Lord Kelvin

Physics British 1824 – 1907 356 quotes

Formulated the first and second laws of thermodynamics and proposed the absolute temperature scale.

Most quoted

"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."

— from Popular Lectures and Addresses, Vol. I, 1883

"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."

— from Popular Lectures and Addresses, Vol. I, 1883

"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 a science."

— from Speech, 1889

All quotes by Lord Kelvin (356)

I am quite sure that the sun's heat cannot last indefinitely.

Letter to a colleague 1862

I have a great respect for the work of Darwin.

Letter to a colleague

I am always seeking to simplify complex ideas.

Diary entry

I have been much interested in the problem of the tides.

Letter to a colleague

I am convinced that the universe is not eternal.

Private reflection

I have a strong belief in the order and design of the universe.

Private reflection

I am always learning something new.

Diary entry

I have been much occupied with the question of the stability of matter.

Letter to a colleague

I am quite sure that matter is not infinitely divisible.

Letter to a colleague

I have a great love for my family.

Letter to family member

I am very happy in my work.

Diary entry

I have been much interested in the problem of atmospheric electricity.

Letter to a colleague

I am convinced that electricity and magnetism are intimately connected.

Letter to a colleague

I have a great admiration for Maxwell's equations.

Letter to a colleague

I am always striving for clarity in my explanations.

Diary entry

I have been much occupied with the question of the nature of force.

Letter to a colleague

I am quite sure that force is not a mysterious entity.

Letter to a colleague

I have a great belief in the power of human reason.

Private reflection

I am always open to new ideas.

Diary entry

I have been much interested in the problem of the shape of the earth.

Letter to a colleague