Do you have blinds behind your curtains? Or a fence outside, between your window and the morning sun?

Parallel lines of light and shadow must be caused by some linear feature in your environment, between your window and the rising sun. Look around for anything like blinds, a fence, or even long eucalyptus or willow leaves through which the sun may be coming, that create this interesting effect.

Artists sometimes use shadow striping to create interesting effects in their paintings and photographs. Once you have found the source of your shadows,you can try making other shadow shapes, and painting or photographing the results!

I don't know the answer to your question, but I'm impressed with your experimental observations.

What happens when you open the curtains just a little, and then a little more? Are the stripes going in the same direction as the curtains or crosswise? How many stripes are there, compared with how many folds there are in the curtains? Can you rearrange the curtains to have fewer folds and see what that does to the patterns?I just visited with Prof. Harry Kroto, who won the Nobel Prize for helping to discover 'bucky balls.' He is working very hard now on bringing science to kids and schools all over the world. He has a website called "The Vega Science Trust."

He showed me part of an online talk about DNA by Armand Lucas that showed how you can shine a laser pointer at a slide with a stack of tiny parallel lines and get a row of dots on the wall.But that works only with lines that are very close together.

One more question - is there a screen on your window? Best wishes, and congratulations on your scientific window research.