Walk This Way: I wonder (as I wander)...

It makes you think ... No, I mean it REALLY makes you think. You can't help it. Even when walking with friends, there are times when, either because our various paces fall out of synch, or one needs a fuel or water break or to catch a breath, or simply when the peace and quiet overtakes you and you walk alongside each other in silence, you find yourself wondering about all sorts of things. At first I thought it was just me but as time has gone on I've realised that many a conversation starts up with "I was thinking ..." or often, in my case certainly, "I wonder..."

Thanks to the joys of the Internet (which has become lovingly renamed The Wiffy)

[wifi] I've been able to satisfy many of those idle curiosities when the day's walking is over. Today I was wondering why there are so many eucalyptus trees in Galicia. I thought it was native to the antipodes. These huge trees line much of the footpath, soaring skyward straight as a die, their bark-stripped trunks pale and smooth and their grey-green leaves only starting many feet above our heads. It seems they were imported years ago and actively promoted by the paper industry in the 20thC. Now, magnificent as they are, I've learned that the forests are less easy to contain and, lacking much formal management, pose a serious fire risk. So now you know.

Ok, I've told you something you maybe didn't know before. So, in the spirit of tit for tat, can anyone answer me this? I've looked it up on The Wiffy but I'm still mystified.

Why does our dirty washing take up more space than the clean did in our suitcase???