Why is it that the battery in the smoke detector always loses its power in the middle of the night?

I find waking up in the wee, dark hours to an incessant CHIRP [pause] CHIRP [pause] to be annoying and not conducive to a restful sleep.

The smoke detector is not far from my bedroom door. The [pause] is just long enough to begin to drift back to sleep… then the next CHIRP sounds. And I lay in bed, trying to ignore the CHIRP, but knowing that the only way to fix the problem is to change the #$@% battery.

CHIRP

Mom crawls out of bed with eyes only half open. Is it really the smoke detector, or maybe something easier to deal with?

CHIRP

It’s really the smoke detector. Do we even have a battery? There’s got to be one here in the kitchen junk drawer. I need a 9-volt…

CHIRP

OK. Battery in hand. Now I need the step ladder.

CHIRP

C’mon detector… come off the ceiling! oh yeah… gotta unplug this doohickey. Open the little door. Old battery out. New battery in. New battery in. New battery in. It came out, it must go back… go back! there.

Now… can I hook the little plug doohikey back up… can I get my bifocals in the right position so I can see the little plug doohickey and where it needs to go while precariously perched on the top of a tippy step ladder? If I could only lean just a little further back…. whew…

attach the thing back to the ceiling, and to bed… c’mon detector, attach already… please… PLEASE!

Now, test. Nothing. [sigh] pull from ceiling, check connections, test

CHIRP CHIRP CHIRP

good enough. attach to ceiling… attach to ceiling… why is this so hard? attach to ceiling…

silence

bed… sleep…

Why is it always in the middle of the night?