6 Forces Are Also Caused by Particles
45
also will have a transformational effect on our civilization. The W and the Z
boson are examples of particles whose exchange leads to weak forces. Unlike
the photon and Z boson, the exchange of the W-boson changes a proton to a
neutron.
All the particles that carry new forces are believed to be bosons, named
after the legendary Indian physicist Satyendra Nath Bose (1894–1974). He
first conceived of the fundamental difference between particles with spin zero,
one, etc., as compared to particles with spin half, three half, etc. The latter are
called fermions, named after Enrico Fermi. Satyendra Nath Bose was a modest
man, who discovered the law of bosonic particles while working in Dhaka
University (what is now in Bangladesh), far from the main hub of theoretical
physics activity, which then was Europe. He sent his manuscript on the subject
by post to Albert Einstein with a letter that started with [99]:
“Respected Sir, I have ventured to send you the accompanying article for perusal
and opinion…” Einstein studied Bose’s paper and recognized the significance
and originality of his work. He translated it into German and sent it for
publication, while following it up with another paper of his own. In that paper,
he applied Bose’s idea to atoms and predicted the existence of the so-called
Bose–Einstein condensates. He sent his paper for publication in 1924, and
it was published in the Proceedings of the Prussian Academy of Science in
January 1925. The first Bose–Einstein condensate was discovered in 1995, by
Carl Weiman, Eric Cornell, and W. Ketterle, as discussed before. Bose never
received the Nobel Prize, even though half the particles in the universe are
named after him and each boson represents a new force in the universe.
The two most basic elements in our understanding of the universe are
particles with their different spins: half odd integral spin (1/2, 3/2, 5/2 . . .)
being matter, and integral spin (0, 1, 2, . . . .) being force carriers. We can call
the half odd integral particles (the fermions) the “matter particles,” and the
integral spin particles (the bosons) the “force particles.” Every bosonic particle
in principle is a force carrier. For a long time, these two different kinds of
particles were thought to belong to two different islands of objects with no
connection to each other. However, whether they are actually different or not,
in the minds of many theorists since 1970s, they have been thought to be two
shapes of the same object, and are related to each other by a very new kind of
symmetry, called supersymmetry. This is a powerful symmetry, about which
we will have very little to say in this book, but whether it is real or not, it is
a profoundly important concept, which may connect the gravitational force
with all other forces (Fig. 6.2). The theorists were pinning their hope on the
45
also will have a transformational effect on our civilization. The W and the Z
boson are examples of particles whose exchange leads to weak forces. Unlike
the photon and Z boson, the exchange of the W-boson changes a proton to a
neutron.
All the particles that carry new forces are believed to be bosons, named
after the legendary Indian physicist Satyendra Nath Bose (1894–1974). He
first conceived of the fundamental difference between particles with spin zero,
one, etc., as compared to particles with spin half, three half, etc. The latter are
called fermions, named after Enrico Fermi. Satyendra Nath Bose was a modest
man, who discovered the law of bosonic particles while working in Dhaka
University (what is now in Bangladesh), far from the main hub of theoretical
physics activity, which then was Europe. He sent his manuscript on the subject
by post to Albert Einstein with a letter that started with [99]:
“Respected Sir, I have ventured to send you the accompanying article for perusal
and opinion…” Einstein studied Bose’s paper and recognized the significance
and originality of his work. He translated it into German and sent it for
publication, while following it up with another paper of his own. In that paper,
he applied Bose’s idea to atoms and predicted the existence of the so-called
Bose–Einstein condensates. He sent his paper for publication in 1924, and
it was published in the Proceedings of the Prussian Academy of Science in
January 1925. The first Bose–Einstein condensate was discovered in 1995, by
Carl Weiman, Eric Cornell, and W. Ketterle, as discussed before. Bose never
received the Nobel Prize, even though half the particles in the universe are
named after him and each boson represents a new force in the universe.
The two most basic elements in our understanding of the universe are
particles with their different spins: half odd integral spin (1/2, 3/2, 5/2 . . .)
being matter, and integral spin (0, 1, 2, . . . .) being force carriers. We can call
the half odd integral particles (the fermions) the “matter particles,” and the
integral spin particles (the bosons) the “force particles.” Every bosonic particle
in principle is a force carrier. For a long time, these two different kinds of
particles were thought to belong to two different islands of objects with no
connection to each other. However, whether they are actually different or not,
in the minds of many theorists since 1970s, they have been thought to be two
shapes of the same object, and are related to each other by a very new kind of
symmetry, called supersymmetry. This is a powerful symmetry, about which
we will have very little to say in this book, but whether it is real or not, it is
a profoundly important concept, which may connect the gravitational force
with all other forces (Fig. 6.2). The theorists were pinning their hope on the