Why does light bend?

No rest mass but never at rest

A photon is said to have no rest mass but it is never at rest. A photon is always traveling at or near the speed of light. I guess I fail to grasp how a rest mass can be obtained from a particle that is never at rest.

Since it can have charge and frequency and can impact other particles and interact with them displacing electrons and changing the rest state of electrons in atomic structure I would say that a photon do indeed have mass. Also that this mass in converted into energy due to the photon traveling at the speed of light.
 
..I would say that a photon do indeed have mass.

Yes, a crackpot would say a photon has mass.

btw, photons do not have a charge, but they do have electric and magnetic fields and these fields can interact with other fields.

You really have no idea what you're talking about.
 
So what would you say you are

Just what is your qualification to judge the value of anyone elses opinion?
 
Just what is your qualification to judge the value of anyone elses opinion?

The qualification of recognizing a crackpot.

That qualification is reserved for those who do not submit to the irrational. :D
 
Just what qualifies you as the judge?

Well I guess a straight answer to a straight question was just too much to expect.

Back to work
 
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phew, trying to follow everything here

ok, let's not ruin this thread by an useless discussion about who has the best school etc. As long as we all try to think our best....and teachother, it would be much nicer (could someone say this to sharon and arafat to...well, that's another forum)

but let's shine a light on the light-subject again.(damn, that's a baaaad joke)

with thx to Crisp:
the reason a photon can't have mass is because of this:
When a photon has mass, it will have to follow the rules for an object with mass trying to reach the speed of light.
this is impossible....it would take an infinite amount of energy and time to reach it. Hence something with mass can't travel at the speed of light, light does, so i can't have any mass.
well, for exact answer on this question, go to the other thread about the cart/hill question......there Crisp explains everything much better I could ever do :)

ok: for the sake I am gettin' something wrong, let me analyse THE discussion so far:
We could see the slit as a secondary spherical light source, which is probably caused by some spin-interaction...????

And about the interference, there isn't any interference, unless you would add a second slit, which will create a second spherical light source.....with only one slit/one lightsource this effect will never occur.

well....I am waiting for the spin-part :D
and....correct me if I am wrong 'bout something offcourse
 
theories change with time and added information

Not all of us are up to date on the current ideas of the time. When I went to highschool which is when this subject is most often taught the theory was that light has revalistic mass

m = E / c^2.


This definition gives every object a velocity-dependent mass.

The modern definition assigns every object just one mass, an invariant quantity that does not depend on velocity. This is given by



m = E_0 / c^2,


where E_0 is the total energy of that object at rest.

When I went to school several decades ago the first theory above was taught. Theory changes with new information and new observations.

They will no doubt change again within our lifetime. New measurements made with new technology that has yet to be invented will reveal things we never likely considered.
 
A better way of looking at this is to use the correct relativistic energy relationship:

E<sup>2</sup> = (m<sub>0</sub>c<sup>2</sup>)<sup>2</sup> + (pc)<sup>2</sup>

where m<sub>0</sub> is the rest mass, c is the speed of light and p is the relativistic momentum.

A photon has no rest mass, so m<sub>0</sub> = 0.

Put that into the equation and you get E=pc, or p=E/c. In other words, even though the photon has no rest mass, it still has momentum which depends on its energy.
 
I'll make it simple. Light is the basics of illusion... :D

Light has no mass. It has two different states: particle and waves. First "illusion"... :)
Depending on the state you are talking about, the properties of light will be different, in different perspectives. Second "illusion"...
Then, if you introduce gravity, which is the attraction of mass from a low to a high concentrated mass in space-time, you remember that light has no mass, thus... it can't be attracted at all (eventhough it is... :p). Third "illusion"...

Look around you. Everything you see is because the light is coming back from the atoms to your eyes. Imagine Trillions of atoms everywhere all of them releasing dozens if not hundreds of photons per second. Isn't that crazy? And still... it's our "reality"... :p

It all depends in your perspective. Depending on the angulum you look, the light will (bend) in a different color.

I guess to explain this we have to use the two states of light: particle and waves. Can anyone give some insights? This should solve the problem...

Love,
Nelson
 
Indeedy Tuthseeker

Light is of course a classical wave when you look at its bulk properties. One that obeys Maxwells Equations. Being as it is pure a electromagnetic wave there is no mass involved.

But according to QM waves can behave as particles. So light has a particle like behaviour where this particle is the photon.

So, how do we get photons with no mass?

If you look at the electron configurations of an atom each electron exists with a specific energy as dictated by the Pauli Exclusion principle. Basically, they are fermions. More correctly their wave functions are not allowed to be the same.

If the electrons gain energy by some method, by heating or collisions, the electrons 'jump' in energy by some discrete amount, a so called allowed transition. Some time later that electron can lose the increased energy and fall back to a lower energy state. The energy released is a photon. As this is purely energy we are talking about, no mass is involved.
 
This is one of the Big Questions

Indeed, energy can be converted to mass and vice versa. So what is mass and energy?

Seems simple, mass is errr, well, umm, mass I suppose. For that matter what is an electron? Why should it have a specific mass and yet a proton has more. What dictates this.

There is something more going on in Physics than we currently understand. Existing models are good at describing what happens but are far from explaining reality in fine detail.
 
Who does empty space bend and light does not

How exactly does the hard vacuum of space bend in strong gravity, having no mass at all but the light traveling through that space also having no mass will not bend.

That makes no sense to me at all. Surely the light is what bends and not space itself. Since hard vacuum has no mass at all it would not be attracted to or bend to a gravity body.

Unless you believe that the vacuum of space has an underlying medium such as the old pre special relativity, eather theory.

A strong energy field such as a photon some of which have a charge of more then 5MeV in the High Gamma range would be attracted to a gravity body and be deflected in their path.

The hard vacuum of space it self being bent by gravity forces. Explain how that would work.
 
betavoltaic,

That's an oooold discussion... between Einstein and one of his friends... :D
(I don't remember who anymore... :( I guess Planck...)

Today's concept:

Is Einstein's concept. The light bends in the vacuum because of warped space-time. The warped space time is created by the gravitational field of a celestial body. It's the concentration of mass that determines how much gravity and space-time we will have. In absolute vacuum, with no celestial body nearby, the light does not "bend".


Future's concept:

Is his friend's concept.

The hard vacuum of space it self being bent by gravity forces. Explain how that would work.
Click to expand...

If that's true...

Unless you believe that the vacuum of space has an underlying medium such as the old pre special relativity, eather theory.
Click to expand...

... then, that's true too.

We know that vacuum creates matter, so there IS something in the vaccum. This "something" may be creating the bending of the light.
But if the Vacuum is as vacuum as the air we breath, then all Astrophysics, Quantum Physics and Particle Physics needs reformulation.

I believe that's right. This would explain many things...
The Vacuum is probably a medium. It has substance...

But whatever it's, it's not physical...

Then, it's beyond Physics... ;)

Love,
Nelson
 
KOLUET (Kned's Own Locked Up Energy Theory)

about the energy-mass conflict. I would like to introduce you to KOLUET.

since we know an electron, with mass, is in fact some sort of energy package, creating a wave, it came up to me, it is rather similar to a photon, and nothing more than energy.

So, I am convinced of the idea, that if we 'unpack' mass more and more, we will finally see that mass is not more then locked up energy, in this form, energy is able to create 'gravity-fields'.

On a similar way energy can be locked up in vacuum, without creating 'gravity-fields'. This will be a perfect explanation for the space- bending effect, gravity attracts this energy of vacuum form, but this energy doesn't attrac mass itself.

Also, we have seen in history of space, that right after the big bang there was a certain accelarating expansion of universe (a theorie by Alan Guth I think) which is thought to be caused by energy that came free from the vacuum in some sort of way.

so there is one constant in Space: energy.
-Energy can create 'gravity-fields' but doesn't always.
-Energy 'moves' in waves.
-Energy can be locked up as mass (speed from 0 - c)
-Energy can be locked up as photons etc. (speed = c)
-Energy can be locked up in vacuum (speed 0 or more than c?)

Notice that I made this up myself....there will be numerous faults....many things aren't really science-based..but as far as my knowledge goes, it is a rather stable theory.

(btw, it still can't answer my first bending problem:))
 
betavoltaic

Unless you believe that the vacuum of space has an underlying medium such as the old pre special relativity, eather theory.

"...time and space are modes by which we think and not conditions in which we live"

"...entirely shun the vague word 'space' of which we must honestly acknowledge we cannot form the slightest conception"

The above quotes are from Einstein. What he is asserting is that space is not a fabric or medium in the sense that air and water are mediums. Space is actually a collection of physical events that make up the spacetime manifold and its geometry. In other words, space is made up of the contents of space; photons, electrons, particles, stars, galaxies, etc... and the events by which these materials interact. A collision of two particles or the emission of a photon can make up points in spacetime for example. The interstitial space between these events are simply not there so far as the physical world is concerned. This 'empty' space is entirely subjective and imposes no change of condition on matter.

So forget about rubber sheets and bowling balls. These are only used to help construct concepts, they are not the realities of space.
 
To quote Q

Gravity is caused by the warping of space due to the presence of mass. Therefore it is the path through space in which photons travel that is bent. The photons will travel this bent path making it appear as if light bends.
Click to expand...

What I am trying to understand is how as you say the space bends and not the light. What is space that it can bend. What it is about space that attracts or bends it in a gravity field?
 
The difficulty of understanding the space-bending is the fact that it is almost like a new dimension.

you should try to understand why you can NOT understand it :)
In a 2-dimension world, you would never be able to understand a 3rd dimension.

Visualize a piece of paper, with lines on it (2D), when we bend this paper, the 2D based life will still see it as 2D, without the bending, unless it IS bended.

what happens with us in 3D is that we live on a balloon like world, something sticks in this balloon, what causes the surface to bend. BUT, we will still see it in 3D, not bended.

In the warped space, it is similar, but can get just a bit of the 4th dimension by noticing the effects of it on light.....the curved path must relie on a warped space.

So, I am sorry to say, but further then understanding WHAT is bended and what it means is as far as you can get, WHY and HOW space is bended, noone knows that exactly.

Offcourse I still believe in my KOLUET :) (see a few post up)
 
What it is about space that attracts or bends it in a gravity field?

A gravitational field is the dynamic embodiment of space and time. In other words, spacetime is not a consequence of gravity, it is the gravitation field itself. Mathematically, there is no difference between what we call a gravitational field and what we identify as spacetime. A massive body will warp spacetime in it's vicinity in a way that depends entirely on its mass.
 
Light does not bend, space bends. Light simply follows a straight line through this curved space, so to us it appears as if the beam of light itself is bending. As far as the individual particles of light are concerned, they travel in a straight line all the time.
 
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