It lasts until the sigil is interrupted, unless installed with a timer.
[With a finger he smudges the chalk on one of the sigils, and its light dies.]
Chalk, for obvious reasons, isn't practical for long-term sigils. As for the theory, I once heard Professor Grouse hypothesise that the language of magic captures the magical energy of the dimension directly ... I believe he used the phrase 'quantum harmonic oscillator'?
[His brow furrows.]
That was some time ago, however. I don't know whether he's confirmed that hypothesis or not. Regardless, the shape, depth and size of a sigil defines how that energy is used.
no subject
[With a finger he smudges the chalk on one of the sigils, and its light dies.]
Chalk, for obvious reasons, isn't practical for long-term sigils. As for the theory, I once heard Professor Grouse hypothesise that the language of magic captures the magical energy of the dimension directly ... I believe he used the phrase 'quantum harmonic oscillator'?
[His brow furrows.]
That was some time ago, however. I don't know whether he's confirmed that hypothesis or not. Regardless, the shape, depth and size of a sigil defines how that energy is used.