Why are Dust Particles Moving in a Specific Direction in a Sunlit Car?

In summary, according to the person, they observed particles of dust slowly moving around in a westward direction, despite having a degree of random motion. They hypothesized that the Earth's magnetic field may have been responsible, but could not yet explain why this would be the case.
  • #1
Skoth
7
0
I am a curious (or perhaps bored!) fellow, and as such I noticed something peculiar recently. I was sitting in a car in a garage. The car was stationary and off, and it was facing the east. The sun was beginning to set in the west and a light shone through the back window shield. In the rays of light, I could see particles of dust slowly moving around. The thing that struck me is that, although they also had a degree of random (Brownian?) motion to them, they all appeared to be moving to the west, in the direction of the sun. The impression I'm under is that these particles should all be moving randomly, period, and should have no general direction.

I've only taken two awesome semesters of calculus-based physics. In spite of my knowledge could not come up with an explanation for what I saw. I spoke with a friend about it and she suggested that the Earth's magnetic field may have had something to do with it. And while I like to keep an open mind, I feel that that cannot be the case since I live in California, and the magnetic field would cause these particles to move either north or south (and if these particles were moving according to that notion, wouldn't that make them monopoles!?).

Is there a physical phenomena to explain my observation?
 
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  • #2
Skoth said:
I am a curious (or perhaps bored!) fellow, and as such I noticed something peculiar recently. I was sitting in a car in a garage. The car was stationary and off, and it was facing the east. The sun was beginning to set in the west and a light shone through the back window shield. In the rays of light, I could see particles of dust slowly moving around. The thing that struck me is that, although they also had a degree of random (Brownian?) motion to them, they all appeared to be moving to the west, in the direction of the sun. The impression I'm under is that these particles should all be moving randomly, period, and should have no general direction.

I've only taken two awesome semesters of calculus-based physics. In spite of my knowledge could not come up with an explanation for what I saw. I spoke with a friend about it and she suggested that the Earth's magnetic field may have had something to do with it. And while I like to keep an open mind, I feel that that cannot be the case since I live in California, and the magnetic field would cause these particles to move either north or south (and if these particles were moving according to that notion, wouldn't that make them monopoles!?).

Is there a physical phenomena to explain my observation?

I think there was a very slight "wind" moving the particles. The side towards the sun is hot, the other side cold. This will set up a circulation, heated air rising on the sun side,moving backwards across the top of the car, down the back, and forwards along the lower part of the car. You might have been looking at the lower air currents. Take an incense stick or cigarette and hold it in different places and watch which way the smoke goes after it stops rising, see if that theory is correct.
 
  • #3
Nothing magnetic is likely, nor electrostatic. Just plain old convection currents.

Brownian motion is much smaller scale than you can see under those circs. I think. What you could see would have been turbulence and any apparent mixed motion of particles going in different directions would probably be an illusion due to mass motion of particles at different distances from your eye.
You need a microscope to see Brownian Motion, afaik.
 
  • #4
Ah, I didn't even think of heat conduction. I guess that makes sense why I didn't though: thermodynamics was my worst section!
 

What causes dust particles to move?

There are several factors that can cause dust particles to move, including air currents, temperature changes, and human activity. Wind is the most common cause of dust particle movement, as it can pick up and carry particles over long distances. Temperature changes can also create air currents that cause dust particles to move. Human activity, such as walking or sweeping, can also disturb dust particles and cause them to become airborne.

How far can dust particles travel?

The distance dust particles can travel depends on the size and weight of the particles, as well as the speed and direction of the air currents carrying them. In general, smaller and lighter particles can travel farther than larger and heavier particles. Dust particles can travel anywhere from a few feet to hundreds of miles.

What impact do dust particles have on air quality?

Dust particles can have a significant impact on air quality, especially in areas with high levels of pollution. When inhaled, dust particles can irritate the respiratory system and cause health problems, particularly for people with respiratory conditions like asthma or COPD. Dust particles can also contribute to haze and reduce visibility in the air, affecting overall air quality.

How do dust particles affect the environment?

Dust particles can have both positive and negative effects on the environment. In areas with high levels of dust, plants may struggle to grow and thrive due to reduced sunlight and increased levels of dust settling on their leaves. However, dust particles can also have a positive impact by carrying nutrients and minerals to different areas, contributing to the growth of vegetation.

Can dust particles cause allergic reactions?

Yes, dust particles can cause allergic reactions in some individuals. When inhaled, dust particles can irritate the respiratory system and cause sneezing, coughing, and other allergy symptoms. People with dust allergies may experience more severe reactions, such as asthma attacks, when exposed to high levels of dust particles.

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