How many dimensions are required minimum for an object to block light?

in 1d I doubt it's possible.

in 2d I think it could do it if only the light was limited to a dimension perpendicular to the 'thickness' dimension

in 3d I think it could do it no matter what dimension the object was looked at in.

Clarification: 3d -> A block of wood can "block light" (make a shadow) no matter how you shine light at it.

Edit: What about what are the minimum dimensions needed to block light assuming you are dealing with an $n$ dimensional space?

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    $\begingroup$ As Jim said in his answer, I don't think it's clear what you're asking. Could you clarify? $\endgroup$
    – David Z
    Aug 18, 2012 at 2:53
  • $\begingroup$ Also depends on how many dimensions you're considering in the first place. In 1D, a 1D object would successfully "block" light, same goes for a 2D/3D object in their respective number of dimensions. $\endgroup$
    – Kitchi
    Nov 25, 2012 at 18:38
  • $\begingroup$ Ohhhh haha interesting :). So how about the minimum number of dimensions needed to block light from $n$ dimensions? $\endgroup$ Nov 26, 2012 at 3:46

2 Answers 2


I m not sure I understand your question, but a quasi one dimensional object like a needle can absorb light or electromagnetic waves polarized in the right direction, and a parallel "forest" of needles will block "light" or waves of that polarization, but pass waves of the perpendicular polarization. I hope this partially answers your question.


How about zero dimensions? A non-rotating black hole singularity is zero dimensional, It surly blocks light... :)

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    $\begingroup$ The "black hole singularity" is not what is blocking the light. It is also not appropriate to view the singularity as the black hole source. $\endgroup$
    – Ron Maimon
    Aug 27, 2012 at 9:03
  • $\begingroup$ blocking is trapping in this case... it is the same thing. A ray of light that its k-vector is pointing at the vicinity of the black hole singularity will get trapped in it. forever... $\endgroup$
    – bla
    Aug 27, 2012 at 14:52
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    $\begingroup$ I am pretty tired of repeating this: nobody knows for sure if things are trapped in black holes, I believe that for spinning and charged black holes, it just comes out later. For light, we know it just goes in and comes out from D-brane calculations by Gubser in the 1990s. Regarding the singularity, it isn't a "thing"--- the horizon is the "thing". $\endgroup$
    – Ron Maimon
    Aug 27, 2012 at 21:05

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