Difference between revisions 3698885 and 3698911 on simplewiki

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'''Spacetime''' is a model in [[physics]] that joins the three [[dimension]]al space and one dimensional [[time]] into the idea of [[space-time continuum]]. Combining these two ideas helped [[physicist]]s to make many laws of physics easier to understand, and to explain how the universe works on the big level (e.g., [[star]]s) and small level (e.g., [[atom]]s).

The actual number of [[dimension]]s in spacetime is not fixed, but usually spacetime means a four dimensional (three dimensions of space and one dimension of time) spacetime. Some other theories claim that there are more than four dimensions.

== Historical origin ==
Many people link spacetime with [[Albert Einstein]] who found [[special relativity]]. However, it was Einstein's teacher, [[Hermann Minkowski]], who suggested this idea. He hoped this new idea would clarify the theory of special relativity.

== Spacetime in general relativity ==
In [[general relativity]], spacetime is curved by the existence of [[matter]], [[energy]], and [[momentum]], as said by the [[Einstein field equations]].

Many continuous space-time leads to strange physical understanding. For this reason, many mathematical physicists (physicists who use math to physical questions) study only seemingly real set of spacetime.

== Spacetime in quantum mechanics and disagreements ==
In [[general relativity]], spacetime is thought as smooth and continuous. However in the theory of [[quantum mechanics]], spacetime is not always continuous.

[[Category:Basic physics ideas]]
[[Category:Relativity]]
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[[zh:时空]][[User:Twhitguy14|Twhitguy14]] ([[User talk:Twhitguy14|talk]]) 15:00, 29 June 2012 (UTC)<gallery>
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''An illustration of the space-time curvature caused by Earth''


'''Spacetime''' is any scientific model that merges the three-dimensions of [[space]] and one dimension of [[time]] into a single construct. The concept of spacetime was introduced by [[Albert Einstein]]
in his [[General Theory of Relativity]]. It is accepted as the cause of [[gravity]].

== Spacetime Curvature and Gravity ==

===== The Curvature of Spacetime =====
Spacetime can be thought of as a flexible rubber sheet that can be bent, or ''warped''. When heavy objects (like the [[Sun]], the [[Earth]], or other heavenly bodies) are put on spacetime, they cause a curve in the smooth sheet of spacetime. 

===== Gravity as Curved Spacetime =====
When spacetime is curved, it causes a pull on the sheet, and therefore causes smaller objects to be drawn near it. Take, for example, an ant on a rubber sheet. If the sheet is smooth, the ant walks in a straight line. But if a bowling ball is dropped beside the ant, the sheet will be warped, and the ant's naturally straight path will be distorted to orbit around the bowling ball. This is the explanation of gravity presented by Einstein. 

== Spacetime and Quantum Theory ==
When we try to combine spacetime with [[Quantum Mechanics]], we find some ''big'' disagreements. Mainly, spacetime makes everything as if it were a smooth, continuous flow; Quantum Theory says that everything is discrete and tiny, like packets. (Atoms, photons, etc.)