How do light bulbs work?
By any standard, the invention of the light bulb was a real light bulb moment.
[Ping!]
And it didn't come a moment too soon.
Because although we'd known how to produce electricity through chemical reaction since
1800, and how to generate it mechanically since 1831, thanks to Michael Faraday, there
just weren't very many uses for the new force, other than impressing other Victorian scientists
by using it to make sparks and flashes.
Of course, the early electrical pioneers were bright [geddit?]
enough to realise you could use an electrical current to make a wire glow -- and if you
made a thin enough piece of wire with a high enough melting point then it would glow white
hot.
This is because, in pretty much the simplest possible terms, the atoms in the metal release
some light photons when their electrons become excited by the electrical current.
The problem with using these glowing wires as a source of light became obvious after
a couple of minutes really.
Exposed to the oxygen in the air, they would quickly oxidise and disintegrate.
The light bulb was the solution: a see-through sleeve to protect the hot wire.
Like many good ideas, it had many fathers.
Indeed, the light bulb as we know it was invented pretty much simultaneously on both sides of
the Atlantic in the 1870s, by Joseph Swan, who was British, and by Thomas Edison, who
wasn't.
And the basic idea has barely changed since.
The light bulb is made out of very thin glass, and contains a wire filament made from a metal
chosen to have a very high melting point -- usually tungsten, wound around in a coil pattern.
Early light bulbs contained a partial vacuum, the space around the filament was emptied
of most of the air, reducing the potential for an oxidising reaction to take place.
More modern bulbs switched over to the use of an inert gas (one that doesn't react with
the white hot element) for the same effect.
The result is a bulb that could provide up to 1000 hours of light at the flick of a switch,
and sometimes considerably more.
One that was manufactured in 1883, just five years after the light bulb was invented, is
still in daily use in the UK, 130 years later.
America claims another light bulb that's been switched on continuously for 109 years.
But for all its ubiquity, the light bulb isn't what you'd call an advanced piece of kit.
Even its name is a bit of a misnomer -- we should probably call it the heat bulb, as
over 90 per cent of the energy it consumes is converted into heat.
Visible light is really just a by-product.
It's why old fashioned light bulbs get so hot -- useful if you're making an incubation
cage for some chickens, or trying to heat a student flat when your landlord has turned
the gas off.
But not really ideal.
Which is why the humble light bulb has become a threatened species in recent years.
More modern compact fluorescent 'energy saving' light bulbs are four times more efficient
for producing the same amount of light, and the new generation of LED-based lights are
more frugal still.
The production and sale of the old incandescent light bulb is now regulated in many countries,
with believers in the old ways having to buy in stocks of bulbs for the future.
Like in the war.
And it's not just in homes and schools and offices that the light bulb is running out
of time: Mercedes recently launched a new car that doesn't have a single bulb in it,
every bit of illumination (including the headlights) is done by LEDs.
That in fact was their big light bulb moment.
Except obviously it was LED.
LED moment, sounds a bit feeble doesn't it.
What will cartoonists do if they can't draw a glowing light bulb over a boffin's head
to indicate a good idea.
LED moment, doesn't have quite the same ring to it, does it?