Newton’s First Law

Every body perseveres in its state of being at rest or of moving uniformly straight forward, except insofar as it is compelled to change its state by forces impressed.

Did you ever know that after this statement, reported with minor differences by all Mechanics textbooks as Principle of Inertia, Newton added the following three examples to better explain his concept of inertial motion? In his words:

Projectiles persevere in their motions, except insofar as they are retarded by the resistance of the air and are impelled downward by the force of gravity. A spinning hoop, which has parts that by their cohesion continually draw one another back from rectilinear motion, does not cease to rotate, except insofar as it is retarded by the air. And larger bodies – planets and comets – preserve for a longer time their progressive and their circular motions, which take place in spaces having less resistance.

Apparently these examples, interpreted as casting doubts rather than light on the initial statement, were dropped by commentators and authors, including those engaged in a chauvinistic campaign against Galileo’s “circular inertia”. I.B. Cohen in the Guide to Newton’s Principia which precedes his new translation (above quote is taken from it) could not avoid the matter. He wrote :

On first encounter, these examples may seem confusing since each involves curved paths and yet the subject of the first law is uniform linear (or rectilinear) motion.

and, by mentioning the first two examples only, vaguely concludes that

… it is only the tangential or linear component that is inertial, not the curved motion.

Also E. Mach deemed convenient to skip the matter. Under this condition, did we really understand Newton’s First Law?

Newton’s Letter

Did Einstein ever read what Newton wrote to R. Bentley on February 1693? Let’s hear it again.
“… It is inconceivable that inanimate brute matter should, without the mediation of something else, which is not material, operate upon and affect other matter without mutual contact, as it must be, if gravitation in the sense of Epicurus, be essential and inherent in it. And this is one reason why I desired you would not ascribe innate gravity to me. That gravity should be innate, inherent, and essential to matter, so that one body may act upon another at a distance through a vacuum without the mediation of anything else, by and through which their action and force may be conveyed from one to another, is to me so great an absurdity, that I believe no man who has in philosophical matters a competent faculty of thinking can ever fall into it. Gravity must be caused by an agent acting constantly according to certain laws; but whether this agent be material or immaterial, I have left to the consideration of my readers. …”

(Isaac Newton: Philosophical Writings, CUP 2004, A. Janiak ed., p. 102)

MyEpigrams!

Science, too, has its own modern terrorists.

Darwinism: bodies fall down because the evolution eliminated those going up.

Sex is a male obsession. Usually females respond on demand.

Bastard!

It’s amazing how stupid are intelligent people sometimes.

Bad manners. Now Computing like Statistical Mechanics which started as an aid and ended by questioning Physics.

When something bears a proper name, be sure its discovery belongs to someone else.

Do you really think science was made from scratch in Cambridge at the end of 17th century?

Theory of Relativity depicts a world without Inertia.

At the end, nothing seems to you more universal than what is always with you.

Mozart: just a gift to all of us.

“Physical Mathematics”, unlike Mathematical Physics, is easy and quick until a negative test. Then you must restart, confused, from the very beginning.