Re: Why are there weird creaking noises at night in your house?

Hi Ashley!

You've asked a very good question, and it shows that you are both 
observant and inquisitive, which are two great qualities to have.  

To answer your question, your house creaks because it is haunted.  
Just kidding.

Your house creaks at night because the wood frame is shifting and 
contracting as it cools off.  During the day, the sun and the weather 
heats up your house, which makes the wood in the frame and walls expand a 
little.  At night, when it cools off, the wood shrinks back down to the 
normal size, and when it does that, sometimes two surfaces rub against 
each other and it creaks or groans.  It's the same kind of creaks you get 
when a wooden door rubs on the door jamb.  (Which is different from the 
squeaky hinge sound...)  The "creakiness" of your house will vary 
according to how hot the day was, how cold the night is, humidity, time of 
year, and a bunch of other factors.

I'd hazard a guess that your house is at least ten years old, and it's 
primarily made of wood.  The wood part is a pretty easy guess.  Most 
houses in California are made out of wood, because wood does better than 
brick during earthquakes.  For 
comparison, most houses in the midwest (where the big natural disaster is 
tornadoes) are made 
from brick, and most houses in the northeast (where blizzards are more common) are made of 
stone.  (I'd like to go on record as saying that the "Three Little Pigs" 
story annoyed me a little growing up.  The pigs built a brick house after 
the wooden one fell down, but wooden houses are more structurally stable 
in California...  What's up with that?)

I hope this helps with your experiment.  Let us know what you're doing and 
how it turns out.  And keep asking questions!

Jeff Yap
Mad Scientist