325 years ago on the 5th July
1687, the Philosophiæ Naturalis Principia Mathematica (Latin
for "Mathematical Principles of Natural Philosophy", often referred
to as simply the Principia)
a work in three books by Sir Isaac Newton, was first published. After annotating and correcting his personal copy
of the first edition, Newton also published
two further editions, in 1713 and 1726. The Principia
states Newton’s laws of motion, forming the foundation of classical mechanics,
also Newton’s law of universal gravitation, and a derivation of Kepler’s laws
of planetary motion (which Kepler first obtained empirically). The Principia
is "justly regarded as one of the most important works in the history of
science".
The
quantity of matter is that which arises conjointly from its density and
magnitude. A body twice as dense in double the space is quadruple in quantity.
This quantity I designate by the name of body or of mass.
This was then used to define
the "quantity of motion" (today called momentum), and the principle
of inertia in which mass replaces the previous Cartesian notion of intrinsic
force. This then set the stage for the introduction of forces through the
change in momentum of a body. Curiously, for today's readers, the exposition
looks dimensionally incorrect, since Newton does not introduce the dimension of
time in rates of changes of quantities.
He defined space and time
"not as they are well known to all". Instead, he defined "true"
time and space as "absolute" and explained:
Only
I must observe, that the vulgar conceive those quantities under no other
notions but from the relation they bear to perceptible objects. And it will be
convenient to distinguish them into absolute and relative, true and apparent,
mathematical and common. [...] instead of absolute places and motions, we use
relative ones; and that without any inconvenience in common affairs; but in
philosophical discussions, we ought to step back from our senses, and consider
things themselves, distinct from what are only perceptible measures of them.
As it happens, 325 years on, on the 4th
July 2012, another matter, about mass and matter arose.
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In the Standard Model of particle
physics, the Higgs boson is a
hypothetical elementary particle, a boson, that is the quantum of the Higgs
field. The field and the particle provide a testable hypothesis for the origin
of mass in elementary particles. In popular culture, the Higgs boson is also
called the God particle, after
the title of Nobel physicist Leon Lederman’s The God Particle: If the Universe is the Answer, What is the Question?
(1993), which contained the author’s assertion that the discovery of the
particle is crucial to a final understanding of the structure of matter.
The existence of the Higgs boson was
predicted in 1964 to explain the Higgs mechanism—the mechanism by which
elementary particles are given mass.
On 4 July 2012, the two main experiments
at the LHC (ATLAS and CMS) both reported independently the confirmed existence
of a previously unknown particle with a mass of about 125 GeV/c2
(about 133 proton masses, on the order of 10-25 kg), which is
"consistent with the Higgs boson" and widely believed to be the Higgs
boson. They acknowledged that further work would be needed to confirm that it
is indeed the Higgs boson and not some other previously unknown particle
(meaning that it has the theoretically predicted properties of the Higgs boson)
and, if so, to determine which version of the Standard Model it best supports.
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