What would a beach look like if prolonged exposure to humans made the sand change color?

Question

So one of the supernatural elements in my urban fantasy story is a system of "aura-syncing" that explains how various supernatural abilities extend to one's clothes and belongings. A full explanation can be found here.

Tl;dr: Every human projects an invisible aura 3 inches from their body, and any solid object that spends 5 minutes completely encased in this aura becomes "synced" to that aura and is treated as a part of their body for the purpose of various abilities as long as it's at least partially within their aura when that ability is used. The aura an object is synced to will be changed again the next time it spends 5 minutes encased in a new aura.

Now, the main character is one of a few people on Earth who has the ability to see these auras. When he uses this ability, the entire world turns pure white with these sort of cell-shaded borders, and the only things that have any color are human auras and any objects that have been synced to an aura. Every person's aura actually has a color assigned to it, which can be absolutely anything except white (or any color too close to white for the average human eye to distinguish), though darker colors are rarer. And the main character will see any synced objects as being the same color as the aura of the person it's synced to.

Now, the fact that this applies even to the tiniest particles or grains of sand is a pretty crucial plot point, and it got me to start imagining what a beach would look like in this "aura vision", with every single grain of sand a human's ever sat near for five minutes being imprinted with that human's unique color.

Right away it sounds like a really striking image, with a technicolor pattern of human bodies imprinted into the sand from all the beachgoers lying down on it, slowly eroded by the sand being kicked around until the colors mix together, only to all be re-imprinted again. But I was wondering if there'd be anything else to the picture.

Is there anything about how sand moves and scatters on a beach that would cause other patterns to emerge, or anything else that would affect what my protagonist would see?

Answer 1

I remember you original question --- very interesting!

As for the sands of the shore, I honestly don't think the effects will be quite as spectacular as you might be hoping.

Some possibilities:

1. Ideal situation is where there is a calm sea and no breeze to speak of all on a warm day that is a holiday during beach season. This will give you maximum number of people with a minimum of sand movement. If your aura-sighted person knows what colour, hue and saturation to look for, she will be confronted by thousands of latent impressions. The people that stayed (in one place) the longest and were the last to leave, will naturally leave behind the most pristine impressions. She might be able to see a more saturated area that represents the torso with perhaps smaller patches where the head and arms and feet rested. Other impressions will be less clear: if someone laid on the sand for a couple hours, relatively late in the afternoon, and then left, chances are good his impression will be at least somewhat disturbed. People running might churn up portions of the impression, but she should still be able to make out a blobby outline at least.
2. Less Than Ideal Situation is weather conditions as above, but the person in question lay on the beach during the morning and then got up to leave around noon when once the place became too crowded. Chances are very good her colour sand will be churned up and locally scattered. Perhaps built into a sand castle along with other people's sand who were lying nearby. Our aura-sighted girl will find it very difficult to determine what the actual colour scheme is. She might be able to get a general description like "greenish", but it will mixed in a three (or actually four) dimensional cloud of other colours and saturations.
3. Least Ideal Situation is where an early morning person lay on a very popular spot that was eventually taken over several times during the day and also got churned up, built into sand castles, which got dashed down and scattered, and then smoothed over again.

Note also that for each of these ideal situations, our aura-sighted girl will have to contend with particles that have been synched on the days and weeks previous.

1. Very Likely Situation is where our girl will have to contend with normal seaside weather. Beaches are very labile. They don't stay in one place. The sands are constantly shifting as winds blow them this way and that. Tides cause sand to be heaped up and drawn away again. If she takes a look at the beach on a windy day after the tide goes out again, she'll be confronted not only by the churned up and commingled colours of the day and the days previous, but also the colours of sands that the winds have exposed from higher up and the sands that the waters have deposited on the beach. The longer she delays, the more the beach will evolve and obscure any impression she might have been able to make out.
2. Worst Case Scenario is of course that her investigation has been hampered by very bad weather. Hurricane Sandy is about to visit the Big Pomegranate and the beach is inaccessible. By the time our aura-sighted girl can get out there, there is simply no beach. All the synched sand has been washed out to sea. Looking out into the water itself will be no help, as her sight will be blurred by all the water molecules that have become synched to hundreds of millions of people all across the eastern US whose (treated) piss & bath water has made it out to sea...

PS: you can buy coloured sands in most any craft shop. Buy a few different kinds and mix em up in a jar. See for yourself what our girl will see!

PPS: EDIT --- I'd imagine that even the very best case scenario impression will look something like a luminol image:

http://truejustice.org/ee/images/perugia/frontpage113/11355.jpg

And being a popular beach, image upon image upon image.

Answer 2

A three inch radius and five minute exposure time required for aura syncing means that the vast majority of beach sand would stay sand colored. Only on popular beaches in places like California, Florida and Hawaii where lots of people go and lay in the sun would you see colored blotches of sand.

The protagonist would see human-sized stripes of sand where people lay. After the people get up and leave, these stripes would eventually get smudged (during the night, during weekdays when there are fewer sun worshipers, etc).

High tides, wind and storms would also mix the surface sand. Over the long term, you'd get a smudgy mixture of white and sand.

Remember, though: due to the three inch radius and five minute exposure time required for aura syncing, the vast majority of sandy beaches would just stay sand colored, since so many people go to the beach and play (in the surf, on the sand, etc) instead of just laying there.