[RPG] cast the Light cantrip on an 11-foot pole


The description of the Light spell in D&D 5e says:

You touch one object that is no larger than 10 feet in any dimension. Until the spell ends, the object sheds bright light in a 20-foot radius and dim light for an additional 20 feet. (…)

Can I cast the Light cantrip on an 11-foot pole?

On one hand, 11 is greater than 10. This would suggest that the answer to my question is "no".

On the other hand, I could put an 11-foot pole in a 10×10×10-foot box. This would suggest that the answer is "yes".

I don't expect that the success of an adventure will hinge on the answer to this question any time soon, but I would like to understand how dimensions are supposed to work.

Best Answer

No, you can't cast light on it.

If the spell intended to say "an object that fits within a 10-foot cube", it would say that, or something like it. The phrase "no larger than 10 feet in any dimension" is very clear: the object can't be more than 10 feet in its longest possible measure. You don't get to pick an arbitrary X-, Y-, and Z-axis and only measure against those three.

This does leave a hole in the rules where you cast light on an object that is less than 10 feet long, and then change it so that it is longer - for example, casting it on a ball of yarn that you then unroll, or a telescoping pole that you then extend. I would probably rule that when the object expands past 10 feet, it becomes an invalid target and the spell fizzles out, but that's just my ruling.