Does a shadow have mass?

hi Shai

I didn't read all of this thread so I'm sorry if somone else allready said this. I think some people would understand what you are saying better if you had used the word "impresion" rather then the word "shadow". You are saying that what exists outside our reality is creating an impresion on our space-time which we detect as particles with no mass. What people have said about a shadow being an absence of light and the mass of light/shadow dosen't relate to what your saying.
I think of it like this; Take a sheat of paper and imagine it's surface is our reality now take a pencil and push it's point against the bottom of the paper and you see the impresion on the other side.
What you are saying is suported by particle wave duality. In the two slits experiment when electrons are fired in a beam they spread out as if being influenced by something, they are not being influenced by each other it is possible they are influenced by something outside our reality.

[edit on 28-1-2005 by TruthResearcher2000]

A shadow is an absence, or at least a diminishing of light, so it's like asking if a hole has mass. If you can answer that question then you've solved it. Me - I say no, it doesn't have mass.

i admit to not having read the thread, which is terible ettiquette, but in case its still up for debate, heres the deal:

shadows are an absence of light, in both existance and definition. it is a spot where less light hits, hence it is less bright. you cannot move mass around simply by waving your hand. that would require mass to move at the speed of light which doesnt happen.

[edit on 1/28/2005 by Amorymeltzer]

Even a ten foot thick block of lead would allow neutrinos to pass through.

If we froze a nanosecond of shadow, and were able to weigh it in earths gravity, we would find something more than zero within the penumbra.

What needs to be accounted for is the total volume of the area within shadow. We would then have to either subtract the weight of all the molecules or do the experiment in a vacuum.

Interesting idea...what really came through for me, though, is the knowledge previous posters have about quantum physics and the structure of atoms and subatomic particles.

so? thats mass IN the area of the shadow, thats not mass of the shadow. if i put my computer on my desk, my desk doesnt gain mass, it just has more mass on it.

Naw...you're missing my point, it's not the shadow...its the volume of the shade. The shadow is what is not reflected light from a source being blocked...shade is what is between the blocker and the shadow.

no, i understand that, i just dont understand what that achieves in terms of giving a shadow/shade mass.

Within the area of the shade, there is always something, even if it is in a vacuum. There could possibly be captured, at any moment, a number of Neutrinos or perhaps even a Strange Particle. This thread touched on a number of others which may also be contained, without going into the more familiar arena of Gamma, Beta, Alpha, Neutron (etc).
These have either passed through the 'blocker' or are eminating from outside the area.

There is always something, and some particles do have mass.

right, i know, got that. i just dont see how that has any relevance other than there exists mass in a certain volume.

Interesting that the neutrino has been mentioned, there are some who claim it dosen't exist. The neutrino was invented to ac# for extra energey that special relativity exists but has never been detected. As for the neutrino detectors the same neutrino like behavior is detected when there is no blocker. Isn't it possible that the blocker simply isn't filtering out everything and that mass (energy) dosen't increase with speed.

Photons have mass as does light i'll try to explain why with a few equations.

I'm going to assume everyone knows about Einsteins whole photon or quanta theory. If you don't then heres the quick expla. Light performs or functions as does a wave (sinusoidal) and as does a particle. These particles travel along this wave function whatever it may be according to its wavelength and frequency (this is what makes different color's ect)

Everyone then agree's that these photons which make up this wave or 'beam' of light contain energy? If you don't agree to that please explain why.

According to proven science, not theoretical, the energy contained within these photons is equal to Planck's constant, h. Which is like 6.62x10^-26 or -34 Joules multiplied by seconds multipled by the beam of photons frequency.

You could stop right there and say photons have mass just because of unit Joules contained in the equation. One joule equals 1 kg times 1 meter squared per second squared.

1 kg = mass.

Furthermore, you all agree that the photoelectric effect is true? The giving off of electrons due to the energy of photons striking the surface of a material? This is where work functions come into play. Just think about this. If light did NOT have mass or photons did NOT have mass how would the photoelectric effect be true? How could something with no mass contain ANY energy to be able to be absorbed by the electrons, thus giving off the kinetic energy in work functions? AKA electron volts?

Another point to be noted is that photons have momemtum. Momentum is equal to the mass of an object times its velocity. Once again mass is seen associated with photons.

When i first read in this thread that light didnt have mass, it totally messed with my head (being hung-over doesnt help either) So i have to find this out before I freak

If you believe this is not true, or there's something wrong with what i'm saying please correct or comment.


Along with the topic of shadows. I believe that light travels partly through objects, is diffracted by objects, and is absorbed by objects so shadows are just the absense of light.

To see a shadow - It must be projected onto a surface.
Take away the surface and it would travel away forever and remain unseen and unknown to you.
With out the surface (mass) there is no shadow.
It is a ying/yang, observer/observed duality.

Ok I can tell you that a photon is a massless particle and carries with it energy and momentum. What is a photon, it is a quantum of the electromagnetic field, from our current understanding. A beam of photons applied to something will feel pressure. I know this because I have a relevant background. To answer the question, no a shadow does not have mass, even a light figure will not have mass. Well what do i know, no one knows.

I disagree...one can see earths shadow rising in the east as the sun sets. This shadow is called the Penumbra... I think (lol)
The point is that shadow is not invisible if it goes through a medium like air.

Wouldn't it be interesting to know the words of an astronaut, talking about the crispness of a shadow on the moon...or even the observations of an astronaut doing a space walk...how his shadow looks or whether he could see it stretch into infinity or not.

shadow is the subtraction of the absorption of the blocker from the total ambience of the radiant before it.

*makes an eagle with his hands*

A shadow is simply a lack or blockage of photons. Simple.End of story.

yes, I do have mass. My BMI is 37


on topic: I do not think its possible. Thats like saying "air has mass".

Umm, not quite. It is true that the SI unit of force (newton) and energy (joule) do use kilograms (mass), but that is does mean than it order to impart energy one must impart mass. A newton is the amount of force it takes to accelerate an object of 1Kg at a rate of 1 M/s^2. A joule is a newton multiplied by the distance the force is exerted.

For example - wiegh yourself, then get up and throw a ball - hard. You have probably just imparted several Joules into that ball. Now weigh yourself. Have you lost any weight? No. Has the ball gained any weight? No. But you have imparted a signifigant amount of energy on that ball.

Another way to think of this is that the unit also contains meters and seconds. Does that mean that the energy of an item is any way related to it's size or how long it has existed? Nope.

Unfortunately it's harder to clarify things when the error is not in the equations or math used, but in the fundamental concepts used.

What exactly is a 'shadow'? IF you mean the area between the object which blocks the primary light source and the area where the light emitted from (blocked by the object) haults, then yes. Are we talking about the optical illusion created by the background or between the area which blocks the primary light source and the background? If it is the area in between, then here on earth there must be atoms of air and photons between the two, correct?

Does a shadow HAVE mass?

Well yes it does.

This is not a mathimatical problem, or a physics, problem, or a metaphysics problem. It is symantic in nature.

In order for a shadow to EXIST it must be PROJECTED OR OUTLINED ONTO A SURFACE. all surfaces have mass. If the MASS (surface) did not exist then the shadow would not exist either. THE SHADOW HAS MASS.

Is a red apple really red? Actually it is every other color except red. RED is reflected. So the apple is not really red.

Western linear thinking just doesnt get it done.
see my point?

I love these type of questions and I am a big new fan of atss.

[edit on 31-1-2005 by a basket of kittens]