## Encyclopedia > Talk:Space-time

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# Talk:Spacetime

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Summaries of earlier Talk (see [1] (http://www.wikipedia.com/wiki.cgi?action=history&id=Space-time/Talk))

### Space-time vs. Spacetime

Examples of use of spacetime:
• Weisstein's encyclopedia http://www.treasure-troves.com/physics/
• D. J. Griffiths' Introduction to Electrodynamics (Upper Saddle River, N. J.: Prentice-Hall, 1989)
• numerous books with spacetime in title
• E. F. Taylor and J. A. Wheeler, Spacetime Physics (San Francisco: W. H. Freeman, 1966)
• Caltech class: "Spacetime 101"
• .edu matches online are almost exclusively for spacetime

Examples of use of space-time:

• Brehm & Mullin, Introduction to the Structure of Matter (ISBN: 047160531X)
• Merriam-Webster http://www.m-w.com
• space-time about four times as many hits as spacetime on AltaVista

### The Spacetime four vector

The space-time four vector is:

[x y z ct]

the use of the vector as:

[x y z ict]

was common about 40 years ago or so, but it is now considered archaic and the former notation is prefered.--BlackGriffen

However, there are certainly physicists who prefer the i notation, including [http://www.stardrive.org|Dr. Jack Sarfatti].

The Wikipedia should present the mainstream state of a field as much as possible, presenting relevant dissenting views as such when they arise. The use of the i is just a lazy way to make finding the "length" squared of a four vector feel like finding the length of any other vector (dot product the vector on to itself). It is, however, just as easy to define a new "length" operator for four vectors that doesn't require complex numbers.

And if bandying about names is the game, a quick look at the Feynmann Lectures on Physics explanation of four vectors shows nary an i, even though he had a discussion of using c=1.--BlackGriffen

I concur: both 'space-time' and the 'i' notation appear to be common early usage, and physicists everywhere seem now to have standardised on both 'spacetime' and the 'i'-less notation -- The Anome

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