Portal:Physics
From Wikipedia, the free encyclopedia
Arts · Biography · Geography · History · Mathematics · Philosophy · Science · Society · Technology
Physics is the science concerned with the discovery and understanding of the fundamental laws which govern matter, energy, space, and time. Physics deals with the elementary constituents of the universe and their interactions, as well as the analysis of systems best understood in terms of these fundamental principles. Because physics treats the core workings of the universe, including the quantum mechanical details which underpin all atomic interactions, it can be thought of as the foundational science, upon which stands the "central science" of chemistry, and the earth sciences, biological sciences, and social sciences. Discoveries in basic physics have important ramifications for all of science.
Classical physics traditionally included the fields of mechanics, optics, electricity, magnetism, acoustics and heat. Modern physics is a term normally used to cover fields which rely on quantum theory, including quantum mechanics, atomic physics, nuclear physics, particle physics and condensed matter physics. The more recent fields of general and special relativity are also usually placed within this category. Although this distinction can be commonly found in older writings, it is of limited current significance as quantum effects are now understood to be of importance even in fields previously considered purely classical.
Physics research is divided into two main branches: experimental physics and theoretical physics. Experimental physics focuses mainly on empirical research, and on the development and testing of theories against practical experiment. Theoretical physics is more closely related to mathematics, and involves generating and working through the mathematical implications of systems of physical theories, even where experimental evidence of their validity may not be immediately available.
The concept of entropy (Greek: εν (en=inside) + verb: τρέπω (trepo= to chase, escape, rotate, turn)) in thermodynamics is central to the second law of thermodynamics, which deals with physical processes and whether they occur spontaneously. Spontaneous changes occur with an increase in entropy. Spontaneous changes tend to smooth out differences in temperature, pressure, density, and chemical potential that may exist in a system, and entropy is thus a measure of how far this smoothing-out process has progressed. In contrast, the first law of thermodynamics deals with the concept of energy, which is conserved. Entropy change has often been defined as a change to a more disordered state at a molecular level. In recent years, entropy has been interpreted in terms of the "dispersal" of energy. Entropy is an extensive state function that accounts for the effects of irreversibility in thermodynamic systems.
Image: ice melting - classic example of entropy increasing described in 1862 by Rudolf Clausius as an increase in the disgregation of the molecules of the body of ice.
A rope trick is the whimsical term given by physicist Dr. John Malik to the curious lines and spikes which emanate from the fireball of a nuclear explosion just after detonation. The image is from the Tumbler-Snapper test series of 1952.
The surface of the fireball is over 20,000 kelvins and emits huge amounts of visible light radiation. The 'rope tricks' which protrude from the bottom of the fireball are caused by the heating, rapid vaporization and then expansion of the mooring cables tethering the tower supporting the nuclear bomb at the start of the test.
- ...that the fine structure constant may be 'drifting'?
- ...that lasers can be used to separate two isotopes very efficiently?
- ...that in 2007, CERN will open the world's highest energy particle accelerator, the Large Hadron Collider? (CMS detector pictured)
- ...that neutron stars are so dense that a teaspoonful would have more mass than every person on Earth?
- ...that every year, the Moon moves 3.82 cm away from Earth?
- ...that gold leaf is about 300 atoms thick?
- March 26, 2007 – Antarctic melting may be speeding up according to satellite data. (Reuters)
- March 1, 2007 – Stephen Hawking to experience weightlessness for first time. (CNN)
- February 2, 2007 – An IPCC meeting at Paris, France, ends with a report that finds a probability of 90 % or higher that human actions are creating a warming trend in the world's climate, causing global warming. (Reuters)
- 22 December 2006 – A new device detects land mines by listening for vibrations caused by directed sound waves. (New Scientist)
More physics news is available from Wikinews and the Current Events portal
- 1 April 1997 – Comet Hale-Bopp at perihelion
- 12 April 1633 – Galileo Galilei's trial starts
- 15 April 1707 – Leonhard Euler's birthday
- 18 April 1955 – Albert Einstein died
- 22 April 1904 – Robert Oppenheimer's birthday
- 24 April 1990 – Hubble Space Telescope launched
- 30 April 1777 – Carl Friedrich Gauss's birthday
- Add to Did you know, and Upcoming anniversaries.
- Add new Selected articles and Selected pictures to the queues.
- Add to Physics news.
- Expand a physics stub.
- Fix a page needing attention: Modern physics, Classical physics, Other physics topics.
- Create a requested article.
- Add a requested image.
- Help by joining WikiProject Physics. The central place for discussing physics-related issues on Wikipedia is the Project's talk page.
- Check out other physics-related WikiProjects: WikiProject Science, WikiProject Fluid dynamics, WikiProject Elements.
Fundamentals: Fundamental concepts | Constants | Physical quantities | Units of measure | Mass | Length | Time | Space | Energy | Matter | Force | Gravity | Electricity | Magnetism | Waves
Basic physics: Introductory physics | Mechanics | Electromagnetism | Statistical mechanics | Thermodynamics | Quantum mechanics | Relativity | Optics | Acoustics
Specific fields: Acoustics | Astrophysics | Atomic physics/Molecular physics/Optical physics | Computational physics | Condensed matter physics | Nuclear physics | Particle physics | Plasma physics
Tools: Detectors | Interferometry | Measurement | Radiometry | Spectroscopy | Transducers
Background: Physicists | History of physics | Philosophy of physics | Physics education | Physics journals | Physics organizations
Other: Physics in fiction | Pseudophysics | Physics lists | Physics software | Physics stubs
|
|
|
|
|
