10 Things You Didn’t Know About Light
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.
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.”
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 thanGalileo, 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.
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, thatm=(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. These waves of light — termed the aurora borealis and aurora australis (or northern lights and southern lights, respectively) — are typically green, but hues of blue and red can be emitted from atmospheric nitrogen atoms, as well.
5) Neutrinos aren’t the first things to apparently outpace the speed of light
The Hubble telescope has detected the existence of countless galaxies receding from our point in space at speeds in excess of the speed of light. However, this still does not violate Einstein’s theories on relativity because it is space — not the galaxies themselves — that is expanding away (a symptom of the Big Bang), and “carrying” the aforementioned galaxies along with it.
4) This expansion means there are some galaxies whose light we’ll never see
As far as we can tell, the Universe is expanding at an accelerating rate. On account of this, there are some who predict that many of the Universe’s galaxies will eventually be carried along by expanding space at a rate that will prevent their light from reaching us at any time in the infinite future.
3) Bioluminescence lights the ocean deep
More than half of the visible light spectrum is absorbed within three feet of the ocean’s surface; at a depth of 10 meters, less than 20% of the light that entered at the surface is still visible; by 100 meters, this percentage drops to 0.5%.
2) Bioluminescence: also in humans!
Bioluminescene isn’t just for jellyfish and the notorious, nightmare-inducing Anglerfish; in fact, humans emit light, too. All living creatures produce some amount of light as a result of metabolic biochemical reactions, even if this light is not readily visible.
1) It’s possible to trick your brain into seeing imaginary (and “impossible”) colors
Your brain uses what are known as “opponent channels” to receive and process light. On one hand, these opponent channels allow you to process visual information more efficiently (more on this here), but they also prevent you from seeing, for example, an object that is simultaneously emitting wavelengths that could be interpreted as blue and yellow — even if such a simultaneous, “impossible” color could potentially exist.
(Source: io9.com)
Solar eclipse
As seen from the Earth, a solar eclipse occurs when the Moon passes between the Sun and the Earth, and the Moon fully or partially blocks the Sun. This can happen only during a new moon, when the Sun and the Moon are in conjunction as seen from Earth. In a total eclipse, the disk of the Sun is fully obscured by the Moon. In partial and annular eclipses only part of the Sun is obscured.
The image above is the One of Eddington’s photographs of the total solar eclipse of 29 May 1919, presented in his 1920 paper announcing its success, confirming Einstein’s theory that light “bends”
A Brief History of Light
Mobile Laser Lab Creates Water Droplets in Moist Air
By Duncan Geere, Wired UK
Artificial rainmaking is an imprecise, environmentally hazardous process, but it could be made a little more eco-friendly with the addition of lasers.
A team from the University of Geneva has used a mobile laser laboratory to trigger the formation of water droplets in the air — a step towards being able to create rain. During 113 hours of firings, the cloud physicists discovered that pulses of laser light create nitric acid particles in the air, which serve as condensation nuclei for droplets.
Those droplets only grew to a few micrometers in size — too small to overcome air turbulence and fall out under the influence of gravity as rain. Typically, droplets need to be around a tenth of a millimeter to begin to fall. However, the effect of the lasers is significant enough for the physicists to pursue the work further.
Continue Reading “Mobile Laser Lab Creates Water Droplets in Moist Air” »
Oct. 21, 1879: Edison Gets the Bright Light Right
1879: Thomas Edison crowns 14 months of testing with an incandescent electric light bulb that lasts 13½ hours.
