Tang Musun is one of the main founders of thermodynamics and has made a series of great contributions to the development of thermodynamics. According to the theories of Gay-Lussac, Kano and clapper Long, he founded the thermodynamic temperature scale in 1848. He pointed out: "The characteristic of this temperature scale is that it is completely independent of the physical properties of any special substance." This is the standard temperature scale in modern science. He is one of the two main founders of the second law of thermodynamics (the other is Clausius). In 185 1, he put forward the second law of thermodynamics: "It is impossible to absorb heat from a single heat source and make it completely useful without other influences." This is the accepted standard expression of the second law of thermodynamics. It is also pointed out that if this law is not established, it must be admitted that there can be a perpetual motion machine, which can obtain mechanical work indefinitely by cooling seawater or soil, which is the so-called second perpetual motion machine. He asserted from the second law of thermodynamics that energy dissipation is a universal trend. 1852 cooperated with Joule to further study the internal energy of gas, improved the free expansion experiment of Joule gas, conducted the porous plug experiment of gas expansion, and found Joule-Thomson effect, that is, the temperature change phenomenon caused by adiabatic expansion of gas through porous plug. This discovery has become one of the main methods to obtain low temperature and is widely used in low temperature technology. In 1856, he predicted a new thermoelectric effect in theory, that is, when current flows through a conductor with uneven temperature, the conductor will absorb or release some heat (called Tang Musun heat) in addition to generating irreversible Joule heat. This phenomenon was later called Thomson effect.

Tang Musun has made outstanding achievements in electromagnetic theory and engineering application. 1848, he invented the electric image method, which is an effective method to calculate the electrostatic field problem caused by the charge distribution of a conductor with a certain shape. He deeply studied the characteristics of the discharge oscillation of Leiden bottle, published the paper "Leiden bottle oscillation discharge" in 1853, and calculated the oscillation frequency, which made a pioneering contribution to the theoretical research of electromagnetic oscillation. He discussed the essence of electromagnetic field with mathematical method, and tried to unify electric power and magnetic force with mathematical formula. 1846 successfully completed the "moving image method of force" of electricity, magnetism and current, which is already the embryonic form of electromagnetic field theory (if we go further, we will go deep into the electromagnetic wave problem). He once wrote in his diary: "If I can re-examine the state of objects related to electromagnetism and current in a more special way, I will definitely go beyond what I know now, but that is of course something to come." His greatness lies in that he can introduce all his research results to Maxwell without reservation, and encourage Maxwell to establish electromagnetic phenomena's unified theory, which laid the foundation for Maxwell to finally complete the electromagnetic field theory.

He attaches great importance to integrating theory with practice. 1875 predicted that cities would use electric lighting, and 1879 proposed the possibility of long-distance power transmission. His ideas will come true in the future. 188 1 year, he reformed the motor and greatly improved its practical value. In electrical instruments, his main contribution is to establish accurate unit standards of electromagnetic quantities and design various precision measuring instruments. He invented mirror galvanometer (which greatly improved the measurement sensitivity), double-arm bridge, siphon recorder (which can automatically record telegraph signals) and so on, which greatly promoted the development of electric measuring instruments. According to his suggestion, the British Science Association established the Electrical Standards Committee in 186 1, which laid the foundation for the modern unit standards of electrical quantities. In engineering technology, from 65438 to 0855, he studied the signal propagation in cables and solved a series of theoretical and technical problems of long-distance submarine cable communication. After three failures and two years of research and experiment, Kelvin finally helped to install the first Atlantic submarine cable at 1858, which is a well-known work. He is good at combining teaching, scientific research and industrial application, and pays attention to cultivating students' practical working ability in teaching. At Glasgow University, he established the first extracurricular laboratory for students in Britain.

Tang Mu Sun was modest and diligent all his life, strong-willed, not afraid of failure and indomitable. Regarding the problem of dealing with difficulties, he said: "We all feel that difficulties must be faced squarely and cannot be avoided; We should keep it in mind and hope to solve it. In any case, every difficulty must have a solution, although we may not find it in life. " His spirit of unremitting struggle for the cause of science throughout his life will always be admired by future generations. 1896 at the meeting to celebrate his 50th anniversary as a professor at Glasgow University, he said, "There are two words that can best represent my struggle in scientific research in the past 50 years, and that is' failure'." This is enough to show his modesty.