The physics of sand castles: Just add water

A day out on the beach would be incomplete without a sand castle. The mightier the castle, the better. But sand is next to useless as a building material. Without water it simply spreads out as wide as possible. So in search of a good recipe Daniel Bonn, a physicist at the University of Amsterdam, and colleagues have stumbled upon a formula for making the perfect sandy redoubt.

As they reveal in a paper published this week in Scientific Reports the key is to use sand with only 1% water by volume. Wet sand has grains coated with a thin layer of water. Owing to water’s surface tension this thin coat acts like skin stretched over many grains, holding them together by creating bridges between the grains. The strength of these bridges is enough to fight Earth’s gravity and prevent the structures from buckling under their own weight.

An easy way to achieve the right amount of water, Dr Bonn suggests, is to tamp wet sand in a mould (open at the top and the bottom) with a thumper at least 70 times, as he did in his experiments.

As for the design itself, unsurprisingly, the wider the base the taller the castle. According to calculations, using ideally moist sand, a column with a three inch diameter could rise as high as two metres. At 12 metres, the current world record for the tallest sandcastle, set by Ed Jarrett in 2011, used a base of roughly 11 metres. If Dr Bonn is right, sand engineers could in principle beat that with a castle thrice the height upon the same foundation.

First published in The Economist.

Image from here.

#ediblepeople: What an idea!

For those new to twitter or not aware of it, ‘#’ symbolises a hashtag. Using which we can track people tweeting about a particular topic. Last time I enjoyed a hashtag as a much as I did today it was #tweetlikesagarika (after Sagarika Ghose from CNN-IBN). Today it is #ediblepeople, @rameshsrivats who thought of this idea is a pure genious.

My contributions:

  • Pulao Picasso
  • Muhammad Thali
  • Kheema Chaudhary
  • Kofta Annan
  • John Lemon
  • Kulfi Annan
  • Coco Caramel
  • Stephen Fry
  • Leonardo Do Pyaza
  • Edible Murphy
  • Chilly Clinton
  • Arnold Schezwan

Here’s my favourite list:

  • Sagarika Gosht
  • Robin Uttapam
  • Kishore Biryani
  • Mutton Tata
  • Leander Peas
  • Chunky Soup Pandey
  • ChikooShake Bachchan
  • Salmon Khan
  • Shashi Khajoor
  • Paresh Chawal
  • Malai ka Sheera Wat
  • Bharta Dutt
  • Ladoo Prasad Yadav
  • Rabdi Devi
  • Kris Shrikhand
  • Anupam Kheer
  • Aam Admi
  • Rajma Sardesai
  • Jenson Mutton
  • Soup Dogg
  • Brad Pitta
  • Gerhard Burger

You can follow the excitement here.

White wonderland

The highlight of my return to the UK this year was definitely the snow. The moment our plane broke through the clouds and we could see heathrow from the window, I was awestruck. Everything was white, it looked so pristine from the plane. The journey from Heathrow to Oxford was equally mesmerizing. Although, it had been almost 30 hours since I’d left home and had had hardly any sleep, the views of the white wonderland did not let me wink. I even managed to tweet a poem!

Exeter college chapel

It snowed a little more today and I could not stop myself from taking pictures. Here you will find a link to the rest of the pictures.