Tuesday, 18 September 2012

Home made breasts and custard

As anyone who has spent more than a tiny amount of time there, the Halfbakery (my favourite ideas bank) has long been obsessed with custard.  There are custard-filled speed bumps, custard travelators, ustard (which becomes either custard or mustard depending on what you prefer), custard as a coolant and custard guns.  The main reason for this obsession is that custard is a non-Newtonian fluid.  Newtonian fluids are ideal and probably don't exist, but water is close to one:  the harder you hit it, the more it yields, on the whole.  Plot the stress rate against the strain rate on a graph and you get a straight line.

However, many fluids are non-Newtonian.  They may hit back when you hit them hard or start off not yielding but decide to do so later, or they may go the other way and yield less than expected when you hit them gently, or trickle out gradually as time passes.  Examples of non-Newtonian fluids are blood, ketchup (think of banging on the bottom of the bottle to get it out or turning it upside down back in the day), non-drip gloss paint, wet cement, silly putty, quicksand and, famously, custard.

Custard, or rather  a mixture of cornstarch and water called "oobleck" after a Doctor Seuss story, is an old home ed standby.  It's possible to jump on it without sinking in but not to walk on it in the same way.  This means, for example, that you can let your hand sink into a jug of oobleck and then lift the jug by raising your arm.

The soft, yielding parts of the human body are often also non-Newtonian, notably women's breasts.  Convincing artificial breasts are therefore not good if they're just made from balloons inflated with air or water.  It would be better to make them with custard:



That didn't go particularly well.  Nor did it go particularly badly.

Here's a second video on the evolution and social significance of breasts and breastfeeding:




Not sure how that went yet as i've not edited or watched it.  Anyway, the main point of this video is to talk about why humans have breasts and the evolution of breastfeeding, along with the significance of female breasts in Western culture.

More generally, i'm working on coming across more spontaneously, and that at least seems to be going well.