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critical mass

 

n.
  1. The smallest mass of a fissionable material that will sustain a nuclear chain reaction at a constant level.
  2. The amount of matter needed to generate sufficient gravitational force to halt the current expansion of the universe.
  3. An amount or level needed for a specific result or new action to occur: "The sudden national uproar over drugs and drug abuse has reached politically critical mass in Washington" (Tom Morganthau).

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The amount of fissile material (uranium-233, uranium-235, or plutonium-239) that supports a self-sustaining nuclear chain reaction. Critical mass is a definitive feature of nuclear reactors and nuclear explosives. It is increased by the presence of such neutron-absorptive materials as admixed uranium-238, aluminum pipes for flow of coolant, zirconium fuel-element cladding, and boron, cadmium, or gadolinium control rods. It is reduced by a moderator, such as graphite, heavy water, or light water, which slows down the neutrons, inhibits their escape, and thus improves the probability of producing fission in the fuel. Without a moderator, natural uranium cannot reach criticality.

Critical mass also depends on the density of the fissile component, its geometry, and the immediate surroundings. In a reactor the critical mass is not a static quantity because specific nuclear phenomena activate and influence the chain reaction. See also Nuclear reactor.

An explosive, supercritical condition can be deliberately created by rapid introduction of reactivity in excess of the requirements for a critical mass. This is the basis for nuclear explosions, which rely on sudden explosively driven densification of a subcritical fissile component. See also Atomic bomb; Hydrogen bomb; Nuclear explosion.


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Critical Mass Inc.

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Critical Mass Inc.
402 - 11 Ave. SE
Calgary, Alberta T2G 0Y4, Canada
Tel. 403-262-3006
Fax 403-262-7185

Type: Private
On the web: http://www.criticalmass.com

This agency is ready to help businesses in critical need of online marketing services. Critical Mass is a leading interactive marketing agency with about a half dozen offices in the US, Canada, and Europe. Working with such clients as Mercedes-Benz USA, Global Hyatt, Montres Rolex, and Procter & Gamble, the agency offers creative design services for corporate branding Web sites and other multimedia campaigns, as well as strategic planning and campaign management services. In addition, Critical Mass provides expertise in e-mail marketing, emerging media, and search engine optimization. The agency is 52%-owned by global advertising services conglomerate Omnicom Group; employees own the remaining 48%.

Officers:
Chairman: Jerry Johnston
CEO: Dianne Wilkins
President: Chris Gokiert

Competitors:
Blast Radius Inc.
Digitas
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the size or scale at which a business activity acquires self-sustaining viability.

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A very important or crucial stage in a company's development, where the business activity acquires self-sustaining viability. When a company reaches critical mass, it is thought that they can remain viable without having to add any more investment.

Investopedia Says:
This term is derived from nuclear physics, where critical mass is defined as the smallest mass of material that can sustain a nuclear reaction at a constant level. When compared to the financial definition, we see the similarities – being self-sustaining is the goal.

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(DOD) The minimum amount of fissionable material capable of supporting a chain reaction under precisely specified conditions.

In physics, the amount of material that must be present before a chain reaction can sustain itself.

  • The term critical mass is used to refer generally to the minimum amount of something needed to produce a given effect: “The town needs a critical mass of industry to attract more business.”
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    Critical Mass

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    San Francisco Critical Mass, April 29, 2005.

    Critical Mass is a cycling event typically held on the last Friday of every month in over 300 cities around the world.[1] The ride was originally founded in 1992 in San Francisco.[2] The purpose of Critical Mass is not usually formalized beyond the direct action of meeting at a set location and time and traveling as a group through city or town streets on bikes. Some bigger scale events as in Budapest, Hungary, have an activist group formed around it, organizing the rides and communicating the desires and problems of the cyclists to the city council.

    Critical Mass rides have been perceived as protest and intimidation activities. A 2006 New Yorker magazine article described Critical Mass' activity in New York City as "monthly political-protest rides", and characterized Critical Mass as a part of a social movement;[3] and the UK e-zine Urban75, which advertises as well as publishes photographs of the Critical Mass event in London, describes this as "the monthly protest by cyclists reclaiming the streets of London."[4] Critical Mass participants have insisted that these events should be viewed as "celebrations" and spontaneous gatherings, and not as protests or organized demonstrations.[5][6] This stance allows Critical Mass to argue a legal position that its events can occur without advance notification of local police.[7][8]

    Contents

    History

    Critical Mass-like bike tours with hundreds of participants took place in Stockholm, Sweden in the early 1970s.[9] But the first ride within the present wave took place on Friday, September 25, 1992 at 6 pm in San Francisco. At that time, the event was known as Commute Clot and was composed of a couple of dozen cyclists who had received flyers on Market Street.[2]

    Shortly after this, some participants in that ride went to a local bicycle shop for a screening of Ted White's documentary Return of the Scorcher, about bike culture overseas. In that film, American human powered vehicle and pedicabs designer George Bliss noted that, in China, both motorists and bicyclists had an understood method of negotiating intersections without signals. Traffic would "bunch up" at these intersections until the backlog reached a "critical mass", at which point that mass would move through the intersection. That term from the movie was applied to the ride,[10] and the name caught on, replacing "Commute Clot" by the time of the second event.[2]

    By the time of the fourth ride, the number of cyclists had increased to around 100 and participation continued to grow dramatically, reaching about 1,000 riders, on average.[2]

    The name was soon adopted as a generic label by participants in similar but independent mass rides that were either initiated in various locations around the world at around the same time, or had already existed before 1992 under other names. It is estimated that there are Critical Mass-type rides in more than 325 cities to date. The term "masser" is sometimes applied to a frequent participant.[11]

    Organization and tactics

    Structure

    Critical Mass has a decentralized (rather than hierarchical) structure. Critical Mass is sometimes called an "organized coincidence", with no leadership or membership. The routes of some rides are decided spontaneously by whoever is currently at the front of the ride, while others are decided prior to the ride by a popular vote of suggested routes often drawn up on photocopied fliers. The term xerocracy was coined to describe a process by which the route for a Critical Mass can be decided: anyone who has an opinion makes their own map and distributes it to the cyclists participating in the Mass. Still other rides decide the route by consensus. The disorganized nature of the event allows it to largely escape clampdown by authorities who may view the rides as forms of parades or organized protest. Additionally, the movement is free from the structural costs associated with a centralized, hierarchical organization. In order for the event to function, the only requirement is a sufficient turn-out to create a "critical mass" of riders dense enough to occupy a piece of road to the exclusion of drivers of motorized vehicles. Authorities in New York, California and Oregon have expressed concern with the difficulty of coordinating with the riders, due to the lack of leadership.[12][13][14]

    Scale

    Bike lift in Budapest, September 22, 2007

    Critical Mass rides vary greatly in many respects, including frequency and number of participants. For example, many small cities have monthly Critical Mass rides with fewer than twenty riders which offer safety in numbers[15] to cyclists in those locales, while on the opposite extreme, in what have been the largest events using the name Critical Mass, cyclists in Budapest, Hungary hold only two rides each year on April 22 (Earth Day) and September 22 (International Car Free Day). The "Budapest style" attracts tens of thousands of riders.[16] The April 20, 2008 Budapest ride participation was estimated at 80,000 riders.[17][18]

    Corking

    Detail from the November 20, 1992 flyer by Joel Pomerantz which introduced the concept of corking

    Because Critical Mass takes place without an official route or sanction, participants in some cities have sometimes practiced a tactic known as "corking" in order to maintain the cohesion of the group. This tactic consists of a few riders blocking traffic from side roads so that the mass can freely proceed through red lights without interruption. Corking allows the mass to engage in a variety of activities, such as forming a cyclone, lifting their bikes in a tradition known as a "Bike Lift" (in Chicago this is referred to as a Chicago hold-up), or to perform a "die-in" where riders lie on the ground with their bikes to symbolise cyclist deaths and injuries caused by automobiles, very popular in Montreal. The "Corks" sometimes take advantage of their time corking to distribute fliers.

    The practice of corking roads in order to pass through red lights as a group is in contravention of traffic laws that govern cyclist traffic and is contrary to Critical Mass' claim that "we are traffic", since ordinary traffic (including bicycle traffic) does not have the right to go through intersections once the traffic signal has changed to red[19]. Corking has sometimes led to hostility between motorists and riders, even erupting into violence and arrests of motorists and cyclists alike during Critical Mass rides.[20]

    Other bicycling groups

    Similar organizations and movements

    The Critical Mass rides have inspired a number of other bicycle movements, that range from political movements to the "Critical Tits" ride during the yearly Burning Man festival.[21] In Chicago, a movement has grown out of the Critical Mass community to promote winter cycling via the bikewinter campaign.[22] The extensive news coverage of San Francisco's July 1997 ride spawned an international celebration of bicycling, called Bike Summer.[23] Kidical Mass originated in Oregon, and encourages bicycle riding for children and families.[24] Critical Sass is an all female version of the ride in Baton Rouge, Louisiana, that takes place the second Friday of every month. Tweed run is a well dressed mass which takes place annually in a number of cities across the world. Examples of Critical Mass rides for political movements includes the Free Tibet Rides (May 2008): Free Tibet Critical Mass in Columbia, Missouri, "Tibetan Freedom Bike Rally" in San Francisco (Aug 2008), and in "Bike Ride for Tibet" in London (Aug 2008).[25]

    San Jose is the home to the San Jose Bike Party. Bike Party rides on the third Friday of the month with a different starting point and route each time. Rides are typically 20 – 25 miles in length and usually have 2,500 - 3,500 riders, with a peak of 4,300 in October 2009. The ride aims to build a community of cyclists and prove that bikes can co-exist with cars. It is different than Critical Mass in that it rides after rush hour and obeys all traffic laws and has a pre-determined route.[26]

    In Portland Oregon a tactic called a “bike swarm” has been used by Occupy Wall Street protesters to separate marching protesters from police. [27] [28]

    Critical Manners

    Critical Mass riders pass the World of Coke in Atlanta

    In San Francisco, an event known as "Critical Manners" was created as a response to Critical Mass. Critical Manners rides through the city on the second Friday of the month, with riders encouraged to obey all traffic laws such as stopping at red lights and signaling.[29][30] Tucson, Arizona holds the Tuesday Night Community Bike Ride as their alternative to Critical Mass. The weekly ride encourages bicycle commuting and motor vehicle awareness in a peaceful and friendly way.[31]

    In 2007 there were conversations about starting Critical Manners in Portland, Oregon.[32] According to the Critical Mass book, a similar project known as Courteous Mass is described as "an alternative to Critical Mass."

    An alternative ride named RideCivil formed in Seattle in late 2007.[33] Rides are on the second Friday of every month, and focus on encouraging civility between motorists, pedestrians and cyclists.[34]

    On June 12, 2009, an Indianapolis Critical Manners ride was launched[35] and remains active.[36]

    On August 14, 2009 there was a Critical Manners ride in Vancouver, British Columbia.[37] The ride consisted of between 70-100 cyclists riding through the downtown core, making all attempts to follow the rules of the road (stopping at red lights / stop signs, using hand signals to turn, using the right-most lane or bike lane when applicable). The event generated some coverage in the local media[38] and was generally deemed a success by the participants, although there were some criticisms.[39] The ride only survived one outing.[40]

    Conflicts involving Critical Mass

    Critical Mass rides have generated controversy and public opposition.[41] Some critics claim that Critical Mass is a deliberate attempt to obstruct traffic and disrupt normal city functions, asserting that individuals taking part refuse to obey traffic laws.[42] Altercations with police and motorists have occurred. Although uncommon, protesters are sometimes present at Critical Mass events to oppose the group's methods.

    Some bicycling advocacy groups have expressed concern that the "subversive" nature of Critical Mass and altercations with motorists could weaken public support for bicyclists.[13] Though it does not condone incidents of violence and rudeness, the San Francisco Bicycle Coalition credits Critical Mass with spotlighting bicycle issues and aiding their efforts in advocating for cyclists.[2]

    See also

    References

    1. ^ Richard Madden (December 15, 2003). London: How cyclists around the world put a spoke in the motorist's wheel. The Daily Telegraph. http://www.telegraph.co.uk/travel/729324/London-How-cyclists-around-the-world-put-a-spoke-in-the-motorist%27s-wheel.html 
    2. ^ a b c d e Garofoli, Joe (September 28, 2002). "Critical Mass turns 10". San Francisco Chronicle. http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2002/09/26/BA133774.DTL. Retrieved July 2, 2007. 
    3. ^ Mcgrath, Ben (November 13, 2006). "Holy Rollers". http://www.newyorker.com/printables/fact/061113fa_fact. 
    4. ^ "Critical Mass London". Urban75. 2006. http://www.urban75.org/photos/critical. 
    5. ^ "Pittsburgh Critical Mass". http://pghcriticalmass.org/. Retrieved November 16, 2009. 
    6. ^ "Critical Mass: Over 260 Arrested in First Major Protest of RNC". Democracy Now!. August 30, 2004. http://www.democracynow.org/article.pl?sid=04/08/30/1453256. 
    7. ^ Seaton, Matt (October 26, 2005). "Critical crackdown". London: The Guardian. http://www.guardian.co.uk/g2/story/0,3604,1600570,00.html. 
    8. ^ Rosi-Kessel, Adam (August 24, 2004). "[*BCM* Hong Kong Critical Mass News"]. http://www.bostoncriticalmass.org/pipermail/bostoncriticalmass/2004-August/000146.html. 
    9. ^ "Cyklister i Storstockholm" (in Norwegian). http://www.alternativstad.nu/Dokument/cyklister-i-storsthlm.html. Retrieved November 16, 2009. 
    10. ^ Pomerantz, Joel (2002). "A Critical Mass Cultural Glossary". In Carlsson, Chris. Critical Mass: Bicycling's Defiant Celebration. Edinburgh, Scotland: AK Press. ISSN 1-902593-59-6. http://www.joelpomerantz.com/genlresources/cmglossary.html 
    11. ^ "About Critical Mass". Chicago Critical Mass. http://chicagocriticalmass.org/about/faq. Retrieved November 16, 2009. 
    12. ^ Susan Palmer (May 20, 2006). "Rolling protests hit bump". The Register-Guard (Eugene, OR). http://www.registerguard.com/news/2006/05/20/a1.criticalmass.0520.p2.php?section=cityregion. 
    13. ^ a b Martha T. Moore (November 15, 2004). "Big pack of bikes piques police". USA Today. http://www.usatoday.com/news/nation/2004-11-15-bikes-new-york_x.htm. 
    14. ^ Dylan Bennett and Gretchen Giles. "Bicyclists see transportation as critical". MetroActive News & Issues. http://www.metroactive.com/papers/sonoma/04.03.97/bikes-9714.html. Retrieved November 16, 2009. 
    15. ^ Gaffney, Dan (September 3, 2008). "A virtuous cycle: safety in numbers for riders says research". http://www.science.unsw.edu.au/news/a-virtuous-cycle-safety-in-numbers-for-riders-says-research. Retrieved October 3, 2008. 
    16. ^ "A critical mass critique". Budapest Sun Online. April 20, 2008. http://www.budapestsun.com/news/48369. Retrieved November 16, 2009. 
    17. ^ "Minden eddiginél többen vettek részt a Critical Mass felvonuláson" (in Hungarian). MTI. http://mti.hu/cikk/266730/. Retrieved November 16, 2009. 
    18. ^ "Critical Mass wheels away". Budapest Sun Online. April 23, 2008. http://www.budapestsun.com/news/60058. Retrieved November 16, 2009. 
    19. ^ "Motor Vehicle Act, R.S.B.C. 1996 c.318 ss.119, 183 - Definitions, Cycle; Rights and Duties of Operator of Cycle". Revised Statutes of British Columbia. CanLii. http://www.canlii.org/eliisa/highlight.do?text=%22rights+and+duties+of%22&language=en&searchTitle=British+Columbia&path=/en/bc/laws/stat/rsbc-1996-c-318/89130/part-6/rsbc-1996-c-318-part-6.html. Retrieved 3 August 2011. 
    20. ^ Gutierrez, Scott (July 3, 2006). "2 bicyclists arrested at Critical Mass get out of jail". Seattle Post-Intelligencer. http://seattlepi.com/local/276237_sheriff03.html. 
    21. ^ "Critical Tits Party FAQ". http://www.criticaltits.com/faq.html. Retrieved February 22, 2008. 
    22. ^ "Chicago Bikewinter". http://www.bikewinter.org. Retrieved November 16, 2009. 
    23. ^ "BikeSummer 2006: History". http://www.bikesummer.org/2006/history/history.php. [dead link]
    24. ^ "Kidical Mass". http://www.kidicalmass.org/. Retrieved November 16, 2009. 
    25. ^ "Free Tibet protesters hit the streets on bikes". http://www.columbiamissourian.com/stories/2008/05/02/free-tibet-protesters-hit-streets-bikes/. Retrieved November 26, 2008. 
    26. ^ "San Jose Bike Party - How We Ride!". http://www.sjbikeparty.org/how-we-ride. Retrieved November 16, 2009. 
    27. ^ Jonathan Maus “The ‘bike swarm’ evolves into a movement of its own”, Bike Portland, 23 November 2011
    28. ^ [“Riot police use petter spray to try to control Occupy crowd”, KATU, 17 November 2011]
    29. ^ Steve, Rubenstein (April 14, 2007). "Critical Manners takes a stand for sharing, harmony, red lights.". San Francisco Chronicle. http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2007/04/14/MNGB6P8R1U1.DTL. Retrieved July 2, 2007. 
    30. ^ Steve Rubenstein (April 13, 2007). "Critical Manners ride starts at 6 pm". The San Francisco Chronicle. http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2007/04/13/BABADIGEST4.DTL. Retrieved February 23, 2008. 
    31. ^ Herreras, Mari (November 8, 2007). "Tucson on Two Wheels". Tucson Weekly. http://www.tucsonweekly.com/gbase/Currents/Content?oid=102923. Retrieved December 10, 2008. 
    32. ^ Jonathan Maus (August 14, 2007). "Would Critical Manners Catch On In Portland?". http://bikeportland.org/2007/08/14/would-critical-manners-catch-on-in-portland/. Retrieved November 16, 2009. 
    33. ^ "Critical Man-nerds ride report". Bike Hugger. October 16, 2007. http://bikehugger.com/2007/10/critical_mannerds_ride_report.htm. Retrieved February 25, 2009. 
    34. ^ "Seattle Ride Civil website". http://seattle.ridecivil.org. Retrieved November 16, 2009. [dead link]
    35. ^ "Courteous Mass, Critical Manners". INDYCOG. June 3, 2009. http://www.theindycog.com/labels/Critical%20Manners.html. Retrieved November 1, 2010. 
    36. ^ "Indianapolis Courteous Mass, Critical Manners Facebook page". Facebook. http://www.facebook.com/group.php?gid=111752148046&ref=ts. Retrieved November 1, 2010. 
    37. ^ "The Long-Awaited Route". WordPress.com. August 12, 2009. http://criticalmanners.wordpress.com/2009/08/12/the-long-awaited-route/. Retrieved November 16, 2009. 
    38. ^ David Carrit (August 1, 2009). "Cyclists launch well-mannered rival to Critical Mass". The Province. http://www.theprovince.com/travel/Cyclists+launch+rival+Critical+Mass/1850693/story.html. Retrieved November 16, 2009. [dead link]
    39. ^ "We did it!". Wordpress. August 14, 2009. http://criticalmanners.wordpress.com/2009/08/14/we-did-it/#comments. Retrieved November 16, 2009. 
    40. ^ "Ride postponed". Wordpress. September 9, 2009. http://criticalmanners.wordpress.com/2009/09/09/ride-postponed/. Retrieved November 16, 2009. 
    41. ^ Michael Cabanatuan, Jaxon Van Derbeken and Cecilia M. Vega (April 5, 2007). "Clash reignites road wars:Skirmish between driver, Critical Mass participants triggers another round of debate about monthly ride". San Francisco Chronicle. http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2007/04/05/CRITICAL.TMP. 
    42. ^ Gord MacFarlane (August 7, 2006). "Critical Mass protesters too critical". Winnipeg Sun. http://winnipegsun.com/News/Columnists/MacFarlane_Gord/2006/08/06/1722420.html. 

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