- Let's start in early 1857
in a laboratory in Bonn, Germany.
That's where a physicist named Julius Plücker
was working with an instrument maker named Heinrich Geissler
to create odd glass tubes that were according
to Plücker, incomparably beautiful.
Geissler and Plücker didn't know it,
but these Geissler tubes were to change the world.
They were the precursor to not only neon lights
but also cathode ray tubes, also called Crookes tubes.
And without them we wouldn't have television,
oscilloscopes or even X-rays.
Moreover, the cathode ray tube was what was used
to discover the electron.
But how did Geissler tubes work?
Why were they invented?
And how were they changed by Plücker's grad student
and by a man with a fabulous mustache
into the cathode ray tube?
Ready?
Let's go.
♪ Electricity ♪
Geissler tubes started pretty simply.
They were skinny glass tubes with metal electrodes,
platinum wires at either end.
The tubes were mostly evacuated,
had the air removed with a pump
and filled with trace amounts of gas or vapors.
Geissler had just invented a mercury pump
and his friend Ruhmkorff was selling a device
called an induction coil that would produce
very high voltages.
So they had all the equipment needed to do this experiment.
But, how did it work?
Well, when the high voltage was placed across the tube,
some electrons are ripped free of their atoms
leaving positive ions or atoms missing an electron
and the electrons go zipping towards the positive terminal.
On the way, they recombine with the ions
creating visible light.
The color produced depends on the energy levels of the gas
or vapor molecules in the tube,
which is why different gases produce different colors.
You need to have low pressure
because if you have too many molecules,
the electrons don't gain enough kinetic energy
before they bump into an ion
and therefore cannot produce light.
Now, scientists had been making sparks in evacuated chambers
for well over 100 years at this point
in an experiment called The Electric Egg.
In fact, just a few years earlier Ruhmkorff
and his friend Quet had used the spark
from the Ruhmkorff induction coil in an Electric Egg
and had even added various gases or vapors.
What made Plücker and Geissler's experiment so different
is they weren't trying to make a spark
through a vacuum or through gases.
They were trying to electrify the gases directly.
And they were succeeding.
Now Plücker was delighted with the colors
that they were producing but he was mostly interested
in how the light interacted with magnets,
which is why his paper on the tubes was titled,
quote, "About the Influence of the Magnet
on the Electrical Discharges in Diluted Gases".
Catchy, eh?
Geissler, however, saw the financial angle
and started a business selling increasingly convoluted
and beautiful glass tubes to the public as novelty items.
Now, Plücker had a shy graduate student named Johann Hittorf
who 10 years later, noticed that Geissler's vacuum pump
would bubble for hours from an area
that was supposed to be a vacuum.
He deduced the surface of the pump had moisture on it
that would evaporate and make gases.
He therefore used chemical reaction to remove that moisture
and considerably improved the Geissler vacuum pump.
He immediately used it on the Geissler tubes
and found the surprising results.
It seemed like there was a light
coming from the negative electrode
and it would hit the far glass and make it glow,
either green or blue depending on the type of glass.
He then proved that the light
was coming from the negative electrode
by making a special L-shaped tube
and noticing that the glass glowed
across from the negative electrode.
He also found that if he put any object in its way,
it would create a sharp shadow.
Hittorf called these rays of glow
and deduced, quote, "Any point of the cathode
is a source of a cone of rays".
Side note about the term, cathode.
Michael Faraday came up with the terms
cathode and anode years earlier.
Cathode to mean where the electricity came from,
anode to mean where the electricity went to.
Now with a cathode ray tube, the rays of glow
were obviously coming from the negative side.
So, that side was called the cathode
and the positive side was called the anode.
But what were these rays of light?
And why were they being created?
See, electrons from the negative electrode
and from near it were repelled by it
and a few bumped into ions and created the glow.
However, there are less molecules.
So many electrons made it all the way to the far glass,
with enough energy to cause them to glow with a color,
depending on the type of glass.
However, because this light caused glass to fluoresce,
Hittorf assumed it was just another
type of ultraviolet light.
In addition, Hittorf was a reserved man
and not a very good speaker.
So, few people knew of his results.
Now we go to an English scientist named, William Crookes.
In later life, Crookes was most distinguishable
by his completely over the top mustache.
Here is a caricature of him and here is a photo.
Anyway, Crookes came from a truly
enormous upper middle class family.
His father had five children from his first wife.
And ready for it?
16 from his second.
Crookes always loved science and recalled fondly
that he spent his childhood, quote,
"Reading any book of science I could find
and generating smells and destroying furniture."
Although his family was mostly uninterested.
Quote, "I don't suppose any of my family
"even knew the meaning of the word, science,
and I was always regarded a bit of a fool."
Despite his family's distaste,
he went to college and became a chemist.
In 1859 or 1860, he learned of a new way
of studying chemicals by the light they produced
when they were burnt called, spectroscopy.
And used it to discover a new element
he called, thallium for green twig.
He then became fascinated with the relationship
between temperature, light and molecular theory.
In 1869, a talented 16-year-old named Charles Gimingham
became Crookes's assistant.
And by 1876 Gimingham created
a vastly superior vacuum pump for his boss.
Crookes then used this new pump on the Geissler tube
and found very similar results to Hittorf.
Although at the higher vacuums the tube itself seemed black
and only the glass at the end would glow.
In addition, Crookes moved the positive anode to the side
to get it out of the way.
Unlike Hittorf, Crookes was a fabulous speaker.
For example after a talk on the cathode ray tube,
a friend wrote him
that his wonderful experiments were, quote
"Discussed at a thousand breakfasts this morning."
Also, unlike Hittorf, Crookes had a vastly different
view of what was going on inside the tubes.
He didn't think they were beams of ultraviolet light,
he thought they were beams of charged particles
that could cause items to fluoresce.
After all, as Plücker had first noticed
with the Geissler tubes, the position of the rays
could be moved with a magnet.
And magnets were known to move current carrying wires
but do not move beams of light.
To prove his point, Crookes built a tube with a little wheel
inside it and found that the wheel would spin away
from the cathode and towards the anode,
which Crookes attributed to molecular pressure.
In 1879 he wrote, quote "We seem at length to have within
"our grasp and obedient to our control
"the little indivisible particles
which constitute the physical basis of our universe".
What Crookes missed was this radiant matter
wasn't a molecule at all.
For what he was studying,
the cathode rays are really beams of electrons
and electrons are not molecules.
They're not atoms.
They are part of an atom.
They are a subatomic particle, meaning smaller than atomic.
However, Crookes couldn't figure out a way
how to definitively prove that his ray
was made out of particles
nor how to measure its mass or charge.
On the other hand, because of his experiment
with the cathode rays, Crookes actually predicted
the idea of plasma, photons, curved spacetime,
absolute zero temperature
and that mass is related to energy.
All back in 1879, the year Einstein was born.
No wonder his friend Alice Bird told him he seemed, quote,
"Like the magician of the future
before whom no secrets are hid."
Back in Germany, Heinrich Hertz who had used
Ruhmkorff's coil to discover radio was sure
that Crookes was wrong and that Hitorff was right
and that the cathode ray
was really a beam of electromagnetic waves.
And he created an experiment with gold foil
that he thought would prove it correct.
The experiment wasn't as conclusive as he thought
it would be.
But it led directly to the invention of the X-ray machine.
And that story is next time on "The Lightning Tamers".
♪ Electricity ♪
Thanks for watching my video.
Please remember to give it a thumbs up
and subscribe if you haven't.
If you are interested in the history
of how Hertz discovered radio waves,
I have a video about that.
I'm also planning on making a video about spectroscopy
and how that was invented in three or four videos.
And if you're interested in how Ruhmkorff invented his coil,
I actually don't have one on that
because he didn't invent it.
He merely sold ones of very high quality,
so that many induction coils in the 1800s
were known as Ruhmkorff coil.
In fact, he was even given a 50,000 franc prize
in 1858 for creating the most important discovery
in the application of electricity.
Shows what good marketing can do.
However, if you're interested in the induction coil
and how it was invented and how it works,
you should watch my video
on the invention of the Tesla coil,
because two thirds of it is about the induction coil.
Finally, if you've watched my previous videos,
you might have noticed that my old subtitle
was "A Secret History of Electricity."
And my new title is "The Lightning Tamers".
Please put in the comments whether you like
"The Lightning Tamers" better,
whether you like "The Secret History of Electricity" better
or whether you don't like either one of them.
And if you don't like either one of them,
do you have a better idea?
Okay, thanks a lot.
Have a nice day.
(gentle music)