I seem to remember a TV programme presented by Professor Brian Cox (swoon....I think he's absolutely gorgeous!) using two slits and a light beam. But I couldn't quite understand the concept. He usually explains things is a simple way, but I must have been extra-dim that evening.

My view on privacy is that the more one raises one's profile online and in the Press etc, the more there is of you 'out there'. And if one is utterly boring to the snoopers (as I am), there's not much to discover. However, I do worry about scammers getting hold of my bank details and identity. I heard that it's not difficult to find someone's password, and that there are 'strong' and 'weak' ones.

When my husband applied for a British passport many years ago, we noticed a car parked at the T junction facing our bungalow, with a chap watching our comings and goings. When my husband popped out to the corner shop for the paper, the chap drove off. In a small village he was very conspicuous. Sure enough, at the Passport interview, the very same man was behind the desk! I found this quite sinister, but they needed to know the residential address was correct.
I can't imagine what pleasure people get from Facebook or Twitter etc.
I'm not a bit interested in photos of people's cute dog or new baby, or their choice of wallpaper.