Talk:Shadow

message: I can be a shadow! Shadows are also colored in the absence of white light.  The only time when a shadow is exclusively shades of gray is under a single color of light.  Illuminate a room with a red light, and the shadows are exclusively gray.  Illuminate the shadows with a white light, and the shadows are green.  Where both lights are blocked, or in other words where the shadows intersect, they are gray.  Away from the intersection, where the red light is blocked the shadows are green and where the white light is blocked the shadows are red.  In other words, light colors shadows or brightens them, according to the complementary color of the light blocked to cast the shadow.  In the case of white and red lights, the complement of white is red; with white and green lights, the complement of white is green.  In the absence of white light, colored lights blocked by an opaque surface cast shadows in the colors complementary to the lights blocked.  For green light, red shadows; blue, orange; yellow, purple; intermediate light, intermediate shadows.  In the absence of multiple light sources, colored lights illuminate spaces where other lights are not blocked.  The red shadow cast by blocking white light in the above example, is not a shadow with the white light off, but it is illuminated in red.  oneismany 15:40, 12 November 2005 (UTC)
replies: text: Perhaps, but infrared (for example) behaves like ordinary light in that if you have a device for viewing infrared, you can notice a spot on a wall where you shine an infrared light.  Video cameras with infrared sensitivity often come with a small infrared flashlight, which I believe, works like a normal flashlight.  When you shine such a light at people's eyes, the light is reflected much like the "red-eye effect" for normal light.  oneismany 08:39, 25 January 2006 (UTC)
thread_title:  Colored Shadows 

message: Correction to “shadows contain no information and can exceed the speed of light”:
I propose that shadows contain information, namely the outline of the object casting the shadow.
Furthermore, I propose that shadows propagate at exactly the speed of light, and wish to back it up with the following thought experiment:
Let us say that a huge plate appeared between the earth and the sun, 3 light-minutes from us, completely eclipsing the sun.  It would take 3 minutes before we would see the plate, and thus three minutes before the sun would disappear behind the plate.  If shadow traveled faster than light, the Earth would be in shadow before then.  The result would be a ‘night-time’ Earth, with a ‘day-time’ sun in the sky.
However, I do not know the evidence backing the original claim, and am hesitant to make this change without general concent.
:I suppose you have to think of sideways movement of the plate, causing a faster movement of the shadow on Earth.--Patrick 04:57, 16 July 2005 (UTC)
replies: text: What is the purpose of this section? A shadow can move slower or faster than the object which casts it. There's nothing interesting about that. And it isn't a speculation that a shadow can move faster than light, it is just a simple fact. It is obviously in accordance with general relativity, because there's no mass or energy moving with a shadow. And a laser is not an object moving at lightspeed. Maybe a laser light, but a light usually doesn't cast shadows... I think that the section should be removed, or at least reformulated. Bertik 17:48, 14 May 2006 (UTC)
replies: text: This section seems to exist purely to advertise the linked-to website. I'm inclined to re-remove it, or at least reformulate it in a way that doesn't rely on a single thought experiment in an external source. -- nae'blis 14:53, 7 August 2006 (UTC)

text: The conclusion is incorrect. The shadow itself NEVER moves faster than c. Projecting a shadow over a distance faster than C is not moving anything faster than light, nor is it transmitting anything faster than light. There is NO communication or relation between the ends of the shadow, only between the light that is casting the shadow and the object that it is reflected (or the lack thereof) upon, which never moves faster than c. This is like sending two courier pigeons in opposite directions and saying that your pigeons are moving twice as fast. falsedef 00:45, 12 March 2007 (UTC)
thread_title:  FTL dispute 

message: In December, the section titled 'Faster than light?' was removed without discussion.  I am restoring it here, with small modifications.  If anyone wishes to debate its value, please do so before removing it. Oneismany
: What is the purpose of this section? A shadow can move slower or faster than the object which casts it. There's nothing interesting about that. And it isn't a speculation that a shadow can move faster than light, it is just a simple fact. It is obviously in accordance with general relativity, because there's no mass or energy moving with a shadow. And a laser is not an object moving at lightspeed. Maybe a laser light, but a light usually doesn't cast shadows... I think that the section should be removed, or at least reformulated. Bertik 17:48, 14 May 2006 (UTC)
replies: text: This section seems to exist purely to advertise the linked-to website. I'm inclined to re-remove it, or at least reformulate it in a way that doesn't rely on a single thought experiment in an external source. -- nae'blis 14:53, 7 August 2006 (UTC)
replies: text: The conclusion is incorrect. The shadow itself NEVER moves faster than c. Projecting a shadow over a distance faster than C is not moving anything faster than light, nor is it transmitting anything faster than light. There is NO communication or relation between the ends of the shadow, only between the light that is casting the shadow and the object that it is reflected (or the lack thereof) upon, which never moves faster than c. This is like sending two courier pigeons in opposite directions and saying that your pigeons are moving twice as fast. falsedef 00:45, 12 March 2007 (UTC)
thread_title:  Section removed without discussion 

message: I made an edit saying that the stuff I removed was already in the disambiguation and it was not. Just saying. 69.192.62.63 00:19, 28 April 2006 (UTC)
thread_title:  About my edit... 

message: What's the minimum ambient light necessary to cast a shadow? Say a dark-adapted eye, white background, no other lights around and rapidly moving caster (to activate the rods)?
Venus (mag. -4) supposedly makes easily seen shadows. Sagittarian Milky Way 02:31, 17 January 2007 (UTC)
thread_title:  Dimmest shadow 

message: Although popular internet rumor states otherwise, Einstien never stated, "There is no substance called darkness,dark is only the absence of light. It is the same with good and evil.Evil is the absence of god's holy light."
-source, http://www.snopes.com/religion/einstein.asp
I am deleting it for the time being.
KinAlpha 21:16, 23 January 2007 (UTC)
thread_title:  Einstien never stated... 

message: What is the basis for the definition of shadow to begin the article? I think most dictionaries define the word as the projection of darkness onto a surface. This is the first definition for the Encarta defintion. I think that at the very least it should be noted that shadow can be defined as either the projection, or the region of blocked light since both definitions are used in common parlance. This has a direct implication to the argument of whether shadows can move faster then light. If you define the shadow as the area of projected darkness, then it can move faster then light, but with the current definition on this site the shadow cannot move faster then light.
* I do not know who posted this - no name or date. But I must agree. A shadow is the projection on a surface of the shape caused by the obstruction of a light source. The three-dimensional volume where the light is obstructed is the shade. In the absence of a surface, you have shade, but no shadow. Ptilinopus (talk) 15:20, 4 July 2018 (UTC)
thread_title:  Definition of Shadow 

message: i have many times noticed this phenomenon  but really dont know the reason behind it.
actually what happens is whenever  two dark  shadows come very near(in most of the cases penumbra is almost absent  even  for sunlight) they  seem to be joined even if there is no joiming of two objects( particulaly i hv observed this when i bring my head near to some other person ) it looks like as if it have got srtreched towards other shadow. and usually this is observed during morning in presence of sunlight.not in the afternoons may be this is because morning sunlight has got more intensity at that particular time of day.while in artificial lights it cant be seen as those lights dont havr capability to form comparatively dark shadow region(umbra) much of penumbra can be seen in those lights..
 
if anybody  could answer to this phenomenoon why this happens  please sent it to  praveshlove@gmail.com  —Preceding unsigned comment added by 122.167.178.152 (talk) 04:59, 4 October 2007 (UTC)
thread_title:  attraction between  2 shadows 

message: The article does not explain negative and undefined shadows in trigonometry. These refer the shadows at night and shaows within a body. Anwar (talk) 10:41, 30 June 2008 (UTC)
thread_title:  Shadow at night/inside a body 

message: I gutted the "Time effects" section for the reasons given in Talk:Sunrise#Shadow.  Spiel496 (talk) 13:46, 7 August 2008 (UTC)
thread_title: Variation with time

message: Any ideas why the Shadow article will not load as of this timestamp?  I tried editing some things to see if I could make it work, but in neither Firefox nor IE will it load.  I can only see the page by manually typing in the URL for editing.  Strange doings! —GodhevalT C W 19:13, 20 October 2008 (UTC)
thread_title: Page won't load

message: Is a shadow an example of inverse proportion?  —Preceding unsigned comment added by 220.225.218.253 (talk) 08:30, 28 October 2010 (UTC)
thread_title: Inverse proportion

message: Should the word "theory" be replaced with "idea", as "theory" has a definite scientific definition and may not be appropriate here  — Preceding unsigned comment added by 81.132.144.198 (talk) 11:25, 16 September 2011 (UTC)
thread_title:  Mythological connotations 

message: Why using an active light source (street lamp) as an example?  — Preceding unsigned comment added by 79.223.1.37 (talk) 17:26, 17 November 2012 (UTC)
thread_title:  Baaaad Example 

message: Would shadow contain density? , Is it only a visualization? , would it be faster than light in some contexts? AceyArtezy (talk) 20:35, 26 July 2023 (UTC)
thread_title:  Does Shadow have density?