The Doctor/ Sirius Black
"Erm, no. It's a universe thing. Science. The sun- suns? Well, whatever sun you have emits it all the time. S'why it burns some people's skin. You emit it- just a little bit, at least. S'normal. If there's too much though, it can be very bad." She could draw a diagram to explain but figured that Sirius was probably not as interested in that given his expression.
At least she'd caught on what a muggle was, though! She was making progress.
"Yea, I don't anyone else saw it comin'." She smirked, pocketing her sonic in her jacket pocket and sipping her drink.
"Anyway, we're safe here. For the most part. Now...tell me about your and- how's it work? Think I could borrow it at some point??"