You've heard physicists tell you before that high-speed particles
produced in the sun and other exotic locations are constantly zipping
through your world but it's likely that you've never seen them. Are you
supposed to take what these physicists say as fact without being given
any proof whatsoever? Absolutely not! To prove that these "invisible"
particles do exist and that they are constantly traveling through
ourselves and objects all around us, we'll build a simple detector (a cloud chamber) to
view them using some common items.
Let's start with our bill of materials and where you might find them:
A glass jar with a metal lid:
We're looking for a couple things here: Visibility, a good thermal conducting surface and a tight seal. You'll be using the jar upside-down so less curvy glass near the lid of the jar is better to clearly see the particle tracks. The lid should definitely not be plastic since we want it to get as cold as possible and it should seal the jar pretty well. We're not putting any pressure in the jar but the alcohol vapor we add inside shouldn't have any place to go except in the jar. I used a glass jar from some pickles or something similar. It's the biggest thing I could find with the least amount of curvy glass - you can go bigger if you find something that still suits the requirements!
A swatch of felt:
We're looking to cover the bottom of our glass jar with this felt. Any felt will do. I traced the bottom of the jar on to an old wool sweater that had accidentally run through the wash, cut it out and I had my felt.
Hot glue gun + glue sticks:
This'll be how we attach the felt to the bottom of the jar. Hot glue isn't the only item we can use here but we do need something to make the felt stick to the bottom of the jar. If you're going to use something else, keep in mind that we're going to saturate the felt with alcohol and most tape will unstick after this occurs. If you ARE going to use the hot glue gun, be careful. You definitely do not want burns all over the tips of your fingers (or anywhere else, for that matter) from touching the metal end of the gun.
Black latex paint + paintbrush:
Using a glass jar leaves us with some unwanted consequences, we'll be able to see right through the jar and the particles we're looking for blend in really well with the opaque dry ice that we'll be using. We need to beef up our viewing area with some black paint so we'll be able to see the particles clearly.
A lower container:
We'll be setting our jar in a small container of dry ice. If the walls are too high, we won't be able to see what's happening in our jar. If the walls are too low we might not have enough space to contain the dry ice. I used an empty plastic container from yogurt. You may have to cut your container to fit well. Check the picture below for a better idea of the size of this container
A flashlight:
I assume you know what a flashlight is. Brighter is better. Some people suggest using an old slide projector but I find that it's easier to see the particle trails when you can move the light around to get the best viewing spot. More on this later.
Next, the important parts:
Dry ice:
This might be the most difficult to obtain but definitely not impossible. Lots of things are shipped with dry ice to keep them frozen and then retailers just leave the dry ice to sublime away afterwards. If you catch them at the right time you may be able to walk away with a good amount of free dry ice. HOWEVER, dry ice is really freaking cold. It's sublimation point is somewhere around negative 109˚F. This is easily cold enough to do some damage to your skin or anything else you might touch with it. Use tongs or gloves or some other form of protection when handling it. That said, you should check your local super markets, ice cream stores or anywhere else you can think of that gets shipments of frozen items. One of those places should be able to give you some dry ice or at least tell you where you might be able to find some. You don't need too much, just enough to fill our lower container is fine. You'll either get pellets or slabs of dry ice, both should work equally well although you may have to crush some of the slabs up in to smaller parts to fit around the lid of the jar - we'll cover this in more detail later.
Isopropyl Alcohol:
We'll also need some pure isopropyl alcohol (aka isopropanol or 2-propanol). It's important that you find 99% (sometimes referred to as "Pure") isopropyl alcohol and not 70%. Check the local drug stores for this item. Isopropyl alcohol is not any kind of alcohol you'd want to drink and it's pretty unpleasant to smell as well so keep yourself in a well-ventilated room.
Let's start with our bill of materials and where you might find them:
A glass jar with a metal lid:
We're looking for a couple things here: Visibility, a good thermal conducting surface and a tight seal. You'll be using the jar upside-down so less curvy glass near the lid of the jar is better to clearly see the particle tracks. The lid should definitely not be plastic since we want it to get as cold as possible and it should seal the jar pretty well. We're not putting any pressure in the jar but the alcohol vapor we add inside shouldn't have any place to go except in the jar. I used a glass jar from some pickles or something similar. It's the biggest thing I could find with the least amount of curvy glass - you can go bigger if you find something that still suits the requirements!
A swatch of felt:
We're looking to cover the bottom of our glass jar with this felt. Any felt will do. I traced the bottom of the jar on to an old wool sweater that had accidentally run through the wash, cut it out and I had my felt.
Hot glue gun + glue sticks:
This'll be how we attach the felt to the bottom of the jar. Hot glue isn't the only item we can use here but we do need something to make the felt stick to the bottom of the jar. If you're going to use something else, keep in mind that we're going to saturate the felt with alcohol and most tape will unstick after this occurs. If you ARE going to use the hot glue gun, be careful. You definitely do not want burns all over the tips of your fingers (or anywhere else, for that matter) from touching the metal end of the gun.
Black latex paint + paintbrush:
Using a glass jar leaves us with some unwanted consequences, we'll be able to see right through the jar and the particles we're looking for blend in really well with the opaque dry ice that we'll be using. We need to beef up our viewing area with some black paint so we'll be able to see the particles clearly.
A lower container:
We'll be setting our jar in a small container of dry ice. If the walls are too high, we won't be able to see what's happening in our jar. If the walls are too low we might not have enough space to contain the dry ice. I used an empty plastic container from yogurt. You may have to cut your container to fit well. Check the picture below for a better idea of the size of this container
A flashlight:I assume you know what a flashlight is. Brighter is better. Some people suggest using an old slide projector but I find that it's easier to see the particle trails when you can move the light around to get the best viewing spot. More on this later.
Next, the important parts:
Dry ice:
This might be the most difficult to obtain but definitely not impossible. Lots of things are shipped with dry ice to keep them frozen and then retailers just leave the dry ice to sublime away afterwards. If you catch them at the right time you may be able to walk away with a good amount of free dry ice. HOWEVER, dry ice is really freaking cold. It's sublimation point is somewhere around negative 109˚F. This is easily cold enough to do some damage to your skin or anything else you might touch with it. Use tongs or gloves or some other form of protection when handling it. That said, you should check your local super markets, ice cream stores or anywhere else you can think of that gets shipments of frozen items. One of those places should be able to give you some dry ice or at least tell you where you might be able to find some. You don't need too much, just enough to fill our lower container is fine. You'll either get pellets or slabs of dry ice, both should work equally well although you may have to crush some of the slabs up in to smaller parts to fit around the lid of the jar - we'll cover this in more detail later.
Isopropyl Alcohol:
We'll also need some pure isopropyl alcohol (aka isopropanol or 2-propanol). It's important that you find 99% (sometimes referred to as "Pure") isopropyl alcohol and not 70%. Check the local drug stores for this item. Isopropyl alcohol is not any kind of alcohol you'd want to drink and it's pretty unpleasant to smell as well so keep yourself in a well-ventilated room.
