The Physics Portal

Physics (from Greek φυσική / physikê meaning science of nature) is the science concerned with the discovery and understanding of the laws of principles which govern the physical universe. Physics deals with the elementary constituents of the universe and their interactions. Therefore, it can be thought of as a 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.

Physics, like all the sciences, is a work in progress. Experimental and theoretical physics researchers continue to find new phenomena and to create and refine new models and theories.

As the fundamental science its biggest and even main goal is to bring one unified theory to the universe ^{citation needed}.

Selected article

Light cone in 2D space plus a time dimension.

A Light cone is the path that a flash of light, emanating from a single event E (localized to a single point in space and a single moment in time) and traveling in all directions, would take through spacetime. Imagine the light confined to a two-dimensional plane, the light from the flash spreads out in a circle after the event E occurs—and when graphed the growing circle with the vertical axis of the graph representing time, the result is a cone, known as the future light cone (some animated diagrams depicting this concept can be seen here). The past light cone behaves like the future light cone in reverse, a circle that contracts in radius at the speed of light until it converges to a point at the exact position and time of the event E. In reality, there are three space dimensions, so the light would actually form an expanding or contracting sphere in 3D space rather than a circle in 2D, and the light cone would actually be a four-dimensional shape. However, the concept is easier to visualize with the number of spatial dimensions reduced from three to two.

Because signals and other causal influences cannot travel faster than light in relativity, the light cone plays an essential role in defining the concept of causality. For a given event E, the set of events that lie on or inside the past light cone of E would also be the set of all events that could send a signal that would have time to reach E and influence it in some way. For example, at a time ten years before E, if we consider the set of all events in the past light cone of E that occur at that time, the result is a sphere with a radius of ten light-years centered on the future position E will occur. So, any point on or inside the sphere could send a signal moving at the speed of light or slower that would have time to influence the event E, while points outside the sphere at that moment would not be able to have any causal influence on E. Likewise, the set of events that lie on or inside the future light cone of E would also be the set of events that could receive a signal sent out from the position and time of E. Events that lie neither in the past or future light cone of E cannot influence or be influenced by E in relativity.

Selected picture

Simulated view of a black hole in front of the Large Magellanic Cloud. The ratio between the black hole Schwarzschild radius and the observer distance to it is 1:9. Of note is the gravitational lensing effect known as an Einstein ring, which produces a set of two fairly bright and large but highly distorted images of the Cloud as compared to its actual angular size.

Did you know...

• ...that in the Large Hadron Collider (LHC) (pictured) protons, accelerated to the energy of 8 TeV, move at 99.999999% of light speed and become 7,000 times (on grounds of mathematical calculations) heavier than at rest?
• ...that, at a speed of 299,792,458 m/s, light can travel to the Moon in 1.2 seconds?
• ...that the submarine telescope ANTARES, intended to detect neutrinos, may also be used to observe bioluminescent plankton and fish?
• ...that lasers can be used to separate two isotopes very efficiently?
• ...that neutron stars are so dense that a teaspoonful (5 mL) would have ten times the mass of all human world population?
• ...that every year, the Moon moves 3.82 cm away from Earth?
• ...that gold leaf is about 500 atoms thick?

Suggest a fact

Physics news

• October 29, 2009 - Results from the Fermi Gamma-ray Space Telescope indicate that "either that space-time is smooth and continuous, as general relativity proposed, or that the grains of space-time are smaller than we ever thought possible, and are having only the most minuscule effect on light waves". Discovery
• October 28, 2009 - NASA's Ares I-X rocket is sucessfully test launched from Kennedy Space Center LC-39B.
• November 7, 2008 - Physicists revisited hydrogen production experiment, performed by Italian scientist G. D. Botto in 1833 (PhysOrg.com)
• September 10, 2008 - The first particle beam is successfully steered around the Large Hadron Collider accelerator ring at CERN near Geneva, Switzerland.
• May 1, 2008 - A team of nanoscientists have grown twisted nanowires that look like pine trees by twisting the original wire from which the trees were grown. (Science, [1] [2])
• April 13, 2008 - John Wheeler died aged 96. "For me, he was the last Titan, the only physics superhero still standing." (Max Tegmark, New York Times)
• December 11, 2007 - NASA's voyager 2 probe's recent measurements prove that the solar system is asymmetrical. Several scientists suggest that this is caused by galactic magnetic fields. (CNN)
• November 24, 2007 - Speculation about space based solar power plants continues, and with oil prices rising, they might be economical too. (New Scientist)

More physics news is available from Wikinews and the Current Events portal

March anniversaries

• 1 March 1966 – first spacecraft crash-lands on Venus
• 14 March 1879 – Albert Einstein's birthday
• 20 March 1942 - Gabriele Veneziano's Brithday
• 24 March 1993 – Comet Shoemaker-Levy 9 discovered

Things you can do

Summary

• Edit a physics article

Whether you are an expert or a novice, be bold, improve an article by editing it. Practice in the sandbox if you must. But hurry back to fix that glaring error that has been bothering you.

• Join WikiProject Physics.
  • Watch the WikiProject Physics talk page for physics-related issues on Wikipedia.
• Improve Physics Portal
  • Add to Did you know, and Upcoming anniversaries.
  • Add new Selected articles and Selected pictures to the queues.
  • Add to Physics news.
• Review articles
  • Assign importance and quality to unassessed articles (See Physics quality control)
  • Review an article for techno babble and report confusing sections in articles talk page. (Give enough detail to help the editors.)
• Advanced Editing
  • Expand a physics stub.
  • Fix a page needing attention: Modern physics, Classical physics, Other physics topics.
  • Create a requested article.
• Add a requested image.
• Check out other physics-related WikiProjects: WikiProject Science, WikiProject Fluid dynamics, WikiProject Elements.

Check list for physics novices and experts new to wikipedia

• Edit a physics article

Whether you are an expert or a novice, be bold, improve an article by editing it. Practice in the sandbox if you must. But hurry back to fix that glaring error that has been bothering you.

• Register with wikipedia for a user name. (See the username policy)
• Visit the help page
• Add articles to your watch list.
• Check your watchlist on regular basis
• Revert an obvious vandalism edit
• Edit your user page to tell wikipedia enough about you to help other editors get to know you
• Review an article and make a useful comment on the talk page
• Add your name to the WikiProject Physics members list

Activities for physics novices and experts familiar with wikipedia

• Edit a physics article
• Add your name to the WikiProject Physics members list
• Revert Vandalism
• Add or improve diagrams and figures
• Assign importance and quality to unassessed articles (See Physics quality control)
• Review article for techno babble and suggest areas that need improving on talk page (or add clean up tag.)
• Fix a page needing attention: Modern physics, Classical physics, Other physics topics.

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