Topic: physics

topics > Group: science

atoms and molecules
electricity and magnetism
electromagnetic field
general relativity
law of nature
Newtonian physics
physics as computation
quantum electrodynamics
quantum mechanics
science as mathematics
science as measurement
special relativity
statistical mechanics


Physics is the scientific study of the physical world. It is one of the fundamental sciences, and the first to be understood. It concerns the essential properties of space, time, matter, speed, frequency, energy, measurement. Geometric and mathematical descriptions predominate. Important concepts include symmetry and conservation. (cbb 4/2006)
Subtopic: what is physics up

Quote: physics is those sciences expressible in mathematical terms and measurements; wide application [»einsA5_1940]
Quote: the task of the physicist is to find the universal elementary laws from which the cosmos can be built by pure deduction
Quote: fundamental physics is like the rules of the game of nature; can thus understand the world even though its application may be much too complicated [»feynRP_1963]
Quote: mass, gravitational attraction and molecule are intrinsic features of the world; the realm of natural science
Quote: size, shape, place, adjacency, quantity, and speed are fundamental properties of material substance [»galiG_1623]
Quote: in physics we try to say things that no one knew before in a way that everyone can understand [»campNR_1919, OK]

Subtopic: hard vs. soft science up

Quote: quantum electrodynamics describes all physical phenomena except gravity, radioactivity and nuclear physics; there is no significant difference between experiment and theory [»feynRP_1985]
Quote: computer science is messy because it lacks the locality, symmetry, and invariance to scale found in physics [»hillWD_1985]
Quote: vital principles do not change the course of motion; motion is part of the pre-established order of nature [»leibGW5_1705]

Subtopic: speed up

Quote: the scientific definition of speed is the ratio of infinitesimal distance over infinitesimal time as the time gets smaller and smaller; not known to the Greeks
Quote: in Zeno's argument there is an infinite number of steps but not an infinite amount of time; instead, a derivative concerns the ratio of infinitesimals [»feynRP_1963]

Subtopic: motion up

Quote: for linear systems independent of time, there are usually a series of special motions which vary exponentially in time; the most general motion is a superposition of these special motions; e.g., vibrating systems with imaginary exponentials [»feynRP_1963]
Quote: the things that really are in the world without us, are those motions by which these seemings are caused

Subtopic: mass as energy up

Quote: the mass of a body is a measure of its energy-content; radiation of energy conveys inertia between the emitting and absorbing bodies [»einsA_1905b]
Quote: can locate energy because it is conserved locally; this agrees with energy's equivalence to mass and hence gravitational forces [»feynRP_1964]

Subtopic: mass up

Quote: mass or inertia is how hard it is to hold something which is going around in circle [»feynRP_1963]
Quote: light carries a momentum which is 1/c of its energy; from radiation pressure due to moving charges in a magnetic field [»feynRP_1963]

Subtopic: force up

Quote: the elements are of eternal stuff, linked with bonds of different strengths; unless a strong enough force encounters it, a thing stays safely as it was [»lucr_55]
Quote: potential energy (dead force) is elementary to kinetic energy (living force)
Quote: force is real; space, time, and motion are relative, a relationship [»leibGW4_1695]
Quote: the laws of motion must preserve the relative nature of motion
Quote: force should be estimated by the size of its effect instead of its motion [»leibGW_1686b]
Quote: use force to explain corporeal phenomena; size, shape, and motion are not entirely real [»leibGW_1686b]
Quote: matter is nothing but force; matter does not itself exist; we experience matter as force [»wallAR_1870, OK]
Quote: classical mechanics treats particles as discrete points in a continuous field; hence the corpuscle modifies the properties of the surrounding space [»debrL_1937]
Quote: a corpuscle is the center of an extended phenomenon; a point with spatial extension
Quote: material points are not fundamental; reality is a continuous field with regions of high energy density [»einsA4_1950]

Subtopic: friction up

Quote: the coefficient of friction is an artifact; two pieces of pure copper will stick together because the atoms get "confused", and a glass tumbler will scratch a wetted glass plate [»feynRP_1963]

Subtopic: gravity up

Quote: gravity apparently goes forever inversely as the square of the distance; i.e., the gravitational force on a spherical shell is independent of its radius
Quote: the theory of gravitation had an immense effect on science; here was a simple rule that governed the motion of the planets [»feynRP_1963]
Quote: because the force of gravity is proportional to mass, a small satellite inside a large one is perfectly balanced or weightless

Subtopic: astrophysics up

Quote: the galaxy is not a ball because of angular momentum; it must contract mostly in a plane [»feynRP_1963]

Subtopic: conservative force up

Quote: for a conservative force, the work done by moving an object does not depend on the path; i.e., kinetic energy plus potential energy is constant [»feynRP_1963]
Quote: all fundamental forces of nature appear to be conservative
Quote: at the microscopic, deepest level of physics, all forces are conservative forces
Quote: Kepler's law about equal areas in equal times is the law of conservation of angular momentum when there is no torque, i.e., the force is radial [»feynRP_1963]

Subtopic: conservation laws up

Quote: energy conservation law: if energy goes away from a region, it flows through the boundary of that region; similarly, charge conservation requires a local conservation law [»feynRP_1964]
Quote: the laws of conservation of momentum and energy hold exactly in quantum mechanics [»heisW_1927]
Quote: God conserves force but not motion [»leibGW_1686b]
Quote: perpetual motion is impossible; due to friction and the conservation of force
Quote: conservation of power; force can not be created, annihilated, or suspended [»faraM_1855, OK]
Quote: the total force of interrelated bodies is conserved as well as their total direction [»leibGW5_1705]
Quote: mechanical laws are never violated in natural motion; force and direction are always conserved

Subtopic: action up

Quote: action of one substance on another due to the inherent connections between things; the present contains the future [»leibGW_1686c]
Quote: bodies at rest stay at rest; bodies in motion stay in motion; nothing can change itself [»hobbT_1651, OK]

Subtopic: nuclear explosion up

Quote: everyone who has tried to make a nuclear explosion has succeeded on the first try [»mcphJ_1974]
Quote: what would it take to propel downtown Chicago through space at a few million miles an hour? [»mcphJ_1974]
Quote: a 1 kiloton fission device can make a 10 foot by 1000 foot hole; use for a transportation tunnel across the U.S. [»mcphJ_1974]

Subtopic: burning up

Quote: carbon attracts oxygen much more strongly than carbon and much more strongly than oxygen attracts oxygen; so burning causes great commotion which heats things up [»feynRP_1963]

Subtopic: rain up

Quote: rain from clouds is similar to laundry becoming damp with moisture from the sea [»lucr_55]
Quote: the sun evaporates water from the sea; the sea is vast, yielding much water

Related Topics up

Topic: atoms and molecules (57 items)
Topic: cosmology (17 items)
Topic: electricity and magnetism (53 items)
Topic: electromagnetic field (63 items)
Topic: entropy (14 items)
Topic: general relativity (47 items)
Topic: geology (2 items)
Topic: law of nature (28 items)
Topic: light (46 items)
Topic: Newtonian physics (79 items)
Topic: physics as computation (31 items)
Topic: quantum electrodynamics (34 items)
Topic: quantum mechanics (103 items)
Topic: science as mathematics (26 items)
Topic: science as measurement (36 items)
Topic: special relativity (73 items)
Topic: statistical mechanics (22 items)
Topic: symmetry (11 items)
Topic: time
(49 items)

Updated barberCB 3/06
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