Understanding Light: Particle Theory, Take 1

1. 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, 2000)

2. Understanding Light:Wave Theory, Take 1 • Descartes supposed that light was waves, caused by disturbances in the “plenum.” (Smith, 1987) • 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)

3. 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)

4. 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)

5. 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)

6. 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).

7. 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).

8. 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).

9. 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.”

10. 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).