Top 40 Lord Kelvin Quotes (2025 Update)

1. “If you cannot measure it, you cannot improve it.”

— Lord Kelvin

Featured in: Performance Quotes, Efficiency Quotes, Progress Quotes, Engineering Quotes

2. “To measure is to know.”

— Lord Kelvin

Featured in: Engineering Quotes, Statistics Quotes

3. “In science there is only physics; all the rest is stamp collecting.”

— Lord Kelvin

4. “There is nothing new to be discovered in physics now. All that remains is more and more precise measurement.”

— Lord Kelvin

5. “When you can measure what you are speaking about, and express it in numbers, you know something about it.”

— Lord Kelvin

6. “Fourier is a mathematical poem.”

— Lord Kelvin

7. “If you study science deep enough and long enough, it will force you to believe in God.”

— Lord Kelvin

8. “Heavier-than-air flying machines are impossible.”

— Lord Kelvin

9. “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.”

— Lord Kelvin

10. “When you are face to face with a difficulty, you are up against a discovery.”

— Lord Kelvin

11. “Quaternions came from Hamilton after his really good work had been done, and though beautifully ingenious, have been an unmixed evil to those who have touched them in any way.”

— Lord Kelvin

12. “I have no satisfaction in formulas unless I feel their numerical magnitude.”

— Lord Kelvin

13. “If we can’t express what we know in the form of numbers, we really don’t know much about it.”

— Lord Kelvin

14. “Large increases in cost with questionable increases in performance can be tolerated only in race horses and fancy women.”

— Lord Kelvin

15. “Ether is the only substance we are confident of in dynamics. One thing we are sure of and that is the reality and substantiality of the luminferous ether.”

— Lord Kelvin

16. “The more thoroughly I conduct scientific research, the more I believe that science excludes atheism.”

— Lord Kelvin

17. “Can you measure it? Can you express it in figures? Can you make a model of it? If not, your theory is apt to be based more upon imagination than upon knowledge.”

— Lord Kelvin

18. “Mathematics is the only true metaphysics.”

— Lord Kelvin

19. “You know only insofar as you can measure.”

— Lord Kelvin

20. “Do not imagine that mathematics is harsh and crabbed, and repulsive to common sense. It is merely the etherealisation of common sense.”

— Lord Kelvin

21. “Let nobody be afraid of true freedom of thought. Let us be free in thought and criticism; but, with freedom, we are bound to come to the conclusion that science is not antagonistic to religion, but a help to it.”

— Lord Kelvin

22. “Fourier’s theorem is not only one of the most beautiful results of modern analysis, but it may be said to furnish an indispensable instrument in the treatment of nearly every recondite question in modern physics.”

— Lord Kelvin

23. “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.”

— Lord Kelvin

24. “To live among friends is the primary essential of happiness.”

— Lord Kelvin

25. “I believe that the more thoroughly science is studied, the further does it take us from anything comparable to atheism.”

— Lord Kelvin

26. “I can never satisfy myself until I can make a mechanical model of a thing. If I can make a mechanical model, I can understand it. As long as I cannot make a mechanical model all the way through I cannot understand.”

— Lord Kelvin

27. “The atheistic idea is so nonsensical that I do not see how I can put it in words.”

— Lord Kelvin

28. “Science is bound, by the everlasting vow of honour, to face fearlessly every problem which can be fairly presented to it.”

— Lord Kelvin

29. “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.”

— Lord Kelvin

30. “Vortices of pure energy can exist and, if my theories are right, can compose the bodily form of an intelligent species.”

— Lord Kelvin

31. “I have not had a moment’s peace or happiness in respect to electromagnetic theory since November 28, 1846. All this time I have been liable to fits of ether dipsomania, kept away at intervals only by rigorous abstention from thought on the subject.”

— Lord Kelvin

32. “The only census of the senses, so far as I am aware, that ever before made them more than five, was the Irishman’s reckoning of seven senses. I presume the Irishman’s seventh sense was common sense; and I believe that the possession of that virtue by my countrymen-I speak as an Irishman.”

— Lord Kelvin

33. “When you cannot measure, your knowledge is meager and unsatisfactory.”

— Lord Kelvin

34. “I have not the smallest molecule of faith in aerial navigation other than ballooning, or of the expectation of good results from any of the trials we heard of. So you will understand that I would not care to be a member of the Aeronautical Society.”

— Lord Kelvin

35. “The fact that mathematics does such a good job of describing the Universe is a mystery that we don’t understand. And a debt that we will probably never be able to repay.”

— Lord Kelvin

36. “There cannot be a greater mistake than that of looking superciliously upon practical applications of science. The life and soul of science is its practical application...”

— Lord Kelvin

37. “Nothing can be more fatal to progress than a too confident reliance on mathematical symbols; for the student is only too apt to take the easier course, and consider the formula not the fact as the physical reality.”

— Lord Kelvin

38. “At what time does the dissipation of energy begin?”

— Lord Kelvin

39. “Questions of personal priority, however interesting they may be to the persons concerned, sink into insignificance in the prospect of any gain of deeper insight into the secrets of nature.”

— Lord Kelvin

40. “There is nothing in science which teaches the origin of anything at all.”

— Lord Kelvin