Understanding Light Particle Theory Take The early Greeks by benbenzhou


									        Understanding Light:
       Particle Theory, Take 1
The early Greeks supposed that light was
streams of particles of the element of “fire”
which flew from the eye. (Paul, 1898)
In 55 BCE, Lucretius wrote that light was
composed of minute particles which fly through
the air. (Lucretius, 1994)
Ibn Al-Haytham (Alhazen) published his Book of
Optics in 1021, wherein he described light as
streams of tiny energy particles. (Gribben,
        Understanding Light:
        Wave Theory, Take 1
Descartes supposed that light was waves,
caused by disturbances in the “plenum.” (Smith,
In his Treatise on Light, published in 1690,
Huygens proposed that light was made up of
waves, much like sound, in the “Luminiferous
Aether.” He also suggested that since light is
not affected by gravity, it should travel slower in
a denser medium. (Potter, 1856)
        Understanding Light:
       Particle Theory, Take 2
Newton published Opticks in 1704, with the
corpuscular theory of light. His theory correctly
accounted for reflection, but not refraction. He
postulated that light particles would accelerate
in denser mediums as they were subject to
more gravitational pull. (Newton, 1704)
Laplace went a step further, postulating that
there could be an object so massive that its
gravitational pull would prevent light from
leaving it. (Thorn, 1994)
        Understanding Light:
        Wave Theory, Take 2
In 1801, Young demonstrated interference in light,
proving it to be a wave. (Bunch, 2004)
Fresnel presented his own wave theory of light in
1817. By 1821 he had shown that polarization
could only be explained if light were composed of a
transverse wave. (Hannavy, 2002)
In 1850 Foucault made the first sufficiently
accurate measurements of the speed of light
through differing mediums, supporting the wave
theory and spelling the end of Newton's
corpuscular theory. (Cassidy, et al., 2002)
       Understanding Light:
     The Wave-Particle Duality
In 1873 Maxwell described light as an electro-
magnetic field, obviating the need for a medium in
which to travel, while the Michelson-Morely experiment
in 1887 disproved the existence of a static “Aether.”
(Bunch, 2004)
In 1900 Planck's theory for black body radiation solved
the “ultraviolet catastrophe,” but relied on light being
made of discrete particles. (Spangenburg, 2004)
The wave theory could not explain the photo-voltaic
effect and the particle theory could not explain
interference. Today it is understood that light behaves
as a particle or a wave depending on what aspect one
is measuring. (Bunch, 2004)
     The Solar “Superstorm” of 1859
   On the night of August 28, 1859, a massive
    auroral event occurred, visible directly overhead
    as far south as Cuba and Hawaii (Savage,
    2003), and visible far above the horizon from
    ships near the equator (Odenwald, 2008).
    Meanwhile, magnetometers worldwide shot off
    the scale.
   On the day of September 1, 1859, Richard
    Carrington, an English astronomer witnessed a
    brilliant white flare originating from two locations
    in the unusually large sun-spot group he was
    sketching (Odenwald, 2008).
     The Solar “Superstorm” of 1859
   September 2, 1859, just seventeen hours and forty
    minutes (Savage, 2003) after Carrington's sighting
    of the flare, a second, even more massive auroral
    event took place, visible overhead as far south as
    Panama. Gold miners in the Rocky Mountains
    were awakened by the light at 1:00 am and began
    to have breakfast, thinking the sun was rising
    behind a cloudy sky (Odenwald, 2008).
   Telegraph stations were subjected to high-voltage
    electrical discharges, resulting in reported near-
    electrocutions and several telegraph stations
    actually burned down (Odenwald, 2008).
     The Solar “Superstorm” of 1859
   Prior to the events of August 28 and September
    1 and 2, 1859, almost nothing was known about
    auroral activity. There had been speculation
    that it might be caused by meteoric activity, but
    no real evidence existed (Odenwald, 2008).
   Following these events, Scientific American, in
    their October, 15 issue stated that it was then
    “firmly established” that there was a connection
    between the aurora and electro-magnetic forces
    (Odenwald, 2008).
     The Solar “Superstorm” of 1859
   Studies since then have determined that auroral
    activity is the direct result of the solar ejection of
    plasma, which interacts with Earth's magnetic field.
   By studying ice-core samples it has further been
    found that this sort of “super” storm is not a one-
    time event, while the 1859 event was the largest
    for at least 450 years (Odenwald, 2008).
   Since then, much smaller solar events have
    caused damages in the billions of dollars.
    Satellites, cell phone communications and even
    entire power grids are at risk from even these small
    storms, much less the next “superstorm.”
     The Solar “Superstorm” of 1859
   While the damage from the 1859 event was limited
    to the fledgling telegraph system (then just 15
    years old), the damage from a storm of this size
    today would likely run into the trillions of dollars.
   A much smaller event in March, 1984, caused the
    Hydro-Quebec power grid in Canada to go down
    for over nine hours, with damages in the hundreds
    of millions of dollars (Savage, 2003).
   In studies by John Kappenman it was determined
    that an event the size of the September 1859 event
    would lead to the entire United States electrical
    grid shutting down, with recovery taking weeks, or
    even months (Odenwald, 2008).

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