, born January 24, 1947) is an American theoretical physicist, the Henry Semat Professor of Theoretical Physics in the City College of New York of City University of New York, a co-founder of string field theory, a futurist, and a "communicator" and "popularizer" of science. He has written several books about physics and related topics; he has made frequent appearances on radio, television, and film; and he writes extensive online blogs and articles. He has written two New York Times best sellers, Physics of the Impossible (2008) and Physics of the Future (2011). He has hosted several TV specials for BBC-TV, the Discovery Channel, and the Science Channel. In physics or chemistry, subatomic particles are the particles smaller than an atom. There are two types of subatomic particles: elementary particles, which are not made of other particles, and composite particles. Particle physics and nuclear physics study these particles and how they interact.
The elementary particles of the Standard Model include:
Six "flavors" of quarks: up, down, bottom, top, strange, and charm;
Six types of leptons: electron, electron neutrino, muon, muon neutrino, tau, tau neutrino;
Twelve gauge bosons (force carriers): the photon of electromagnetism, the three W and Z bosons of the weak force, and the eight gluons of the strong force;
The Higgs boson.
height and width not affected. In mathematics and theoretical physics, an invariant is a property of a system which remains unchanged under some transformation.
In a Euclidean space, the separation between two points is measured by the distance between the two points. The distance is purely spatial, and is always positive. In spacetime, the separation between two events is measured by the invariant interval between the two events, which takes into account not only the spatial separation between the events, but also their temporal separation. The interval, s2, between two events is defined as:
where c is the speed of light, and Δr and Δt denote differences of the space and time coordinates, respectively, between the events. (Note that the choice of signs for above follows the space-like convention (−+++). Other treatments reverse the sign of .)
PHYSICS CHEMISTRY BIOLOGY HISTORY
About 13 billion years ago, matter,
energy, time, and space, came into being
in what is known as The Big Bang.
The story of this fundamental features of
our universe is called physics.
Physics examines how matter, energy,
time, and space interact with one another
About 300,000 years after their
appearance matter and energy started to
combine into complex structures
which we call atoms.
And these atoms then combined into even
more complex structures which are called
The story of atoms, molecules, and their
interactions is called chemistry.
Chemistry examines what happens when an
oxygen atom comes into contact with a
hydrogen atom or when a solid molecule
comes into contact with a water molecule.
This is what chemistry does.
About 4 billion years ago on a planet
called earth certain molecules combined
to form even larger and more complex
structures which we call organisms, or
The story of organisms is biology.
About 70,000 years ago, organisms
belonging to a very particular specie,
our species, Homo sapiens started to come
together and combine and form even more
elaborate structures, which we call
The development of these human cultures
Experiment attmepteing to,provemthat light was transmitted via an aether. Experiment predicted that as the earth rotated around the sun light would chqnge speeds as a result of the earth going with or transverse to the sun/light. But there was no difference, thus, no aether.
Later, Einstein's theory of relativity proved light always moved at the same speed.
Physics theories of the late 19th century assumed that just as surface water waves must have a supporting substance, i.e. a "medium", to move across (in this case water), and audible sound requires a medium to transmit its wave motions (such as air or water), so light must also require a medium, the "luminiferous aether", to transmit its wave motions. Because light can travel through a vacuum, it was assumed that even a vacuum must be filled with aether. Since the speed of light is so great, and as material bodies pass through the aether without obvious friction or drag, the aether was assumed to have a highly unusual combination of properties.