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9 posts tagged light

quantumaniac:

The Electromagnetic Spectrum
Our universe is rife with waves. Although the term Electromagnetic (EM) Spectrum may seem strange and distant - you’re much more familiar with it then you think! In fact, the spectrum is nothing more than the range of the different types of electromagnetic waves that are possible. Different types of waves are classified by their wavelengths and frequencies - if one changes, so does the other (they are inversely proportional). The longer a wave’s wavelength, the shorter it’s frequency - and thus it is less energetic. 
Radio - These have the longest wavelength of anything on the EM Spectrum. These are the types of waves that travel to your radio! However, these types of waves are emitted by many other things, not just your favorite radio station. Stars and gases in space emit these types of waves all the time. 

Microwaves - Slightly more energetic than radio waves are microwaves, which yes, are the types of waves in your actual microwave at home! Microwaves are frequently used in Radio Astronomy by studying the natural cosmic radiation in space. Microwaves can be captured and studied by setups like the Very Large Array shown below: 

Infrared - Next up is what enables night vision goggles to work! This is also known as thermal vision, because our skin emits infrared radiation! Infrared radiation detection is frequently used in military devices, and it is often used by astronomers to be able to see through thick regions of star dust!

Visible - This aptly named section of the spectrum is the part the humans can see. Every massive (mass containing) object that we can see emits visible radiation. A typical human eye can detect wavelengths of visible light from about 390-750 nm (nanometers). In terms of visible light, red is the least energetic (longest wavelength) and violet is the most energetic! 

Ultraviolet - This is one of the types of radiation that the sun emits, and what causes our sunburn! Ultraviolet (UV) is the type of radiation that occurs immediately before violet (ultra-VIOLET), because it has a shorter wavelength - similar to how infrared has a longer wavelength than red light (infra-RED). The hottest objects in the universe usually emit UV radiation. The visible parts of the sun’s radiation is not what burns us - it is the invisible UV radiation. 

X-Rays - These are the types of rays that doctor’s use to look at your bones! The man who discovered them, Wilhelm Conrad Röntgen, was awarded the first ever Nobel Prize in Physics for his discovery, in 1901. Very hot gases in the universe also emit harmful X-rays. 

Gamma Rays - These rays are the most energetic and powerful waves on the entire spectrum. Radioactive materials can emit gamma rays, and sometimes powerful particle accelerators, like those at CERN, can produce them as well. Only incredible violent and energetic events can emit gamma rays - such as supernovas or the collision of stars and galaxies. 

quantumaniac:

The Electromagnetic Spectrum

Our universe is rife with waves. Although the term Electromagnetic (EM) Spectrum may seem strange and distant - you’re much more familiar with it then you think! In fact, the spectrum is nothing more than the range of the different types of electromagnetic waves that are possible. Different types of waves are classified by their wavelengths and frequencies - if one changes, so does the other (they are inversely proportional). The longer a wave’s wavelength, the shorter it’s frequency - and thus it is less energetic. 

Radio - These have the longest wavelength of anything on the EM Spectrum. These are the types of waves that travel to your radio! However, these types of waves are emitted by many other things, not just your favorite radio station. Stars and gases in space emit these types of waves all the time. 

Microwaves - Slightly more energetic than radio waves are microwaves, which yes, are the types of waves in your actual microwave at home! Microwaves are frequently used in Radio Astronomy by studying the natural cosmic radiation in space. Microwaves can be captured and studied by setups like the Very Large Array shown below: 

Infrared - Next up is what enables night vision goggles to work! This is also known as thermal vision, because our skin emits infrared radiation! Infrared radiation detection is frequently used in military devices, and it is often used by astronomers to be able to see through thick regions of star dust!

Visible - This aptly named section of the spectrum is the part the humans can see. Every massive (mass containing) object that we can see emits visible radiation. A typical human eye can detect wavelengths of visible light from about 390-750 nm (nanometers). In terms of visible light, red is the least energetic (longest wavelength) and violet is the most energetic! 

Ultraviolet - This is one of the types of radiation that the sun emits, and what causes our sunburn! Ultraviolet (UV) is the type of radiation that occurs immediately before violet (ultra-VIOLET), because it has a shorter wavelength - similar to how infrared has a longer wavelength than red light (infra-RED). The hottest objects in the universe usually emit UV radiation. The visible parts of the sun’s radiation is not what burns us - it is the invisible UV radiation. 

X-Rays - These are the types of rays that doctor’s use to look at your bones! The man who discovered them, Wilhelm Conrad Röntgen, was awarded the first ever Nobel Prize in Physics for his discovery, in 1901. Very hot gases in the universe also emit harmful X-rays. 

Gamma Rays - These rays are the most energetic and powerful waves on the entire spectrum. Radioactive materials can emit gamma rays, and sometimes powerful particle accelerators, like those at CERN, can produce them as well. Only incredible violent and energetic events can emit gamma rays - such as supernovas or the collision of stars and galaxies. 

Reblogged from quantumaniac

alchymista:

Planet’s Glow May Shine Light on Possible Life
Earthshine is the sunlight that is reflected off Earth and reflected back by the moon, and while it may seem like this is simply just a pretty glow to be seen from other positions of the universe, some astronomers believe the shines of exoplanets could speak wonders about its potential for life.
These glows emitted by planets display imprints of the chemicals present in their atmospheres and the materials on the surface (as plants and rocks do not reflect light similarly). However, with their parent stars’ shines being infinitely brighter, detecting minuscule variations in glow within an exoplanet poses a dilemma.
By using a large telescope to examine our own polarized earthshine, Michael Sterzik and colleagues of the European Southern Observatory in Santiago, Chile, were able to distinguish the polarized light of planets from the unpolarized stars filling the sky. Through this team’s testing, they were able to confirm the technique’s accuracy, as their results concluded that Earth had “light signatures of oxygen, ozone and water, as well as an increase in reflected wavelengths characteristic of vegetation.” With even larger telescopes pointed outward, looking for these characteristics among exoplanets should be a viable possibility.

alchymista:

Planet’s Glow May Shine Light on Possible Life

Earthshine is the sunlight that is reflected off Earth and reflected back by the moon, and while it may seem like this is simply just a pretty glow to be seen from other positions of the universe, some astronomers believe the shines of exoplanets could speak wonders about its potential for life.

These glows emitted by planets display imprints of the chemicals present in their atmospheres and the materials on the surface (as plants and rocks do not reflect light similarly). However, with their parent stars’ shines being infinitely brighter, detecting minuscule variations in glow within an exoplanet poses a dilemma.

By using a large telescope to examine our own polarized earthshine, Michael Sterzik and colleagues of the European Southern Observatory in Santiago, Chile, were able to distinguish the polarized light of planets from the unpolarized stars filling the sky. Through this team’s testing, they were able to confirm the technique’s accuracy, as their results concluded that Earth had “light signatures of oxygen, ozone and water, as well as an increase in reflected wavelengths characteristic of vegetation.” With even larger telescopes pointed outward, looking for these characteristics among exoplanets should be a viable possibility.

(via theuniverseishuge-deactivated20)

Source alchymista

Reblogged from alchymista

intothecontinuum:

Here is something to think about that was only casually mentioned in passing in the recent video that was posted.

The sunlight you may or may not have experienced today finally managed to reach you after a ~100,000 year long journey since it was originally created at the Sun’s core!


Since the speed of light is finite, about 300,000,000 meters/second (or about 671,000,000 miles/hour), it takes time for it to travel from one point in space to another.

Given that the distance from Earth to the Sun is about 150,000,000,000 meters (about 93,000,000 miles) it takes about 8 minutes for light to reach us!

But this is just the time it takes light to reach us from the surface of the sun.

The light coming from the surface of the Sun is itself created as a by-product of nuclear fusion occurring deep in the Sun’s core.

Once light is created at at the Sun’s core it begins its journey to the surface of the Sun some 700,000,000 meters (430,000 miles) away from the core.

One might assume that this light takes the shortest path and heads straight to the surface, which would only take a couple seconds of travel time.

However, this is not the case because there is all kinds of star stuff that gets in the way.

An actual photon may only travel a mere fraction of a centimeter (anywhere between .01 and .3 centimeters depending on how close it is to the surface) before it makes a collision with other matter thereby diverting its path to some other random direction.

Photons continue moving in these seemingly random trajectories, bumping into other particles along the way, and don’t actually reach the surface until about 100,000 years later (give or take an order of magnitude)!

This kind of behavior characterizing the photons motion is modeled by something called a random walk, and is illustrated in a few different instances in the animations above.

Random walks have widespread applications through out the sciences and mathematics. The idea of random walks are even used in some computer algorithms to allow for more efficient solutions to some problems.

One particular application of personal interest, and a rather abstract generalization of the idea, is the quantum random walk, in which the superposition principle of quantum mechanics is used to put the trajectory into a combination of multiple possible trajectories to assist quantum computers in solving problems. The workings of Grover’s search algorithm can be thought of in this way. This isn’t the only instance that relates quantum mechanics to the workings of the Sun (see here).

Anyway, next time you are out in the relentless light of the Sun you may wonder what was going on some 100,000 years ago when that light first originated in the Sun, or maybe even where you’ll be 100,000 years from now when the light being created in the Sun at this moment finally reaches Earth.


(GIFs created from this Java app)


(via theehokeypokey)

Reblogged from intothecontinuum

the-star-stuff:

10 Things You Didn’t Know About Light
10) Light can make some people sneezeBetween 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 imaginingIn 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 relativityMany 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^2Einstein 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 windWhen 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 lightThe 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 seeAs 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 deepMore 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”) colorsYour 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.

the-star-stuff:

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.

(via earlgreybloke)

Source io9.com

Reblogged from the-star-stuff

Maxwell’s equations have predicted that the speed of light should be the same whatever the speed of the source, and this has been confirmed by accurate measurements. It follows from this that if a pulse of light is emitted at a particular time at a particular point in space, then as time goes on it will spread out as a sphere of light whose size and position are independent of the speed of the source. […] Similarly, the light spreading out from an event forms a 3-D cone in space-time. This cone is called the future light cone of the event. In the same way we can draw another cone, called the past light cone, which is the set of events from which a pulse of light is able to reach the given event.

Stephen Hawking, A Brief History of Time
14-billion-years-later:

Mechanoluminescence
Mechanoluminescence is a relatively broad term which covers the emission of light from materials due to mechanical forces. One such type of mechanolumienscence known as sonoluminescence (producing light from sound) I’ve already covered. In this post I will be detailing triboluminescence.Triboluminescence is the term for production of light through the breaking, tearing, scratching or crushing of a solid. It’s not fully understood but the theory goes that when breaking apart, or forming, chemical bonds some of that energy is released in the form of light. The difference here is that no chemical reaction is occuring, simply the breaking of structures through mechanical force.
A prime example of this is to get two pieces of quartz or similar crystals, turn off the lights and strike them together (something I used to do under my bed as a child). In fact this very process was used by the Uncompahgre Ute Native Americans of Colorado in ceremonial rattles made of buffalo hide and filled with quartz crystals which generated bursts of light when shaken.An example less dependent on local geology can also be done by smashing apart Life Saver candies as seen in the above image.

14-billion-years-later:

Mechanoluminescence

Mechanoluminescence is a relatively broad term which covers the emission of light from materials due to mechanical forces. One such type of mechanolumienscence known as sonoluminescence (producing light from sound) I’ve already covered. In this post I will be detailing triboluminescence.

Triboluminescence is the term for production of light through the breaking, tearing, scratching or crushing of a solid. It’s not fully understood but the theory goes that when breaking apart, or forming, chemical bonds some of that energy is released in the form of light. The difference here is that no chemical reaction is occuring, simply the breaking of structures through mechanical force.

A prime example of this is to get two pieces of quartz or similar crystals, turn off the lights and strike them together (something I used to do under my bed as a child). In fact this very process was used by the Uncompahgre Ute Native Americans of Colorado in ceremonial rattles made of buffalo hide and filled with quartz crystals which generated bursts of light when shaken.

An example less dependent on local geology can also be done by smashing apart Life Saver candies as seen in the above image.

Reblogged from 14-billion-years-later