What Makes Sand Soft? | Hacker News Reader

What Makes Sand Soft?

nytimes.com

60 pointssohkamyung19 comments

Sand isn't soft, at least when you land on it.

As young man I tried jumping down a steep dune ~100+ meters tall. My plan was to run, jump and roll all the way down. I got enough speed and air that I was about 2m up, which is high enough even at steep slope landing on sand to knock the wind out of you. And then I rolled, and bounced, and each bounce hurt. It was like whoosh, oww, bounce, owwww, bounce, owwww, etc. Also, sand in every orifice.

Moral victory: I probably lost 60m altitude rolling.

Also, when people think of sand, they think of beach sand, which is somewhat wet or recently was wet than it have dried, but there is also the variant of very, very dry sand (sometimes can be confused with earth), which is just a little bit softer than a solid ground.

Source: Someone who fell on deserts of Arabia, repeatedly, and almost broke a couple of bones.

Almost a Pyrrhic victory by the sound of things!

https://en.wikipedia.org/wiki/Pyrrhic_victory

Perhaps more of a pyramidic victory in this case, no?

Bravo!

But you did receive a literal crash course on non-Newtonian fluids :)

My best beach was Spiaggia di Is Arutas, Sardegna. It's a white pebble beach, grains arround half arborio rice size. Beach is soft to rest, umbrela still sticks well, wet or dry pebbles do not stick so your skin much. Just brush slighly and you're clean. Way better than sand.

That kind of sand is quite common in (at least) all of the north-western beaches of Sardinia, due to the fact that they are mostly composed of granite and granite is very hard and does not break up easily, I guess.

Still on the topic of sand, but more related to its dynamics than its softness, I would like to recommend the work of Per Bak [1].

Among other things he investigated and modeled the frequency and magnitude of avalanches in piles of sand, work that lead to the concept of self-organized criticality [2].

[1] https://en.wikipedia.org/wiki/Per_Bak

[2] https://en.wikipedia.org/wiki/Self-organized_criticality

This is my first time hearing that Randall Munroe of xkcd writes for the New York Times!

Here's the first one from last November. The illustrations work surprisingly well with the NYT style. [0]

https://www.nytimes.com/2019/11/12/science/randall-munroe-mo...

The whole series can be read via [1]

[1] https://www.nytimes.com/column/good-question-randall-munroe-...

RSS feed: https://www.nytimes.com/svc/collections/v1/publish/https://w...

It reads like GPT-3... And it's not a compliment.

Why?

An uncharacteristically sloppy Venn diagram there, unless I'm missing something.

Some proper subset of industrial engineers don't like sand, and some proper subset of Anakin Skywalker doesn't like sand?

Venn diagrams aren't a good tool for expressing set equality.

More like, among all things industrial engineers feel, and among all things Anakin Skywalker feels, not liking sand is in common

Sure, that's clearly the intent, but it's not what's written. What's written is that those industrial engineers who don't like sand, are also Anakin Skywalker.

No paywall: https://archive.is/DH7zY

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