But actually, what is dust?

Posted on Feb 15, 2022

A table is table, a chair is a chair, and a lamp is, indeed, a lamp. At least from a broad perspective. You are also describing a lamp when saying “an illuminating device, generally composed of a stand and a bulb” The stand and the bulb are as much lamp as the object itself, but at the same time, completely different entities.

The whole world is built by these types of constructions. If stubborn to break an object down into its building blocks infinetly, you will eventually reach atoms, protons and even quarks.

I usually enjoy breaking things down. Its usually an easy and entertaining task that helps me understand things better. Really recommend it to achieve comprehension. Its fun, as long as you don’t get stuck 😃.

Hence, dust is not fun. We all know what dust is. At least broadly. Now try to describe it. Break it down to its building blocks. Not so easy, right?

You can probably reason dust is composed of suspended particles. Very small particles of no specific material. Yet we both know, this is not good enough. If we really want to understand dust, we need to understand what makes up dust.

Dust, the basics

⚠️ DISCLAIMER. I will focus on airborne dust. Static dust is a bit boring 😏

Dust is described by the National Geographic Society as “a collection of microscopic particles of material” [1]

The World Health Organization describes such particles to be between 1 and 1000 μm (that’s 0.001mm or 10-6 for the smallest, 1mm or 10-3 for the biggest) [2]. In other words, very small, only the biggest visible easily percieved by the human eye.

It is not easy to classify particles this size. A block of wood is clearly wood, but what about a 0.01mm piece of wood? Would you be so sure about its composition after examining it?

What’s more, dust is not homogoneus through space. Dust inside you house is different to dust in a construction site and unrelated to dust in space. I’ve found house dust and space dust are the most interesting, so I will focus on them.

Home dust

A study conducted by Paloma Beamer found that house dust composition depends considerably on the ocuppants’ habits. Around 60% is brought from the outside, stuck to clothes, hair and the soles of your shoes.

As a consequence, home dust is mainly composed of “foreign” materials: pollen, dirt and, yes, dust mites (tiny pests that feed on dander and dead skin).

Hence why dust can be so annoying to people with allergies. Fun fact, dust mites where not a problem until the popularisation of textiles and cloths in homes.

However, dust is not only external: it can also be sourced inside the house. Small paint particles, bits of fiber and, drumroll please, dead skin! However, for those who claim dust is composed mostly of dead skin celss, I’m sorry to break down to you that it’s not. Most of these particles end up washed away when you shower or are left outised your home door.

Space dust

Space dust is probably the entity that has most triggered my curiosity recently. When reading Isaac Asomov’s the Universe, I came to notice “space dust” is a recurring character that apparently plays a leading role in the story of our universe.

When it comes to your home, it is relatively easy to wrap your head around the fact that small particles of various materials may break off. The origin is easy to explain. But when it comes to the emptiness of space, where did this dust come from?

Space, or cosmic dust, has a more defined classification than home dust. Astronomers usually classify it according to its location. Hence, intergalactic dust is found between galaxies, interstellar dust is suspended in galaxies and within stars, and circumplanetary dust lays between planets.

When talking of space, size metrics become different to the ones used on Earth. What on our Earth may be considered massive may be a ridicule particle on space-scale. This explains why bigger particles in space can be considered dust. Even a one meter wide meteoroid could be considered space dust!

Dust was at first anoying for researchers, as it screened observers from their objects of interest. However, as time passed by, dust proved to be an excellent source of information on the formation of the universe.

Particles that make up space dust usually are made of rock, ice, minerals or small organic compounds (sometimes a combination of the above). Of these, rock and carbon rich grains make up most of it inside the Solar System, but when leaving the Sun’s warmth behind, ice becomes the main character. That answers the why, but what about the where?

The Cosmic Dust Analyzer project (CDA), which focused on dust surrounding Saturn, concluded, that, although an explanation for origin could be found in our system, some particles where concluded to be interstellar. Some dust particles travelled millions of kilometers! To get to Saturn! (boring trip, I guess)

If this doesn’t blow your mind, well, I don’t know what will. Well, maybe the fact that more than 100 tons of dust rain on the Earth every day.

Carl Sagan correctly said “We are made of star-stuff”, and that star-stuff is space dust that evolved into more complex organisms. In other words, we are dust. So are stars, planets, meteors… or at least they were millions, if not billions of years ago.

More than just ‘dust’

Personally, I find dust to be beautiful. Matter lives in a constant cycle breaking down to then come back together. In the center of it all: dust.

The truth is dust can be used as an opener to many essential questions about the universe. Whether you are trying to find answer about its origin, its composition or its structure, these small particles are bound to appear.

It is intriguing how something so small can cover something so big (the “emptiness” of space, which is, indeed, not empty). Yet it exists hidden to most minds which simply don’t want to make the effort of questioning their surroundings. It is sad.

I hope that you, dear reader, have opened a door in your brain that lets your curiosity out. Dust is just one example of the millions of unanswered questions we incomprehensibly take for granted. Don’t be like the crowd. Start making questions, even if it’s on stupid things like dust.

References

[1] Dust National Geographic Encyclopedia 🔗

[2] Hazard Prevention and Control in the Work Environment: Airborne Dust World Health Organization pp 1-3 🔗

[3] Is Dust Mostly Dead Skin? Veritasium 🔗

[5] Dust, Unsettled Janet Pelley 🔗

[6] Be Glad You Don’t Have to Dust in Space NASA tumblr 🔗

[7] Getting a Handle on How Much Cosmic Dust Hits Earth Nancy Atkins 🔗

[8] Seven grains of interstellar dust reveal their secrets Andrew J Westphal on Science 🔗


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