Shabbat - Lights
Stories exist in Rabbinic lore about shivering Karaites
eating stone-cold food
huddled on the floor in a dark room over Shabbat. While there is some
historical truth to this story, there is also a great deal of myth -
to the story's persistence.
The Torah does, in fact, prohibit the burning
fires on Shabbat. As above, Ex. 35.3 (this time in Hebrew): Lo'-Teva`aru
BeKhol Moshevoteikhem BeYom HaShabbat.
You shall not cause a fire to burn in all your settlements
on the Sabbath day.
The word 'Tav'aru' comes from
the root word 'ba'ar,' which means to burn. Consequently, what we are
doing on Shabbat is burning fire - or having a fire burning.
may be raised, how does this apply to light bulbs? Those familiar with
Rabbinic prohibition not to turn on and off lights will find a different
prohibition herein discussed.
To best address the issue at hand, one must first understand the elements
is dealing with.
The following paragraphs will explain the elements
factored into the discussion at hand: Fire, incandescent light bulbs,
fluorescent light bulbs.
Fire is a chemical reaction in which a combustible fuel reacts with
release large amounts of thermal energy. Many atoms bind very strongly
oxygen atoms and these fuel atoms release energy when they bind with
Initiating these combustion reactions normally requires some thermal
get started. This starting energy is known as activation energy. That's
have to light the fire--you must provide the activation energy. After
each oxidization reaction produces the activation energy needed to start
another oxidization reaction and the fire keeps itself going until it
consumed all of its fuel.
A normal incandescent lamp contains a double-wound tungsten filament
gas-filled glass bulb. A double-wound tungsten filament is a very fine
that is first wound into a long, thin spiral. This spiral, then, is
a wider spiral. While the final filament looks about 1 or 2 centimeters
it actually contains about 1 meter of fine tungsten wire. When the bulb
turned on, an electric current flows through the filament from one end
other. The electrons making up this current carry energy, both in their
and in the forces that they exert on one another. As they flow through
tungsten wire, these electrons collide with the tungsten atoms and transfer
some of their energy to those tungsten atoms. The tungsten atoms and
filament become extremely hot, typically about 2500° Celsius. Tungsten
used because it tolerates these enormous temperatures without melting
because it resists sublimation longer than any other material. Sublimation
when atoms "evaporate" from the surface of a solid. The gas, argon,
bulb is there to slow sublimation and extend the life of the filament.
[Ar] is a monatomic, chemically inert gas composing slightly less than
the air. Its gaseous specific gravity is 1.38 and its boiling point
degrees F (-185.9 degrees C). Argon is colorless, odorless, tasteless,
non-corrosive, nonflammable, and nontoxic.)
Once the filament is hot, it tends to transfer heat to its colder surroundings.
While much of its heat leaves the filament via convection and conduction
gas and glass bulb, a significant fraction of this heat leaves the filament
thermal radiation. For any object that is hotter than about 500° Celsius,
of this thermal radiation is visible light. For an object that is approximately
2500° Celsius, about 10% of the thermal radiation is visible light.
most of the filament's thermal radiation is invisible infrared light.
can feel this infrared light warming your hand, you can't see it. Only
80% of the electric power delivered to the bulb becomes thermal radiation
only about 12% of that thermal radiation is visible. Consequently, an
incandescent light bulb is only about 10% energy efficient.
lamps, including fluorescent and gas discharge lamps, are much more
A fluorescent lamp tries to produce light without heat. It collides
with mercury atoms to produce an atomic emission of ultraviolet light.
ultraviolet light is then converted to visible light by the layer of
phosphor powders on the inside of the lamp's glass envelope. In principle,
whole activity can be performed without creating any thermal energy.
many unavoidable imperfections cause the lamp to convert some of the
energy it consumes into thermal energy. Nonetheless, the lamp only becomes
rather than hot.
At first glance, it may appear that both fluorescent light bulbs and
incandescent light bulbs would be permissible for use on Shabbat. Neither
produces a flame to generate light. Consequently, they would not violate
Tav'aru. However, the tungsten filament in an incandescent light is
burns the same way a glowing coal burns. In the case of the coal, carbon
monoxide and carbon dioxide inhibit it from flaming. In the case of
tungsten filament, it is the argon. However, the argon doesn't keep
filament from burning all together. In fact, when a bulb blows the filament
burned so thin that the amount of heat generated in it causes it to
so briefly) and totally burn through. The thinner the filament the less
electrical energy it takes to cause it to flame. The argon only inhibits
flaming on a newer filament because the thickness of the filament in
presence of the argon doesn't allow it to get to the flash point, but
filament burns, it gets thinner and thinner.
conclusion, from this we learn that incandescent lights are prohibited
for use on Shabbat, but fluorescent lights are permitted. Also,
keep in mind that because we are not allowed to engage in commerce over
Shabbat, so we are also prohibited from using electricity from the
electric company. Lights operated on Shabbat should be battery
operated, or solar.