lost is one of the major questions in __theoretical physics__ today.

I found out where his room was -- in the basement of the __theoretical physics__ section, where I worked -- and I knew he worked in the evening, when the machines weren't being used.

Possibly in one or another nook there would perhaps be a dust particle or a small bubble to be examined and classified, but the system as a whole stood there fairly secured, and __theoretical physics__ approached visibly that degree of perfection which, for example, geometry has had already for centuries.

When McAndrew wasn't busy inside his head, staring at the wall in front of him and performing the mental acrobatics that he called __theoretical physics__, we talked, played and exercised.

It so happened that Meitner's nephew, Otto Frisch, who worked with Niels Bohr at Bohr's Institute of __Theoretical Physics__ in Copenhagen, had come to Sweden to spend Christmas with her, and between them they worked out what had happened.

It was thought that a similar equation would govern the proton, which was the only other particle known at the time, and that would be the end of __theoretical physics__.

He studied __theoretical physics__ and threw himself body and soul into work on entropy, a process at the heart of thermodynamics, which seemed to hold much promise for an ambitious young man.

They were professors of __theoretical physics__ from the University of Icaria, an independent research school funded by six BMs.

I devoted much time to the study of these papers, reasoning that, if the hidden event were in the realm of __theoretical physics__ rather than of political origin, then its nature might be definable from clues in the published works that followed it.

Zeno's paradoxes still show up today in some areas of __theoretical physics__ and mathematics, although Achilles and the Tortoise can be dealt with by agreeing that if space and time are both continuous, then infinitely many things can (indeed must) happen in a finite time.

Thus we had Heisenberg come to the Copenhagen Institute for __Theoretical Physics__, proposing cooperation between German and Danish science.

I had a high IQ and knew I wanted to study __theoretical physics__ by the time I was seven.

After twelve months drowning in the worst excesses of biotechnology, the pristine world of __theoretical physics__ shone in my mind's eye like some anesthetized mathematical heaven, where everything was cool and abstract and gloriously inconsequential .