A week ago, who among us would have guessed that light, the universe's ultimate speed demon, would be observed getting outpaced by a bunch of reckless neutrinos? Yes, these observations will obviously need to be checked and rechecked, but it just goes to show that you rarely know as much about something as you think you do.
So in the interest of keeping you all as educated on light as possible, here are ten little-known historical and scientific facts about everyone's favorite source of illumination.
10) Light can make some people sneeze
Between 18% and 35% of the human population is estimated to be affected by a so-called "photic sneeze reflex," a heritable condition that results in sneezing when the person is exposed to bright light.
The exact cause of the reflex is poorly understood, but people have been kicking around possible explanations for millennia; Aristotle, for example, chalked the reflex up to the heat of the sun on one's nose, while most modern-day scientists posit that a cranial nerve responsible for facial sensation and motor control (that is in close proximity to the optic nerve) picks up on electrical signals intended for the optic nerve and tells the brain that there is an irritant in the nose that needs to be cleared out.
9) Plato thought that human vision was dependent upon light, but not in the way you're imagining
In the 4th Century BC, Plato conceived of a so-called "extramission theory" of sight, wherein visual perception depends on light that emanates from the eyes and "seizes objects with its rays."
Plato's student, Aristotle, was among the first to reject the extramission theory and the idea of a so-called "active eye," advocating instead a passive, "intromission" theory of vision, whereby the eyes receive information via rays of light as opposed to generating these rays on their own. (Image via.)
8) Einstein was not the first one to come up with a theory of relativity
Many people associate "the speed of light" with Einstein's theory of relativity, but the concept of relativity did not originate with Einstein. Props for relativity actually go to none other than Galileo, who was the first to propose formally that you cannot tell if a room is at rest, or moving at a constant speed in one direction, by simply observing the motion of objects in the room.
What Einstein did do was bring Galileo's conception of relativity up to speed by combining it with Newton's work with gravity, and James Clerk Maxwell's equations addressing electricity and magnetism (equations, it bears mentioning, that predicted that waves of electromagnetic fields move at 299 792 458 meters per second — i.e. the speed of light).
7) E=mc^2 was once m=(4/3)E/c^2
Einstein was not the first person to relate energy with mass. Between 1881 and 1905, several scientists — most notably phycisist J.J. Thomson and Friedrich Hasenohrl — derived numerous equations relating the apparent mass of radiation with its energy, concluding, for example, that m=(4/3)E/c^2. What Einstein did was recognize the equivalence of mass and energy, along with the importance of that relevance in light of relativity, which gave rise to the famous equation we all recognized today.
6)The light from the aurorae is the result of solar wind
When solar winds from cosmic events like solar flares reach Earth's atmosphere, they interact with particles of oxygen atoms, causing them to emit stunning green lights like the ones captured by the International Space Station last week (featured here).