Nothing wakes our baby up

I was looking for my shirt in a very dark room for about 5 minutes before I realised that I could just turn the light on. A second later, I remembered why the light was off in the first place. There was a baby asleep in the room. This proved that a) I'm so tired my brain doesn't work, b) a bright light shining directly in his face doesn't bother our baby at all. Now I'm intrigued. Time to find out what else doesn't wake him up.