Main Sequence Page 1
Welcome to the first page of meandering explorations in math, physics,
astronomy, and earth science.
Here is an experimental apparatus,
Version 1, visually kinda interesting but not much going on...
It dawned on me recently while reading
some history that
20th century physics relied heavily on cosmic rays as a source of
. I had
assumed that from Day 1 experimentalists just started building
particle accelerators, starting with electron guns
(cathode ray tubes), that gradually grew bigger and bigger over the
years. While partially correct, fact is it took awhile before
accelerators began evolving into
the monster devices we build
(or don't build
In contrast during the period from 1900 to 1940 or so it
was fortuitous to have a limitless supply of energetic particles
raining down from outer
space as a 'free' source of experimental data. On the down side
this cosmic rain is somewhat random in both direction and content, a
drawback if you want particles to follow a directed path. In that
case a more practical approach is to refine and
sources, permit the radioactive decay products to pass through little
The Wilson Cloud Chamber
The cosmic ray detection story begins with a graduate student trying to
push the boundaries of atmospheric research in the laboratory, an
effort that paid off and led completely unexpectedly to the detection
of subatomic particles. To oversimplify matters: Over the course
of years of diligent effort and development Charles Thomson
Rees Wilson arrived at the device now named for him, the Wilson cloud
This contraption is a sealed volume that reveals moving
subatomic particles through condensation tracks they leave in their
wake like miniature jet contrails in a little
glass jar. It must
have been quite remarkable
to discover tracks drawn momentarily in cloud
chamber mist, like growing up in a huge city and one day discovering it
to be overgrown by an invisible jungle filled with invisible animals.
are my Starting Questions
hard is it to build a cloud chamber?
cloud chamber tracks look like?
What have they to do with
How fast do these particles move?
Can one calculate how long a track should be?
And... well; I have many many questions.
Here are some
tracks I found
described on the web... do these really happen???
Actually I'm jumping ahead here; what do I
know about tracks in cloud chambers beyond rumours? Nothing at
I'll build a cloud chamber and see what happens. So first let's
go after these two front-end
cosmic rays really exist??
and if so...
can be observed concerning their behavior?
(Aren't we unbelievably
fortunate to have come along at such a time and place that we can
answer these questions with a few dollars worth of hardware
and some library books? I think it's incredibly wonderful.)
So let's suppose we're Wilson back
around 1900 at the Cavendish Lab, a conceit I'll make use
of now and again. (This is a good time to mention the Ground Rules for these
passing.) As mentioned, Wilson was a graduate student trying to
atmospheric clouds in glass containers; he was not looking for
subatomic particles. In fact he was pushing the
experimental envelope of cloud research,
forcing water vapor to condense without nucleation sites.
(Clouds... puzzling things aren't they? I'll
little cloud aside.)
Subsequently the 'modern' demonstration cloud chamber has evolved from
Wilson's water-based groundwork. The main difference between what he
was doing and the way cloud chambers are built now is alcohol rather
than water. Alcohol is simpler to supercool so its used as the
page shows how to go about building a cloud chamber using a
box with a black floor in good thermal contact with some dry ice and an
isopropanol-soaked liner. The essential information is here in these
pages as well.
brief pause while I build build build a cloud chamber...
This would be a good time to go read
book for half an hour or so.
ok, all built.
Now to get some dry ice,
rest the chamber on it,
let it sit for 30 minutes or so,
and start looking inside for tracks
The gosh-darned crazy thing
excited about this!
WOW!! THIS IS SOOOO COOOOOL!!!!!
Are, Little Fuzzy Ephemeral
Tracks in the Mist
Here's a picture of one:
ok, gotta catch my breath here...
Bit of Explanation
(if these things are as new to you as they are to me)
First: The above photo is a cloud chamber interior. The gold cubes are
magnets and the glass ampule is a radioactive source. They can be
ignored as they are not essential, just some subsequent ideas after the
initial success. The dark substrate is
shiny because its wet, in fact it is felt that has been soaked with
isopropyl alcohol. And the
horizontal curving diaphanous shape at center left? That's a
track from some sort of invisible thing, some sort of particle zipping
along inside the chamber. It was captured by digital camera perhaps
1/10 of a second after it was created.
Here are some
more remarks on the interior state of the cloud chamber, as well as
how to construct it.
soon as a track forms, it falls and dissolves apart in
second. Hence the cloud chamber is host to an endless sequence of
little phantasms, some sharply and others vaguely defined, tracks that
burst into existence and then in a moment dissolve
away. There are several varieties of these tracks, from little
long straight lines up to perhaps 5 cm in length to veil-like puffs and
and so on; they are quite mysterious. On a couple occasions a huge
track appeared spanning the length of the chamber.
Building the entire apparatus
requires a little time, maybe a couple of hours, and maybe 50USD (or
less if you are resourceful). Also useful is a slide
projector or other strong light source and a dark room and some heavy
books or a big bucket of water. The latter presses the chamber down on
the dry ice ensuring the base is very cold.
Before going any further observationally
I'll document construction
So in answer to the First Question:
There are Invisible Somethings
produce tracks in the cloud
Of course we have no evidence (per claims by
physicists) that the culprits are small charged particles drifting
from outer space, nor do we have any good idea what percentage of them
we are actually detecting. But there's something going on in there.
ideas for further experiments, about six of them. As time and space
I will improve the entries for these ideas; at the moment most are mere
placeholders. The one exception has the asterisks, it's the one about
magnets. There with the first cloud chamber I managed to catch an
- Re-run the experiment paying more attention to setup and
- Carefully observe for awhile to build a little catalog of
powerful magnets to try and bend the particle tracks***.
metal plates that can be charged to create a track-bending electric
field in the chamber.
simple barriers to see if the tracks will pass through them.
radioactive sources to see what sort of tracks they produce.
As I do more reading and learning I will write up some
more complete summary
notes here. The starter-summary is this: I
have an easily-built working device, many ideas on how to improve it,
further experiments to conduct when time permits. So far I believe or
- Cloud chambers primarily catch electrons; cosmic rays are easier
to catch at high
- These electrons could be cosmic in origin, but they could also be
- Considerably more effort is necessary in order to definitively
attribute cloud chamber tracks to
- I really want to continue E-/B-field experiments to see
charge-related path deflections.
- The pandora's box at the bottom of this: Cosmic abundances of
nuclei, which leads to the next page.
The famous planetary scientist Carl Sagan had a television special
called 'Cosmos' which aired in the early 1980s (I believe).
During this program he kept reiterating this phrase
"star stuff" (as well as the
better known "billions and billions").
would insist that we were all made of it, this "star stuff" but I
I never quite
followed his meaning.
Now I think I have it though: I think he
trying to get across a most astounding idea that has emerged from
astrophysics in the 1930s through the 1950s (in my view): the cosmic
hydrogen and helium--and therefore our own carbon-based
the alchemy within a
fact within the zillions of stellar
furnaces that have caught fire and burned
nuclear fuel into ashes over the past 13.7 billion years (aotu).
Simple enough to make the claim, but really I would like to understand
the argument on a