William Thomson, 1st Baron Kelvin Quotes

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A perfect thermo-dynamic engine is such that, whatever amount of mechanical effect it can derive from a certain thermal agency; if an equal amount be spent in working it backwards, an equal reverse thermal effect will be produced.

William Thomson, 1st Baron Kelvin
I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science, whatever the matter may be.

William Thomson, 1st Baron Kelvin
Symmetrical equations are good in their place, but 'vector' is a useless survival, or offshoot from quaternions, and has never been of the slightest use to any creature.

William Thomson, 1st Baron Kelvin
Simplification of modes of proof is not merely an indication of advance in our knowledge of a subject, but is also the surest guarantee of readiness for farther progress.

William Thomson, 1st Baron Kelvin
It is conceivable that animal life might have the attribute of using the heat of surrounding matter, at its natural temperature, as a source of energy for mechanical effect.... The influence of animal or vegetable life on matter is infinitely beyond the range of any scientific enquiry hitherto entered on. Its power of directing the motions of moving particles, in the demonstrated daily miracle of our human free-will, and in the growth of generation after generation of plants from a single seed, are infinitely different from any possible result of the fortuitous concurrence of atoms.

William Thomson, 1st Baron Kelvin
I am afraid I am not in the flight for aerial navigation. I was greatly interested in your work with kites; but I have not the smallest molecule of faith in aerial navigation other than ballooning or of expectation of good results from any of the trials we hear of. So you will understand that I would not care to be a member of the aëronautical Society.

William Thomson, 1st Baron Kelvin
When you are face to face with a difficulty, you are up against a discovery.

William Thomson, 1st Baron Kelvin
To live among friends is the primary essential of happiness.

William Thomson, 1st Baron Kelvin
When 'thermal agency' is thus spent in conducting heat through a solid, what becomes of the mechanical effect which it might produce? Nothing can be lost in the operations of nature—no energy can be destroyed.

William Thomson, 1st Baron Kelvin
If the water flow down by a gradual natural channel, its potential energy is gradually converted into heat by fluid friction, according to an admirable discovery made by Mr Joule of Manchester above twelve years ago, which has led to the greatest reform that physical science has experienced since the days of Newton. From that discovery, it may be concluded with certainty that heat is not matter, but some kind of motion among the particles of matter; a conclusion established, it is true, by Sir Humphrey Davy and Count Rumford at the end of last century, but ignored by even the highest scientific men during a period of more than forty years.

William Thomson, 1st Baron Kelvin
There cannot be a greater mistake than that of looking superciliously upon the practical applications of science. The life and soul of science is its practical application; and just as the great advances in mathematics have been made through the desire of discovering the solution of problems which were of a highly practical kind in mathematical science, so in physical science many of the greatest advances that have been made from the beginning of the world to the present time have been made in earnest desire to turn the knowledge of the properties of matter to some purpose useful to mankind.

William Thomson, 1st Baron Kelvin
It is impossible for a self-acting machine, unaided by any external agency, to convey heat from one body to another at a higher temperature.

William Thomson, 1st Baron Kelvin
Although mechanical energy is indestructible, there is a universal tendency to its dissipation, which produces throughout the system a gradual augmentation and diffusion of heat, cessation of motion, and exhaustion of the potential energy of the material Universe.

William Thomson, 1st Baron Kelvin
It is impossible by means of inanimate material agency to derive a mechanical effect from a portion of matter by cooling it below the temperature of the coldest surrounding bodies.

William Thomson, 1st Baron Kelvin
Tesla has contributed more to electrical science than any man up to his time.

William Thomson, 1st Baron Kelvin
I need scarcely say that the beginning and maintenance of life on earth is absolutely and infinitely beyond the range of sound speculation in dynamical science.

William Thomson, 1st Baron Kelvin
When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meager and unsatisfactory kind: it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science.

William Thomson, 1st Baron Kelvin
We may consequently regard it as certain that, neither by natural agencies of inanimate matter, nor by the operations arbitrarily effected by animated Creatures, can there be any change produced in the amount of mechanical energy in the Universe.

William Thomson, 1st Baron Kelvin
There is at present in the material world a universal tendency to the dissipation of mechanical energy.

William Thomson, 1st Baron Kelvin
Considering it as thus established, that heat is not a substance, but a dynamical form of mechanical effect, we perceive that there must be an equivalence between mechanical work and heat, as between cause and effect.

William Thomson, 1st Baron Kelvin
The hypothesis that life originated on this earth through moss-grown fragments from the ruins of another world may seem wild and visionary; all I maintain is that it is not unscientific.

William Thomson, 1st Baron Kelvin
One thing we are sure of... and that is the reality and substantiality of the luminiferous ether.

William Thomson, 1st Baron Kelvin