Shadows

[Jordan14]

I have asked this in other forums but I don't get much of a response.

 

In what dimension does a shadow exist. I thought that as everything in our universe is made of atoms you could not construct a 2d object. However obviously a shadow is not comprised of atoms but of a deprivity of photons. You can measue the length and width of a shadow so is a shadow a truely 2 dimensional object. I don't think a shadow can have a volume. However thinking back how can a shadow exist in two dimensions because a shadow will lay across rounded objects and I think planar objects can not be twisted.

[YT2095]

as you stated it will wrap a 3d object, but also rem that a shadow outline is not as Clear cut you`de think, the outline is always "Fuzzy".

 

the "shadow" or darkness is the default, Light is the definer or difference maker

[ed84c]

if you had 4 dimentions and time then would a shadow be 3d?

 

Also I believe a 2d shadow to be 1d.

[Sayonara]

A shadow is a volume.

[Jordan14]

So does that mean a shadow is three dimensional. Beacause I thought like I wrote above a shadow is dimensionless as its nt actually an object just a lack of something so you cannot define a shadow as existant.

[swansont]

Mathematically a shadow is a projection.

[Dogtanian]

Mathematically a shadow is a projection.

Yes, what we see as a shadow is a projection of the 3-d area into which the light cannot get on to a surface.

I would go far to say the shdow is 2-d, even if it is bent over a 3-d object in 3-d space, here I would just take it would still be on a 2-d surface, only the surface wouldn't be "flat".

[Sayonara]

Mathematically a shadow is a projection.

What's the mathematical description for a projection?

[swansont]

What's the mathematical description for a projection?

 

In 1-D it's the dot product with the unit vector.

[srh]

I would think of a shadow as a volume, for convenience. I can see how it could be viewed as 2D, if you thought of it as just the outline on the ground, however a shadow, by your definition (depravity of photons), begins at the object which is causing the light to be blocked. So that would mean it starts at the object, traces out the objects shape through the air, until it hits another solid object, where it becomes most visible as the outline you see.

[Jordan14]

But can something that is not there (photons) exist in a dimension, is it possibleto say that.

[Sayonara]

You're confusing the issue. A shadow is not a volume of non-photons, it's a volume in which there are fewer photons than the surrounds.

 

Think of it in the same way you'd think of a bubble in water - it's a lack of wateryness, but it still has volume.

[Guest Doron Shadmi]

You're confusing the issue. A shadow is not a volume of non-photons' date=' it's a volume in which there are fewer photons than the surrounds.

 

Think of it in the same way you'd think of a bubble in water - it's a lack of waterness, but it still has volume.

[/quote']

I like your explanation Sayonara³, let me add that in order to get a shadow, we need a source of light and at least two objects where one of them is closer to the source of light then the other.

 

since no one of these objects is less then 3d (and even if they are 2d but not on the same plane) then the lack of light must be taken as a volume.

[swansont]

You're confusing the issue. A shadow is not a volume of non-photons' date=' it's a volume in which there are fewer photons than the surrounds.

 

Think of it in the same way you'd think of a bubble in water - it's a lack of wateryness, but it still has volume.[/quote']

 

Yes, but there can be a lot of photons in that volume, as long as they aren't hitting anything. e.g. a laser going through a dark, dust-free area. You'd never know the laser was there if it didn't hit anything. yet that area could be in a shadow from another light source, and have more photons than a non-shadow volume.

 

I think the shadow has to be the surface that isn't scattering many photons, not the volume.

[Jordan14]

Meaning that a shadow is not a 3 dimensional object but infact a the actual 3 dimension if you know where i am coming from

[Sayonara]

Yes' date=' but there can be a lot of photons in that volume, as long as they aren't hitting anything. e.g. a laser going through a dark, dust-free area. You'd never know the laser was there if it didn't hit anything. yet that area could be in a shadow from another light source, and have more photons than a non-shadow volume.

 

I think the shadow has to be the surface that isn't scattering many photons, not the volume.[/quote']

I don't know if Jordan14 considers a shadow with a laser shining through it to be the same case as 'just a shadow'.

[123rock]

A shadow is 2 dimensional because it is the absence of something, namely light, thus it is nothing. Since an actual shadow without photons would be perfectly black, then you will realize that the grey shadow that you are thinking of here is in fact tricking you and you should be thinking of the surroundings with a gap or black spot. A shadow is a representation of what isn't there, and is less lighted by its surroundings. This argument is similar as to what's at the surface of an atom, 2D right, so how can it exist?

[123rock]

A shadow is 2 dimensional because it is the absence of something, namely light, thus it is nothing. Since an actual shadow without photons would be perfectly black, then you will realize that the grey shadow that you are thinking of here is in fact tricking you and you should be thinking of the surroundings with a gap or black spot. A shadow is a representation of what isn't there, and is less lighted by its surroundings. This argument is similar as to what's at the surface of an atom, 2D right, so how can it exist?

[Dogtanian]

Maybe we are thinking of all shadows as being the same. Instead maybe we should think of shadows a being relative to a given light source. Then you can still have the laser passing through a 3-d shadow that is crated by a light bulb.

 

Actually...thinking about it more now, I see a shadow created by particular light source as a 3-d space in which if you palce an object anywhere in that space light from the source doesn't reach it. Even if the laser passing through this space hits the object the oblect is still in the shadow from the light source despite being lit up by the laser.

[Dogtanian]

Maybe we are thinking of all shadows as being the same. Instead maybe we should think of shadows a being relative to a given light source. Then you can still have the laser passing through a 3-d shadow that is crated by a light bulb.

 

Actually...thinking about it more now, I see a shadow created by particular light source as a 3-d space in which if you palce an object anywhere in that space light from the source doesn't reach it. Even if the laser passing through this space hits the object the oblect is still in the shadow from the light source despite being lit up by the laser.

[Sayonara]

This is how I see it:

 

The shadow cast by light source L from shape ABC is not the triangle BCX, it is the volume ABCX.

 

BCX is simply the intersection of ABCX and an unrelated surface.

 

Sorry about the crude diagram.

[Sayonara]

This is how I see it:

 

The shadow cast by light source L from shape ABC is not the triangle BCX, it is the volume ABCX.

 

BCX is simply the intersection of ABCX and an unrelated surface.

 

Sorry about the crude diagram.

[Jordan14]

Then do you beleive that in the 2nd dimension a shadowis two d etc etc? and if you do wot do you eleive the shadow of a 0 dimensional (dot) object to be

[Jordan14]

Then do you beleive that in the 2nd dimension a shadowis two d etc etc? and if you do wot do you eleive the shadow of a 0 dimensional (dot) object to be