How is it possible that atomic particles, which are not visible, can form trails which are visible? I guess I’m thinking about an apparent conflict between why atoms are invisible (i.e.: smaller than an angstrom, or words to that effect) AND THEN, wouldn’t the same be true for the width of trail of these particles…or sub-atomic particles??? Please explain and/or correct me, as needed… - Jinx 
Think of a boat going through the water. Even if you’re so high up you can’t see the boat, you can still see its wake - the waves spreading out from its position.
IANA nuclear physicist, but that’s the concept, as I understand it.
More accurately, think of jet aircraft flying at high altitudes. You can’t see them with the naked eye, but their contrails are eminently visible. It’s actually a very similar principle at work.
Smeghead, hmm…but the pictures I’ve seen of these trails are sharp, clearly-defined arcs. I don’t see the widening wake pattern. As I am to understand your analogy, (explaining why "now you don’t see it, now you do…being directly related to the widening “wake”), wouldn’t these arcs be anything but sharp and clearly defined??? - Jinx
A-ha! Thanks to the supplemental posts shedding more light on the sunject. The vapor trail example and almost parallel phenomena makes sense. I wonder if this was discovered by accident somehow, or did someone reason out that we might be able to capture evidence of the existence of these particles in this fashion? - Jinx
If you seriously want to explore this, you can build one.
In a homemade chamber, you’ll see that the trails start out sharp, but get all drippy and wider after a few seconds.
The high-energy particles don’t create the trails directly.
Instead they collide with air molecules, knocking electrons off which are captured by adjacent air molecules. You end up with a trail of electrically charged molecules, little “plusses and minuses.” In chilled moist air the water molecules would condense into droplets if only they had some kind of “seed” to condense upon. Charged molecules, though incredibly tiny, provide such a “seed,” and the water droplets quickly grow thousands of times larger than the original charged atom.
Search on “Wilson’s Cloud Chamber.” The articles mention that Wilson developed the device to study weather physics. I bet that he accidentally observed all sorts of mysterious trails in his “clouds” and that’s how the whole subject got it’s start. (I imagine.)
The environment is full of radioactivity, mostly coming from above as cosmic rays, so if anyone should operate a “cloud chamber” they won’t just get a simple cloud, instead they’ll get a mass of little lines where the lines are tracks of cosmic ray particles.
Don’t take that bet. By his own account, Wilson hypothesised that particle tracks would be visible in his old cloud equipment and then looked for them.
Further to Squink’s comment, no amount of awe at the scale of a modern particle detector, installed in its pit reading vast amounts of data, quite matches the eerie spectacle of whispy trails dispersing in a little cloud chamber.
A link with instructions on building your own cloud chamber.
And posts testifying that all the majest of the universe can be glimpsed through alcohol vapor in a clear box.
I LOVE THIS BOARD!!!