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I was scrolling through a wiki article on terminal velocity when I spotted an upside down delta. What does this symbol mean? How is it applied in other contexts?

EDIT: If possible could someone expand upon "a covariant vector made of space derivatives?" I sort of understand how a vector can be made up of partial derivatives, but what does covariant mean?

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    $\begingroup$ Does this answer your question? $\nabla$, $\cdot \nabla$, $\nabla \cdot$, $\nabla^2$ - What do they do? $\endgroup$
    – Amit
    Jun 3, 2023 at 17:34
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    $\begingroup$ Yes @Amit this looks like it answers my question thoroughly! $\endgroup$
    – Carlo
    Jun 3, 2023 at 17:57
  • $\begingroup$ Re: Edit -- This question is now closed as a duplicate, and in general posts should contain one question without being later edited to widen their scope. You may of course post a new question -- but I strongly suggest that you first carry out a search to see if a similar question to your new one also exists. For more general guidance on how to ask a good question click here $\endgroup$
    – Amit
    Jun 3, 2023 at 18:19

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That is the Nabla, and it just means the covariant vector made of space derivatives.

Edit: $$\vec\nabla f= \begin{pmatrix} \dfrac{\partial f}{\partial x}\\ \dfrac{\partial f}{\partial y}\\ \dfrac{\partial f}{\partial z} \end {pmatrix}$$

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  • $\begingroup$ What is a covariant vector? Or space derivatives? But thank you for answering my question despite my ignorance. $\endgroup$
    – Carlo
    Jun 3, 2023 at 17:16
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    $\begingroup$ Check the new edit. I think you are far from understanding what is needed to explain covariant, but space derivatives should be understandable. $\endgroup$ Jun 3, 2023 at 17:24
  • $\begingroup$ Oh I see a vector made of partial derivatives using Cartesian coordinates. I'd assume this vector can take many forms, 1x3, 2x3, 3x3... or does that exclude it from being "covariant." Also your right, I probably will not be able to understand covariance. $\endgroup$
    – Carlo
    Jun 3, 2023 at 17:56
  • $\begingroup$ @Carlo Have you seen vectors that are 2x3, 3x3, etc.? $\endgroup$
    – Ghoster
    Jun 4, 2023 at 4:32
  • $\begingroup$ @Ghoster I’m kind of a goof I got mixed up between matrices and vectors. I’ve learned a tiny bit more about grad and its a function that converts scalars into vector fields. $\endgroup$
    – Carlo
    Jun 4, 2023 at 14:35

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