> # Re: off topic

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> Posted by Sarah Tonin on January 18, 2016 at 16:02:33

> In Reply to: Re: off topic posted by veronica norderney on January 15, 2016 at 17:15:55:

> Because cross products only work in three dimensions (x,y,z), and spacetime needs four dimensions (t,x,y,z)...

> More precisely, a cross product has three components (x=yz-zy, y=zx-xz, z=xy-yx) ... mnemonic XYZZY ... but when you add the time dimension it combines with each of the existing three, giving six. You can't fit six components into a four-dimensional vector, so you have to fit them into a four-by-four matrix (tensor), each one twice, leaving the leading diagonal zeroised.

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> If light can't escape from a black hole, how come gravity can?

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> - Re: off topic Adelsha Ronden 21:10:52 1/18/2016 (0)

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