Physics And Its Branches 5wy1x

Physics is the scientific study of matter and energy and how they interact with each other. This energy can take the form of motion, light, electricity, radiation, gravity . . . just about anything, honestly. Physics deals with matter on scales ranging from sub-atomic particles (i.e. the particles that make up the atom and the particles that make up those particles) to stars and even entire galaxies.

How Physics Works As an experimental science, physics utilizes the scientific method to formulate and test hypotheses that are based on observation of the natural world. The goal of physics is to use the results of these experiments to formulate scientific laws, usually expressed in the language of mathematics, which can then be used to predict other phenomena.

The Role of Physics in Science In a broader sense, physics can be seen as the most fundamental of the natural sciences. Chemistry, for example, can be viewed as a complex application of physics, as it focuses on the interaction of energy and matter in chemical systems. We also know that biology is, at its heart, an application of chemical properties in living things, which means that it is also, ultimately, ruled by the physical laws. Over the years, one thing scientists have discovered is that nature is generally more complex than we give it credit for. The following laws of physics are considered fundamental, but many of them refer to idealized, closed systems, which are hard to obtain in the real world. Also, some are altered slightly in different circumstances. The laws that Newton developed, for example, are modified by the findings of the theory of relativity, but they are still basically valid in most regular cases that you'll run into.

Newton's Three Laws of Motion: Sir Isaac Newton developed the Three Laws of Motion, which describe basic rules about how the motion of physical objects change. Newton was able to define the fundamental relationship between the acceleration of an object and the total forces acting upon it.

"Law" of Gravity: Newton developed his "Law of Gravity" to explain the attractive force between a pair of masses. In the twentieth century, it became clear that this is not the whole story, as Einstein's theory of general relativity has provided a more comprehensive explanation for the phenomenon of gravity. Still, Newton's law of gravity is an accurate low-energy approximation that works for most of the cases that you'll explore in physics.

Conservation of Mass-Energy: The total energy in a closed or isolated system is constant, no matter what happens. Another law stated that the mass in an isolated system is constant. When Einstein discovered the relationship E=mc2 (in other words that mass was a manifestation of energy) the law was said to refer to the conservation of mass-energy. The total of both mass and energy is retained, although some may change forms. The ultimate example of this is a nuclear explosion, where mass transforms into energy.

Conservation of Momentum: The total momentum in a closed or isolated system remains constant. An alternative of this is the law of conservation of angular momentum.

Laws of Thermodynamics: The laws of thermodynamics are actually specific manifestations of the law of conservation of massenergy as it relates to thermodynamic processes.

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The zeroeth law of thermodynamics makes the notion of temperature possible.

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The second law of thermodynamics relates to the natural flow of heat within a closed system.

The first law of thermodynamics demonstrates the relationship between internal energy, added heat, and work within a system. The third law of thermodynamics states that it is impossible to create a thermodynamic process which is perfectly efficient.

Electrostatic Laws: Coulomb's law and Gauss's law are formulations of the relationship between electrically charged particles to create electrostatic force and electrostatic fields. The formulas, it turns out, parallel the laws of universal gravitation in structure. There also exist similar laws relating to magnetism and electromagnetism as a whole.

Invariance of the Speed of Light: Einstein's major insight, which led him to the Theory of Relativity, was the realization that the speed of light in a vacuum is constant and is not measured differently for observers in different inertial frames of reference, unlike all other forms of motion. Some theoretical physicists have conjectured different variable speed of light (VSL) possibilities, but these are highly speculative. Most physicists believe that Einstein was right and the speed of light is constant.

Modern Physics & Physical Laws: In the realm of relativity and quantum mechanics, scientists have found that these laws still apply, although their interpretation requires some refinement to be applied, resulting in fields such as quantum electronics and quantum gravity. Care should be taken in applying them in these situations. Physics is a diverse area of study and in order to make sense of it scientists have been forced to focus their attention on one or two smaller areas of the discipline. This allows them to become experts in that narrow field, without getting bogged down in the sheer volume of knowledge that exists regarding the natural world. Below is a list - by no comprehensive - of different disciplines of physics. The list will be updated with new additions and definitions as appropriate.

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Acoustics - the study of sound & sound waves Astronomy - the study of space Astrophysics - the study of the physical properties of objects in space

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Atomic Physics - the study of atoms, specifically the electron properties of the atom

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Chemical Physics - the study of physics in chemical systems

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Cosmology - the study of the universe as a whole, including its origins and evolution

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Crystallography - the study of crystals and crystalline structures

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Electronics - the study of the flow of electrons, generally in a circuit

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Geophysics - the study of the physical properties of the Earth

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High Pressure Physics - the study of physics in extremely high pressure systems, generally related to fluid dynamics

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Laser Physics - the study of the physical properties of lasers

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Mechanics - the study of the motion of bodies in a frame of reference

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Nuclear Physics - the study of the physical properties of the atomic nucleus

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Quantum Mechanics / Quantum Physics - the study of science where the smallest discrete values, or quanta, of matter and energy become relevant

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Quantum Optics - the application of quantum physics to light

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Quantum Gravity - the application of quantum physics to gravity and unification of gravity with the other fundamental particle interactions

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Relativity - the study of systems displaying the properties of Einstein's theory of relativity, which generally involves moving at speeds very close to the speed of light

Biophysics - the study of physics in living systems Chaos - the study of systems with strong sensitivity to initial conditions, so a slight change at the beginning quickly become major changes in the system Computational Physics - the application of numerical methods to solve physical problems for which a quantitative theory already exists Cryophysics / Cryogenics / Low Temperature Physics - the study of physical properties in low temperature situations, far below the freezing point of water Electromagnetism - the study of electrical and magnetic fields, which are two aspects of the same phenomenon Fluid Dynamics / Fluid Mechanics - the study of the physical properties of "fluids," specifically defined in this case to be liquids and gases High Energy Physics - the study of physics in extremely high energy systems, generally within particle physics

Mathematical Physics - applying mathematically rigorous methods to solving problems within physics Meteorology / Weather Physics - the physics of the weather Molecular Physics - the study of physical properties of molecules Nanotechnology - the science of building circuits and machines from single molecules and atoms Optics / Light Physics - the study of the physical properties of light Particle Physics - the study of fundamental particles and the forces of their interaction Plasma Physics - the study of matter in the plasma phase Quantum Electrodynamics - the study of how electrons and photons interact at the quantum mechanical level

Quantum Field Theory - the application of quantum physics to fields, including the fundamental forces of the universe

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Statistical Mechanics - the study of large systems by statistically expanding the knowledge of smaller systems

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String Theory / Superstring Theory - the study of the theory that all fundamental particles are vibrations of one-dimensional strings of energy, in a higher-dimensional universe

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Thermodynamics - the physics of heat

It should become obvious that there is some overlap. For example, the difference between astronomy, astrophysics, and cosmology can be virtually meaningless a There are a lot of interesting theories in physics. Matter exists as a state of energy, while waves of probability spread throughout the universe. Existence itself may exist as only the vibrations on microscopic, trans-dimensional strings. Here are some of the most interesting theories, to my mind, in modern physics (in no particular order, despite the enumeration).

Wave Particle Duality

Matter and light have properties of both waves and particles simultaneously. The results of quantum mechanics make it clear that waves exhibit particle-like properties and particles exhibit wave-like properties, depending on the specific experiment. Quantum physics is therefore able to make descriptions of matter and energy based on wave equations that relate to the probability of a particle existing in a certain spot at a certain time.

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Einstein's Theory of Relativity Einstein's theory of relativity is based upon the principle that the laws of physics are the same for all observers, regardless of where they are located or how fast they are moving or accelerating. This seemingly common sense principle predicts localized effects in the form of special relativity and defines gravitation as a geometric phenomenon in the form of general relativity.

Quantum Probability & the Measurement Problem Quantum physics is defined mathematically by the Schroedinger equation, which depicts the probability of a particle being found at a certain point. This probability is fundamental to the system, not merely a result of ignorance. Once a measurement is made, however, you have a definite result. The measurement problem is that the theory doesn't completely explain how the act of measurement actually causes this change. Attempts to solve the problem have lead to some intriguing theories.

Heisenberg Uncertainty Principle

The physicist Werner Heisenberg developed the Heisenberg Uncertainty Principle, which says that when measuring the physical state of a quantum system there's a fundamental limit to the amount of precision that can be achieved. For example, the more precisely you measure the momentum of a particle the less precise your measurement of its position. Again, in Heisenberg's interpretation this wasn't just a measurement error or technological limitation, but an actual physical limit.

Quantum Entanglement & Nonlocality

In quantum theory, certain physical systems can become "entangled," meaning that their states are directly related to the state of another object somewhere else. When one object is measured, and the

Schroedinger wavefunction collapses into a single state, the other object collapses into its corresponding state ... no matter how far away the objects are (i.e. nonlocality). Einstein, who called these influences "spooky action at a distance," illuminated this concept with his EPR Paradox.

Unified Field Theory Unified field theory is a type of theory that goes about trying to reconcile quantum physics with Einstein's theory of general relativity. The following are examples of specific theories that fall under the heading of unified field theory:

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Quantum Gravity

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Grand Unified Theory

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Loop Quantum Gravity

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Theory of Everything

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Supersymmetry

String Theory / Superstring Theory / M-Theory

The Big Bang

When Albert Einstein developed the Theory of General Relativity, it predicted a possible expansion of the universe. Georges Lemaitre thought that this indicated the universe began in a single point. The name "Big Bang" was given by Fred Hoyle while mocking the theory during a radio broadcast. In 1929, Edwin Hubble discovered a redshift in distant galaxies, indicating that they were receding from Earth. Cosmic background microwave radiation, discovered in 1965, ed Lemaitre's theory. More Info

Dark Matter & Dark Energy Across astronomical distances, the only significant fundamental force of physics is gravity. Astronomers find that their calculations & observations don't quite match up, though. An undetected form of matter, called dark matter, was theorized to fix this. Recent evidence s dark matter. Other work indicates that there might exist a dark energy, as well. Current estimates are that the universe is 70% dark energy, 25% dark matter, and only 5% of the universe is visible matter or energy!

Quantum Consciousness

In attempts to solve the measurement problem in quantum physics (see above), physicists frequently run into the problem of consciousness. Though most physicists try to sidestep the issue, it seems that there is a link between the conscious choice of experiment and the outcome of the experiment. Some physicists, most notably Roger Penrose, believe that current physics cannot explain consciousness, and that consciousness itself has a link to the strange quantum realm.

Anthropic Principle Recent evidence shows that were the universe just slightly different, it wouldn't exist long enough for any life to develop. The odds of a universe that we can exist in are very small, based on chance. The controversial Anthropic Principle states that the universe can only exist such that carbon-based life can arise.

The Anthropic Principle, while intriguing, is more a philosophical theory than a physical one. Still, the Anthropic Principle poses an intriguing intellectual puzzle.