{"id":14649,"date":"2026-01-13T15:54:18","date_gmt":"2026-01-13T14:54:18","guid":{"rendered":"https:\/\/www.lapth.cnrs.fr\/?page_id=14649"},"modified":"2026-01-13T16:03:58","modified_gmt":"2026-01-13T15:03:58","slug":"what-is-theoretical-physics","status":"publish","type":"page","link":"https:\/\/www.lapth.cnrs.fr\/en\/what-is-theoretical-physics\/","title":{"rendered":"What is theoretical physics?"},"content":{"rendered":"\t\t
\n\t\t\t\t\t\t
\n\t\t\t\t\t\t
\n\t\t\t\t\t
\n\t\t\t
\n\t\t\t\t\t\t
\n\t\t\t\t\t\t\t
\n\t\t\t
<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t
\n\t\t\t
\n\t\t\t\t\t\t
\n\t\t\t\t\t\t
\n\t\t\t\t\t
\n\t\t\t
\n\t\t\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
\n\t\t\t\t\t\t
\n\t\t\t\t\t
\n\t\t\t
\n\t\t\t\t\t\t
\n\t\t\t\t\t

What is theoretical physics?<\/h2>\t\t\t\t<\/div>\n\t\t\t\t
\n\t\t\t\t\t\t\t\t\t

The goal of physics is to understand the phenomena that surround us. More precisely, we try to extract laws governing cause-and-effect relationships. For example, if you lift an object and then let it go, it falls downward. Physics allows us to highlight laws that describe how the object falls, its trajectory, and the time it takes to fall.<\/p>

To do this, physics uses theories. In the case of the example above, there are several theories of gravitation \u2014 notably Newtonian gravitation and General Relativity \u2014 which describe in different ways how bodies interact with one another.<\/p>

We call theoretical physics the sub-discipline that creates and studies these theories. All theories are expressed in a mathematical language and use mathematical tools. The part of physics that focuses on the formal aspects is called mathematical physics.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

\n\t\t\t\t\t\t
\n\t\t\t\t\t
\n\t\t\t
\n\t\t\t\t\t\t
\n\t\t\t\t\t

How do we know if a theory is valid?<\/h2>\t\t\t\t<\/div>\n\t\t\t\t
\n\t\t\t\t\t\t\t\t\t

Why are there multiple theories to describe gravitation? Before answering that question, we should first be glad that at least one exists \u2014 because there are phenomena for which we still don\u2019t have a satisfactory theory, and therefore don\u2019t understand them!<\/p>

Going back to gravitation: the Newtonian theory was proposed in the 16\u1d57\u02b0 century and allowed us to understand the trajectories of the planets around the Sun under the influence of its gravitational pull. However, certain phenomena appeared that this theory could not satisfactorily explain (for example, some anomalies in planetary motion). It was then necessary to look for another theory, which gave rise to General Relativity.<\/p>

It is experimentation that ultimately allows us to decide between the different theories that may be proposed to describe phenomena.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t

\n\t\t\t\t\t

And what about the LAPTh?<\/h2>\t\t\t\t<\/div>\n\t\t\t\t
\n\t\t\t\t\t\t\t\t\t

The scientific activities of the members of the LAPTh can be grouped into three major, interconnected themes:<\/p>