A Civil Dawn

We headed out the door at 4:29 am to catch our flight to the West Coast. After less than 3 hours sleep I crawled out of bed at 3:45 am. As we headed to the airport, Barnacle Boy and Crash Kid were bantering excitedly, as well complaining good naturedly about having to arise before dawn. Math Man wondered, if out of compassion for the parents, they might be a bit more civil. I said I thought civil dawn was later than this.

All this led to a conversation about the different ways to define dawn. My phone reports the time of astronomical dawn, nautical dawn and civil dawn. (Today that would be 3:49 am, 4:34 am and 5:14 am, respectively!). Crash wanted to know how the dawns were determined - and other than astronomical dawn, I only had some vague idea the decision hinged on whether or not you could read text outside.

Should you care - astronomical dawn is when the sun is 18^o below the horizon and the sky begins to lighten enough to obscure astronomical features. Nautical dawn is when the sun is 12^o below the horizon, but objects can be distinguished. Civil dawn is when the sun is 6^o below the horizon and the ground is visible enough to begin outdoor activities. And of course, none of these times should be confused with sunrise!

I propose we redefine civil dawn as the hour in the day when you can be civil to (a) strangers and (b) siblings. Experience tells me that (a) would be significantly earlier than (b).