We recently build a new house. During the night really loud popping noises start coming from the attic, so loud that they awake me, it can to me be quite frightening. Is it the timber expanding and contracting that makes up the roof?

It very well could be your house is settaling. How long ago was the home built? Do you have a full basement? What kind of walls are in the basement? (wood,concrete,block) Is your house a single story or two story? And last of all where are you located? The climate you live in could have a lot to do with it. Cracking and popping noises are common (to a point) in new homes.
Mike

I'd say it is still settling, quite common in new houses

Both guys can be correct but most noise in a brand new house comes from the lumber drying out which happens long before settling gets going. Have you noticed and drywall nail pops that weren't there when you moved in? Studs, rafters, joist all shrink when they dry and most construction gets pretty wet until the house is buttoned up and weather tight.