Without any doubt, the regularity which astronomy shows us in the movements of the comets takes place in all phenomena. The trajectory of a simple molecule of air or vapour is regulated in a manner as certain as that of the planetary orbits; the only difference between them is that which is contributed by our ignorance. Probability is relative in part to this ignorance, and in part to our knowledge.
Interpretation
This quote highlights the deterministic nature of the universe, suggesting that all phenomena follow predictable patterns, much like the orbits of celestial bodies.
In this quote, Pierre-Simon Laplace emphasizes that the certainty observed in astronomical movements extends to all aspects of nature, including the behavior of molecules. He suggests that the only true distinction between the predictable trajectories of comets and those of smaller particles lies in human ignorance, meaning that greater knowledge can lead to a clearer understanding of these phenomena. Thus, probability itself is influenced by both what we know and what we do not know.
In practice
During a lecture on the predictability of physical laws.
It is interesting thus to follow the intellectual truths of analysis in the phenomena of nature. This correspondence, of which the system of the world will offer us numerous examples, makes one of the greatest charms attached to mathematical speculations.
All the effects of Nature are only the mathematical consequences of a small number of immutable laws.
The word 'chance' then expresses only our ignorance of the causes of the phenomena that we observe to occur and to succeed one another in no apparent order. Probability is relative in part to this ignorance, and in part to our knowledge.
Given for one instant an intelligence which could comprehend all the forces by which nature is animated and the respective positions of the beings which compose it, if moreover this intelligence were vast enough to submit these data to analysis, it would embrace in the same formula both the movements of the largest bodies in the universe and those of the lightest atom; to it nothing would be uncertain, and the future as the past would be present to its eye.
The weight of evidence for an extraordinary claim must be proportioned to its strangeness.
Probability theory is nothing but common sense reduced to calculation.
A scientist is as weak and human as any man, but the pursuit of science may ennoble him even against his will.
Einstein's theory of gravitation replaced Newton's, but apples did not suspend themselves in mid-air, pending the outcome. And humans evolved from apelike ancestors whether they did so by Darwin's proposed mechanism or by some other yet to be discovered.
I hope that some day scientists can be considered heroes again, instead of Paris Hilton.
Science and mindfulness complement each other in helping people to eat well and maintain their health and well-being.
But I don't see myself as a woman in science. I see myself as a scientist.
[About the great synthesis of atomic physics in the 1920s:] It was a heroic time. It was not the doing of any one man; it involved the collaboration of scores of scientists from many different lands. But from the first to last the deeply creative, subtle and critical spirit of Niels Bohr guided, restrained, deepened and finally transmuted the enterprise.
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