Wikispaces is a wiki hosting service based in San Francisco that was launched in 2005. It hosts private wikis for businesses, non-profits, and educators for an annual fee. As of 2009, Wikispaces had over 2.2 million registered members and hosted more than 900,000 wikis. It has also provided over 100,000 free wikis to K-12 educators.

5. Wikispaces is a hosting service (sometimes called a wiki farm) based in San Francisco, California. Launched in March 2005, Wikispaces is owned by Tangient LLC and is among the largest wiki hosts, competing with PBworks, Wetpaint, Wikia, and Google Sites (formerly JotSpot).[1] Private wikis with advanced features for businesses, non-profits and educators are available for an annual fee. As of March 2008, they had more than 920,000 registered members and hosted more than 390,000 wikis.[2] By March 2009, that number had increased to over 2.2 million registered members and more than 900,000 wikis.[3] Wikispaces has also given away more than 100,000 premium wikis to K-12 educators.[4] Since 2010 Wikispaces have cooperated with web 2.0 education platform Glogster EDU. Glogster EDU embeds Glogs into Wikispaces services.

9. In physics, spacetime (or space–time; or space/time) is any mathematical model that combines space and time into a single continuum. Spacetime is usually interpreted with space being three-dimensional and time playing the role of a fourth dimension that is of a different sort from the spatial dimensions. According to certain Euclidean space perceptions, the universe has three dimensions of space and one dimension of time. By combining space and time into a single manifold, physicists have significantly simplified a large number of physical theories, as well as described in a more uniform way the workings of the universe at both the supergalactic and subatomic levels. In classical mechanics, the use of Euclidean space instead of spacetime is appropriate, as time is treated as universal and constant, being independent of the state of motion of an observer. In relativistic contexts, however, time cannot be separated from the three dimensions of space, because the observed rate at which time passes for an object depends on the object's velocity relative to the observer and also on the strength of intense gravitational fields, which can slow the passage of time.( www.wikipedia.com)