Arthritis & Rheumatism

What makes joints pop and crack and is it a sign of disease?

Joints emit a variety of noises, including popping, snapping, catching, clicking, grinding, grating and clunking. The technical term for these noises is "crepitus", from the Latin "to rattle". People of all ages can experience ...

Autism spectrum disorders

People with autism have an altered sense of self

New research has indicated that people with autism have an altered sense of self, which may explain some of the differences shown in social functioning.

Psychology & Psychiatry

Lonely people stand farther from loved ones, study finds

A new study from the University of Chicago found that people who report feeling lonely also say they sit or stand physically farther away from close friends and family. Their "personal space" for intimate partners is larger ...

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Space

Space is the boundless, three-dimensional extent in which objects and events occur and have relative position and direction. Physical space is often conceived in three linear dimensions, although modern physicists usually consider it, with time, to be part of the boundless four-dimensional continuum known as spacetime. In mathematics spaces with different numbers of dimensions and with different underlying structures can be examined. The concept of space is considered to be of fundamental importance to an understanding of the universe although disagreement continues between philosophers over whether it is itself an entity, a relationship between entities, or part of a conceptual framework.

Many of the philosophical questions arose in the 17th century, during the early development of classical mechanics. In Isaac Newton's view, space was absolute - in the sense that it existed permanently and independently of whether there were any matter in the space. Other natural philosophers, notably Gottfried Leibniz, thought instead that space was a collection of relations between objects, given by their distance and direction from one another. In the 18th century, Immanuel Kant described space and time as elements of a systematic framework which humans use to structure their experience.

In the 19th and 20th centuries mathematicians began to examine non-Euclidean geometries, in which space can be said to be curved, rather than flat. According to Albert Einstein's theory of general relativity, space around gravitational fields deviates from Euclidean space. Experimental tests of general relativity have confirmed that non-Euclidean space provides a better model for explaining the existing laws of mechanics and optics.

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